department of SOlar energyand environmental physics 1

Clockwise from upper left:

The effect of aeolian dustdeposition from duststorms such as this one, isbeing investigated by windtunnel simulations.

This 25m diameter,sun-tracking, parabolicdish was recentlyinstalled at theBen-Gurion NationalSolar Energy Center.

Sede-Boqer is one of 20stations around theworld selected forlong-term monitoringof solar radiation.

The ForestGoldman-SonnenfeldtBuilding is the newhome of the SolarEnergy andEnvironmental PhysicsDepartment.

2energy

physics

Department of SOlar Energy andEnvironmental Physics

Prof. Isaak Rubinstein, Chairperson

The Department of Solar Energy and Environmental Physics integrates disciplines of naturalsciences and engineering in the study of the physical environment. Its scientists come fromthe fields of geography, meteorology, mechanical engineering, applied mathematics, physicsand chemistry. Main topics of investigation include: solar energy utilization; applied optics;the desert climate; remote sensing detection and modeling of desertification; nonlineardynamics and thermodynamics as related to the environment; mechanics of granularmaterials; membrane electrochemistry and desalination.The department provides consultation services to government agencies and to municipalitieson the optimal use of solar energy in specific projects, and to industrial concerns on thedevelopment of novel solar devices.There are four research groups in the department: Desert Meteorology; Remote Sensing;Environmental Physics (Theory Group); and the Ben-Gurion National Solar Energy Center.

Phone: 972-8-659-6803 • Fax: 972-8-659-6921 • E-mail: lilianna@bgumail.bgu.ac.il

ACADEMIC STAFFBerkofsky, Louis (Professor Emeritus)Biryukov, SergeyBurde, Georgy Charach, Chaim1 (deceased, April 1999)Faiman, David1

Feuermann, Daniel Gitelson, Anatoly2

Gordon, Jeffrey M.3

Gutman, Lev (Professor Emeritus)Karnieli, Arnon2

Katz, EvgenyMeron, Ehud1

Offer, Zvi Y.4

Orlovsky, LeahPrigozhin, Leonid5

Rubinstein, Isaak5

Zaltzman, Boris5

Zangvil, Abraham4

Zarmi, Yair1

Zemel, Amos6

ASSOCIATE STAFFBerman, DavidIbbetson, Peter1 Joint appt. with BGU’s Dept. of Physics2 Joint appt. with BGU’s Dept. of Geology3 Joint appt. with BGU’s Dept. of Mechanical Engineering4 Joint appt. with BGU’s Dept. of Geography and Environmental Development5 Joint appt. with BGU’s Dept. of Mathematics and Computer Science6 Joint appt. with BGU’s Dept. of Industrial Engineering and Management

Time evolution of spatio-temporalchaos in a model of a chemical

reaction. The dark and lightshades represent chemical states

with different chemicalconcentrations. [Courtesy of Ehud

Meron]

3energy

physics

Research Activities

Desert Meteorology

The desert meteorology group investigates desert climates in general and the Negev desertin particular. Studies focus on the structure and dynamics of atmospheric circulation systemsand their variations in time and space – more specifically, the structure, motion andtrajectories of Mediterranean disturbances and the importance of the large-scale moisturefield in these processes; atmospheric fronts and their effect on rainfall in the region; watervapor recycling and its effect on climate; climate change and El Niño and their effect on theweather and climate in Israel. Researchers investigate how air circulation feeds cyclones withthe moisture necessary for rain formation, with emphasis on understanding the basicmechanisms and their influence on the hydrological cycle and climate change. This work ispart of the Global Energy and Water Cycle Experiment (GEWEX), a component of theWorld Climate Research Program. Special mechanisms of rain formation are studiedexperimentally and by mathematical modeling.

Another area of research is the interaction of atmospheric dust with ecological systems andstudy of the erosion, transport and deposition of atmospheric dust both by theoreticalmodeling and wind tunnel simulations (investigations which have practical applications inagriculture, solar systems efficiency, road transport and environmental preservation).Research topics also include dew formation, the variations of solar radiation and theoreticalmodeling of the atmosphere’s effect on heat stress in humans. Theoretical studies concerndifferent types of atmospheric instability and new explicit solutions to the Naviar-Stokesequations related to the atmospheric boundary layer and methods for the solution of partialdifferential equations.

At six major dust collection stations (Sede-Boqer, Shivta, Avdat, Mashash, Sayeret-Shakedand Beer-Sheva) in the Negev desert, members of the group conduct both routine andspecial meteorological and dust measurements at ground level and several meters aboveground. In collaboration with the Israel Meteorological Service the group is part of the globalBaseline Surface Radiation Network (BSRN). Sede-Boqer is one of 20 stations around theworld selected for long-term monitoring of solar radiation.

We constructed hydrodynamic models of atmospheric fronts and, on the basis ofclosed-form solutions of the problems of mature meteorological fronts, developed a newclassification of mature fronts in terms of only two dimensionless parameters. The model hasbeen evaluated qualitatively by comparing some characteristics of the model with thoseobserved for actual fronts. The comparison shows that the model provides a rational basisfor interpreting observations and classification of fronts.With: E. Morozovsky, Ben-Gurion University

We generalized the semigeostrophic, two-dimensional, uniform potential vorticityEady-wave model developed by Hoskins and Bretherton to embed the Newtonian (radiative)cooling. The observation that with this modification the potential vorticity varies in a knownmanner following fluid particles has provided the retention of the analytical representationof the solution. Our investigation indicates that the effects of thermal forcing may criticallychange the dynamics of semigeostrophic frontogenesis even though the damping timescalesignificantly exceeds the flow timescale. In particular, the formation of a frontal discontinuityfrom short-wave initial disturbances, with the wavenumbers beyond the short-wave cutoff ofthe adiabatic theory, becomes possible.

The effect of aeolian dustdeposition from dust storms such

as this one, is being investigatedby wind tunnel simulations.

Atmospheric fronts and

frontogenesis

Burde, Zangvil, Gutman

Frontogenesis in the

presence of thermal

forcing

Burde

4energy

physics

A comparative analysis:

disturbance tracks over

the Mediterranean Region

Zangvil

water vapor budget

components over

Central North America

and in Israel in relation

to precipitation

Zangvil

Observational and

theoretical studies of

water vapor and

precipitation recycling

Burde, Zangvil

The global Baseline

Surface Radiation

Network (BSRN)

Zangvil

Because of the impact of cyclones and cyclone tracks on local climate and the generalcirculation of the atmosphere, analysis of cyclone tracks has been a topic of continuing activeresearch in meteorology. The most widely used method in cyclone track analysis usedcenters of minimum pressure on surface synoptic charts. Sometimes centers of maximumrelative vorticity, or satellite cloud pictures have been used for that purpose. The problemwith these methods is that there is no clear distinction between stationary and transientdisturbances. For example, if track analysis is performed in the usual manner in the summerover the eastern Mediterranean region, only stationary low pressure systems appear incertain locations such as Cyprus or Iraq. We developed a method by which the stationarydisturbances are filtered out of the synoptic data and transient disturbances can bediscerned. We also study the connection of these disturbances with local weather. Verylarge data sets of meteorological variables at several elevations extending in time for twodecades over Europe and the Mediterranean were used in this comprehensive study.With: S. Karas, Ben-Gurion University

This investigation is part of an ongoing joint effort with the Cooperative Institute forMesoscale Meteorological Studies of the University of Oklahoma. The atmospheric moisturebudget of a given continental region is a complex function of the meteorological andhydrological processes within the region and surrounding areas, and of the soilcharacteristics and type of land use. We are studying the relationship between the differentmoisture budget components and precipitation. The main dynamical processes reflected inthe moisture budget are water vapor storage and the horizontal and vertical advection ofmoisture within the region. All these interact in several ways with the inflow and outflow ofwater vapor at the region’s vertical and horizontal (the earth’s surface) boundaries. In thisstudy we are performing calculations of the moisture budget components using measuredmeteorological data from a region of about one million km2 over the central USA andcomparing it with Israel and vicinity, in an effort to understand the above-mentionedinteractions.With: D.H. Portis, P.J. Lamb, University of Oklahoma

Generally, precipitation over a given region derives from both moisture advected into theregion by winds, and by moisture evaporating at the surface within the region. Thecontribution of local evaporation to local precipitation, called "recycling,” may provide afeedback mechanism between land surface processes and precipitation, which may bereflected in the moisture budget of the region. In this context, the contribution of localevaporation in a given continental region is studied by two different approaches –observationally, by extending the conventional moisture budget calculations, andtheoretically, by extending Budyko’s one-dimensional equation to two dimensions and byother theoretical considerations. We developed a fluid dynamics approach to thequantification of the precipitation recycling process, which allows for the role of atmosphericflow structure. The new approach improves the ability to estimate precipitation recycling,and also makes it possible to incorporate the atmospheric flow structure in the feedbackmechanisms in hydrological and climatological processes. With: P.J. Lamb, University of Oklahoma

The BSRN, a project that was initiated over 10 years ago, is an international network ofabout 20 meteorological stations that monitor the temporal variation of solar radiationreaching the surface of the earth at locations representing different global climates. Theinternational BSRN panel decided to locate one of its stations (which is run in collaborationwith the Israel Meteorological Service) at Sede-Boqer because: 1) Sede-Boqer is ideal forsolar radiation measurements in a remote desert location. 2) The meteorology group hasbeen collecting solar radiation and other meteorological data on a routine basis since 1981.These data are available on site. With: A. Manes, Israel Meteorological Service and the World Meteorological Organization

5energy

physics

Characterization of sky

conditions by the use of

solar radiation data

Zangvil

comparative analysis of

disturbance tracks over

the northern Red Sea

Zangvil

Dew measurements

in the Negev

Zangvil

Aeolian dust deposition

in the desert

Offer

A method has been proposed to characterize the sky and cloud conditions (SCC) by usingground-based global and diffuse radiation data. The term SCC is defined for the purpose ofthis study as the bulk effect of clouds and other atmospheric constituents on the values ofthe diffuse fraction of solar radiation (D/G) and the ratio between the global to extra-terrestrial radiation (KT). However, there is difficulty in using the measured values of thesetwo parameters since they are influenced by the solar zenith angle as well as bymeteorological factors. We overcame this problem by developing a semiempirical schemewhich removes zenith angle-dependent, seasonal and latitudinal variations of the aboveparameters, leaving only variations due to meteorological factors. The method isdemonstrated on monthly mean D/G-KT relations calculated from three years of global anddiffuse irradiance measured at Sede-Boqer. We found very good correspondence betweenmeasured sky and cloud conditions at Sede-Boqer and the D/G-KT relations as corrected byour method.With: P.J. Lamb, University of Oklahoma

This is a continuation and extension of the above-mentioned investigation of the behavior ofdisturbances and disturbance tracks over the northern Red Sea Region (Red Sea Troughs)and their influence on the weather in Israel.With: Y. Zvieli, Ben-Gurion University.

We analyzed dew measurements taken at Sede-Boqer for nearly 6 years and describedseveral parameters of dew formation. The total monthly amount of dew and the distributionof the number of dew nights shows two distinct maxima (in September andDecember-January) and two minima (in April and November). The average dew deposit perdew night behaves differently: the most striking feature is the appearance of distinct winterand summer regimes, with the winter having more dew per dew night. The average durationof dew per dew night appears to follow very closely the length of the night: there is a clearmaximum of dew duration in December (7.9 hrs) and a minimum in July (5.5 hrs). The rateof dew accumulation is found to have distinct dry season, and rainy season (winter) regimes.

Dust is an important component in the desert climate as well as in shaping the morphologyof the land surface. To study its effects, research was conducted by means of fieldexperiments and wind-tunnel simulations. In a 24-month experiment, aeolian accumulationof natural atmospheric dust in a desert environment was investigated. Dust accumulation byday was systematically higher than at night. Dust that accumulated at night was coarser thandust accumulated during daytime. The average monthly concentration and accumulation areconsiderably influenced by high-magnitude dust events, either dust storms or dust hazes. Thevelocity of accumulation, defined as the ratio between accumulation and concentration,varied between 1.18 m/s and 4.53 m/s.A study of aeolian erosion of natural dust was conducted on two types of hills, located in arocky desert, by means of field measurements and wind-tunnel simulations. Erosion wasmeasured along three transects: one across the elongated hill and two across the conical hill.In the field, erosion was measured on erosion plots during two wind storms. In the windtunnel, erosion was measured on topographic scale models. The wind tunnel experimentsand field experiments showed good agreement: Dust erosion was most pronounced on thewindward hill slopes, and more particularly on their upper part, close to the top. The highesterosion occurred at or immediately before the top. Downwind of the top, on the lee slope,erosion drops considerably. The areas that are most sensitive to wind erosion are accuratelypredicted in wind tunnel simulations.In addition, the spatial pattern of short-term aeolian dust deposition on and aroundcone-shaped hills was investigated by a wind-tunnel simulation of dust storms over atopographic scale model of a conical hill in the Negev desert. Conical hills create anelongated area of low deposition (“dust shadow”) in their lee. Downwind from the shadowzone, a local area of more-than-normal (compared to the undisturbed surroundings)deposition occurs. On the lateral flanks of the hill, and also on the small convex windward

Dust collection devices aremounted at different levels at the

Sede-Boqer meteorologicalobservation station.

6energy

physics

Airborne particle

dynamics: toward a

theoretical approach

Offer

Aeolian particle input to

the soil surface at the

northern border

of the Negev desert

Offer

exact solutions of fluid

dynamics equations

Burde

Extensions to

Lie group methods

Burde

Convective and

baroclinic instability

problems

Burde

slope just upstream of the top (and at the top itself), dust deposition remains low to verylow. It is the lowermost, concave windward slope that receives the largest amount of dust.With: D. Goossens, Leuven University, Belgium

Results of wind-tunnel simulations and field experiments indicate that airborne dust particlessettle on the windward side of hills whereas sand particle deposition is mainly observed onthe leeward side. That and other aspects, such as the existence of several deposition regimesrelating to wind intensity, call for theoretical explanations. We presented some preliminaryconsiderations leading to such a theoretical framework and also established the first stepstoward a general model of morphological changes of the relief under dust dynamics.With: L. Brenig, Brussels University, Belgium

In arid and semiarid regions, aeolian particle input is one of the major sources of soilnutrients. The particle input also improves the soil depth and strongly influences thewater-holding capacity of the soil. The measurements of the components of the aeoliandeposition and accumulation were carried out for 3 years (1992-1995). The average soilaccumulation for this period was 0.22 g/m2/d (80.64 g/m2/year). Significant differences wereobtained during the whole study period regarding the slope direction of the watershed.Almost all the granulometric analyses conducted on monthly collected samples showedsignificant amounts of clay-size and silt-size particles. Chemical composition of the airborneparticles showed that two major constituents, Si and Ca, dominate all the samples. With: E. Zaady, M. Shachak, BIDR

By applying a new approach for finding similarity solutions, we obtained a number of newexplicit solutions of the Navier-Stokes equations and the boundary layer equations. Many ofthe solutions are of interest from theoretical and engineering points of view.

Extensions to the classical and nonclassical Lie group methods have been developed. Theextensions produce symmetry reductions and solutions which are not obtainable by eitherclassical or nonclassical group methods.

A dynamic model of a spontaneous dust fallout intended to give a dynamic explanation of aspecial kind of dust storm has been developed. The model links this phenomenon with thenonlinear stage of the instability of the dust-laden stream. We also investigated the effects ofNewtonian cooling in baroclin stability on the basis of the Eady model and found new typesof dynamic behavior.

Remote Sensing

Remote sensing is a cost-effective method of gathering an enormous amount of informationon vast expanses of unsettled lands. Of particular importance is the study of environmentalproblems related to drylands, such as desertification and climatic change. Conventionalsurvey methods require considerable investments in manpower and are not always practicalin such areas.The remote sensing laboratory is an interdisciplinary research group. Its researchers developscientific theories, methodologies and applications in remote sensing, image processing andGeographic Information System (GIS) management of the earth’s resources. Working withother BIDR researchers, members of the group apply satellite, aerial imagery and grounddata to environmental problems, with special emphasis on drylands.The laboratory has two long-term collaboration agreements with NASA headquarters:1) routine monitoring of aerosol properties and surface spectral properties, and conductingshort field experiments that will relate these measurements to space observations;2) exploitation in research of ocean color data from the SeaWiFS program. This latteragreement enables the remote sensing laboratory to receive, store and analyze digital datafrom the SeaWiFS satellite.

Ground truth spectralmeasurements and multiband

photography used in field projectwith NASA to assess desertification.

7energy

physics

Remote sensing

techniques specific to

vegetation detection in

arid regions

Karnieli

Remote sensing of

desertification processes

Karnieli, Orlovsky

DAVID/MSRS

Karnieli

Detection of dust

over deserts

Karnieli

There are several difficulties in detecting and monitoring temporal changes in vegetationusing multispectral imagery from airborne or spaceborne sensors. These difficulties are dueto: 1) temporal change in the vegetation state; 2) temporal change in the soil/rock signature;and 3) difficulty in discriminating vegetation from soil or rock background. There are three ground features to be considered: i) the phenological cycle of perennialplants is related to their adaptation to the scarcity of water; ii) annuals, which are green onlyfor a relatively short period during the wet season and turn into dry organic matter duringthe summer; iii) microphytic communities (lower plants) of the biogenic crusts which arerapidly affected by moisture and turn green within minutes after the first rain. In aridenvironments, where the higher plants are sparse, the biogenic crusts have considerableimportance in the overall production of the greenness signal. In remote sensing,crust-covered areas are visually similar to bare soil throughout the dry period. Our findings show that the temporal analysis of natural vegetation in semiarid regions shouldtake into account the three ground features – annuals, perennials, and biogenic crusts – in away that is not commonly considered either in agricultural areas or in humid regions. In aridareas, the three phenological cycles should be studied separately. (From the remote sensingpoint of view, the biogenic crusts of microphytic communities can be considered as soilduring the dry season and as vegetation during the wet season.) We are calibrating andvalidating spectral models and remote sensing equations for maximum discrimination ofsparse arid and semiarid vegetation and ground features.

Spectral methods and image processing techniques are practical for assessing and monitoringdesertification processes, including vegetation and soil degradation, dune movements,salinization and dust loading over wide-ranging areas in different parts of the world. Researchis conducted in the Middle East as well as in Africa (Senegal and Burkina Faso) and CentralAsia (Turkmenistan, Uzbekistan, and Kazakhstan). Our studies examine current remotesensing methods to interpret how vegetation cover is affected by biogenic crusts ofmicrophytic communities in arid and semiarid regions.

We are developing new technology in an Israeli-German commercial small satellite for aninnovative application of remote sensing, namely, ‘precision agriculture’. Still in its infancy,precision agriculture is a holistic approach for micromanaging agricultural landscapes basedon the information received through this new technology.The payload, called DAVID (developed by OHB-Systems, Germany), will carry theMulti-Spectral High Resolution Remote Sensing System, (MSRS, developed by El-Op, Israel).The system’s main characteristics are 12 narrow spectral bands in the visible and nearinfrared regions, high spatial resolution, and high revisit time of three days. Our feasibilitystudies show that these features are ideal for developing precision agriculture anddetermining water quality of coastal and inland water bodies. We are developing and testing thecomponents of the system prior to launching the satellite, which is scheduled for the year 2002.

Dust is a dominant feature in satellite images, and is suspected to extract large radiativeforcing of climate. While remote sensing of dust over the dark oceans is feasible, adequatetechniques for remote sensing over the land still have to be developed. Here, similar toremote sensing of aerosol over vegetated regions, we use a combination of visible andmid-IR solar channels to detect dust over the desert. Analysis of Landsat TM images overSenegal taken in 1987 shows that the surface reflectance at 0.64 æm is between 0.54ñ0.05 ofthe reflectance at 2.1 æm, and reflectance at 0.47 æm is 0.26ñ0.03 of that at 2.1 æm,surprisingly similar to relationships in nondesert sites. We also found that dust has only asmall effect on the surface + atmosphere reflectance at 2.1 æm over the desert. Therefore,in the presence of dust, we use the Landsat TM data at 2.1 æm channel to predict the surfacereflectance at 0.64 and 0.47 æm. The difference between the satellite-measured reflectancesof surface + atmosphere and the predicted surface reflectances are used to derive the dustoptical thickness, t, at 0.64 and 0.47 æm. Results show that t can be derived within Dt=ñ0.5for the range of 0<t<2.5, thus enabling detection of dust sources and estimation of three to

8energy

physics

Optical properties of

higher plant leaves

Gitelson

Using AVHRR data for

quantitative estimation

of vegetation conditions

Gitelson

Remote sensing of

biomass and vegetation

status

Gitelson

Optical properties of

five levels of dust opacity over the desert. The method is very sensitive to the correctknowledge of the dust absorption, and is equally sensitive to dust in the entire atmosphericcolumn. It is best applied in the red part of the spectrum (around 0.64 æm) where dust wasfound to be weakl or nonabsorbing. We plan to use this method as part of the dustmonitoring from the Earth observing System MODIS instrument.With: Yoram J. Kaufman and Didier Tanre

In several related studies we developed models for analyzing the pigment content of plantleaves on reflectance and transmittance spectra. These are noninvasive techniques whichenable scientists to conduct wide-scale analyses of vegetation characteristics.By measuring reflectance and absorption spectra in visible and near infrared ranges, we wereable to estimate the chlorophyll content of several different nonrelated species fromdifferent climatic regions. We also developed a model for simultaneous retrieval of pigmentcontent (chlorophyll, caretenoids and antothyans) from the reflectance spectra of the leaves. These algorithms are simple ratios between percent reflectance at spectral regions that arehighly sensitive (540 to 630 nm and around 700 nm) to insensitive (near infrared) tovariations in chlorophyll content. The developed models predicting leaf chemistry from theleaf optics were validated for nine plant species in the range of chlorophyll content from 0.27to 62.9 (mg/cm2). An error of less than 4.2 (mg/cm2) in chlorophyll prediction was achieved.The use of green and red channels increases the sensitivity of Normalized DifferenceVegetation Index (NDVI) to chlorophyll content by about five-fold.With: C. Buschmann and H. K. Lichtenthaler, University of Karlsruhe, Germany; M. Merzlyak, Moscow StateUniversity

A Vegetation Condition Index (VCI) is a measure of weather impact on vegetation. Wedeveloped a VCI which measures weather impact on vegetation, and compares vegetationdensity, biomass and reflectance. For the first time it was shown that the VCI-derivedvegetation condition data can be effectively used for quantitative assessments of bothvegetation state and productivity (density and biomass) over large areas. Test fields werelocated in Kazakhstan, in several ecological zones with different climatic conditions, whereelevations range from 200 to 700 m and annual precipitation from 150-700 mm. The NDVIvariation ranged from 0.05 to 0.47. A determination coefficient between AVHRR (advancedvery high resolution radiometer) derived vegetation state and actually measured vegetationdensity of more than 0.76 was achieved.With: F. Kogan, NOAA/NESDIS, USA; E. Zakarin and L. Spivak, Academy of Sciences, Kazakhstan

We developed comprehensive remote technology to monitor vegetation status in terms ofphotosynthetic pigment concentration and vegetation fraction water content from satellites.The system gives us a considerable amount of information on plant physiology, including theability to detect the early stages of stress in vegetation. Most animals (including humans) usea green spectral range to sense the presence and vitality of vegetation. However, mostsatellite sensors use a combination of red and near infrared channels for that purpose. Thesesensors are not sensitive to the chlorophyll concentration in yellow-green to green leaves.We found (not surprisingly) the maximum sensitivity to chlorophyll concentration is aroundthe green band (from 520 to 630 nm and also near 700 nm). We developed the GreenAtmospherically Resistant Vegetation Index (GARI) which is sensitive to chlorophyll content,measures the rate of photosynthesis and monitors plant stress.Using the GARI, we investigated the reason for the repeatedly reported increase offluorescence ratio during the stress or damage-induced breakdown of chlorophyll in plants.The results demonstrate that at least more than 92% of the ratio variation in leaves duringdevelopment or at damage and stress events is determined by the variation in Chl contentand corresponding changes of the optical properties of leaves. We also developed atechnique for estimating pasture and crop productivity in semiarid zones using AVHRR data. With: Y. Kaufman, NASA Goddard Space Flight Center, Maryland; M. Merzlyak, Moscow State University;D. C. Rundquist, University of Nebraska-Lincoln

9energy

physics

phytoplankton and

remote sensing of

phytoplankton density

in productive waters

Gitelson

optimal management of

natural resources

Zemel

Most of the information pertaining to remote sensing of phytoplankton was developed foroligotrophic waters, where detritus and inorganic particles are scarce or theirconcentrations correlate with phytoplankton density. In our study we concentrated oninland and productive coastal waters, with the initial work done in Lake Kinneret, Israel. Theprimary objectives were: 1) to study the reflectance of different water bodies duringdifferent seasons of the year in order to find spectral features that are closely related tophytoplankton density; and 2) to devise and validate algorithms for chlorophyll estimationusing reflectance data as the measured variables. We devised optical models of turbid watersand found that the information gained from several spectral bands in the red and nearinfrared ranges of the spectrum allowed us to construct algorithms to estimatephytoplankton density. These algorithms were validated in Lake Kinneret and, with slightmodifications, in other environments: the polluted water of Haifa Bay (Mediterranean Sea),fish ponds and wastewater reservoirs in Israel, lakes with diverse trophic status innorthwestern Iowa, and lakes in Germany, Hungary and eastern Nebraska (USA).Within the context of information essential for estimating chlorophyll concentration byremotely operated instruments, we suggest that satellite sensors would be expedient toolsfor monitoring water quality and pigment content (chlorophyll, caretenoids andphycocyanin) in productive aquatic ecosystems. With: Y.Z. Yacobi, the Yigal Allon Kinneret Limnological Laboratory, Israel; J.F. Schalles, Creighton University,Omaha, NE; D.C. Rundquist, University of Nebraska, Lincoln

Environmental Physics (Theory Group)

Many processes and phenomena in science, technology and the environment, althoughseemingly different and unrelated, have common features when looked upon from themathematical-physical point of view. For example, the formation of sand dunes, river networksand the magnetic field in a superconductor have a common mathematical description that usessome very sophisticated mathematical tools. In a totally different arena, concentrators for solarradiation, special luminaires, certain aspects of the vision mechanism of living things, and theuse of solar radiation for solar surgery (instead of expensive lasers) are all applications of aspecial branch of optics called “nonimaging optics”. Another example is the commonmathematical-physical basis of water desalination and the physiology of living cells.The power of the mathematical-physical approach as a tool for describing and analyzingenvironmental processes is the raison d’être of the environmental physics group. Membersof the group are involved in topics related to environmental research including modeling ofclimatic phenomena in the desert, the interaction of dust particles with the environment andtheir effect on the climate, applied optics in relation to solar energy utilization, the analysisof nonlinear dynamic systems, modeling of desertification, water desalination, phase changeprocesses, applied thermodynamics and resource economics under uncertainty.To accommodate the interdisciplinary nature of environmental research, the group iscomposed of scientists with varied backgrounds in the mathematical and physical sciences.

The methods of dynamic optimization are employed to derive optimal policies for managingvarious environmental problems arising from the depletion of natural resources. Theseproblems include groundwater exploitation, energy policies, pollution control and theconservation of endangered species. The solutions include time profiles and steady states ofthe optimal processes. Comparing the solutions derived with and without environmentaluncertainty allows us to elucidate the effect of uncertainty on the optimal policies. Wecharacterized this effect in terms of the nature of the uncertainty (endogenous vs.exogenous), and of the environmental impact (reversible vs. irreversible). Our recent studiesconsider optimal R&D investments in alternative technologies (solar energy, desalination) toreplace conventional resources that are nearing depletion. At the present time solar energyand desalination technologies are expensive and used as alternatives mostly in certainsmall-scale situations, where fossil energy and fresh water are prohibitively expensive. Werecommend immediate, maximum investment in developing clean and efficient alternative

10energy

physics

Characterization of the

equilibrium structure of

dynamic optimization

problems

Zemel

Simultaneous vs.

sequential engineering

activities in risky R&D

projects

Zemel

Regulating

intertemporal public

projects

Zemel

Optical design and

radiative transfer

at the thermo-

dynamic limit

Gordon, Feuermann

technologies, so that these will be in place when the depletion of natural resources becomesa wide-spread, critical issue. With: Y. Tsur, Hebrew University of Jerusalem

Optimality conditions associated with dynamic optimization problems are typically described interms of a system of coupled differential equations that admit analytical solutions only under thesimplest specifications. The prevailing approach to analyse steady state behavior borrows heavilyfrom differential equation theory to explore the long-run behavior of the optimal pro-cesses. Inthis work we develop an alternative approach which does away with the dynamic equationsaltogether. Using a variational approach, we reduce the identification of the optimal equilibria tothe simple algebraic problem of solving the roots of a given function of the state variable. Theapplication of the method is illustrated by considering several resource exploitation methods. With: Y. Tsur, Hebrew University of Jerusalem

We consider development projects in which the activities can be classified in two types:uncertainty resolving R&D efforts which accumulate in the form of knowledge to eventuallygive rise to a discovery, and routine technical investments which aim at improving theprofitability of the project once the discovery has been made. The advantage of initiatingroutine preparatory activities prior to the achievement of a technological breakthrough insuch projects, sometimes termed "concurrent engineering," is analyzed within a suitabledynamic optimization framework. The optimal double expenditure policy is compared withthe conservative delayed investment policy, under which all the routine engineering activitiesare delayed until the risky R&D efforts culminate in a breakthrough. A criterion for theoptimality of the latter policy is developed on the basis of the probability distribution of thediscovery date. The application of the criterion is illustrated for a variety of specificationsregarding the uncertainty associated with the R&D process. We find that simultaneousinvestment is the optimal policy for a large class of probability distributions. However, if theconditional probability of immediate discovery is always below some critical value, it isoptimal to delay the preparatory activities until the discovery event.With: I. David and A. Mehrez, Ben-Gurion University

When private provision of a public good (such as the eradication of some source ofpollution) is a temporal process, regulation should provide the right incentives with regardto the timing of the project's activities and its duration. This task becomes involved forprojects that are indivisible or when monitoring the project's activities is costly. Wecharacterize optimal incentive schemes to regulate such projects, based on the projectduration (T) only. The mechanism consists of an auction to select the performing firm and aT-dependent payment schedule that induces the selected firm to carry out the projectaccording to the socially desirable plan. A dominant strategy implementation is offered. With: Y. Tsur, Hebrew University of Jerusalem

Many important optical systems are concerned with power transfer and brightness ratherthan with image fidelity. These applications include fiber optic coupling, radiant heating,projection, solar energy, illumination and detection. Nonimaging optics is a new designapproach that departs from the methods of traditional optical design to develop newtechniques for maximizing the collecting power of concentrator and illuminator systems.Nonimaging devices substantially outperform conventional lenses and mirrors in theseapplications. In fact, the performance of nonimaging devices may approach the theoretical(thermodynamic) limit. Practical nonimaging optical systems are now finding applications inmany of these areas. Their use promises higher efficiency, relaxed physical tolerances,heightened optical uniformity, and reduced manufacturing costs. Our research in this areaand our development projects with Israeli high-tech industries have generated new designsof both fundamental and commercial value, with special applications to remote lighting,infrared irradiation in the semiconductor industry, infrared detection and solar energy.With: H. Ries, Optics and Energy Consulting, Germany

11energy

physics

Biomedical optics

Gordon, Feuermann

Predictive, diagnostic

and optimization tools

for cooling devices

from irreversible

thermodynamics

Gordon

Solar energy

concentration

Gordon, Feuermann

Consultation for Israeli

high-tech industries

Gordon, Feuermann

Many minimally-invasive medical procedures involve the delivery of laser power inside thehuman body via optical fibers. There is considerable room for improvement in currentdevices, in the efficient coupling of laser light out of fibers and its uniform wide-angledistribution into human tissues. By foregoing conventional imaging optical systems andinventing nonimaging mirrors and aspheric lenses that are tailored to the specific needs oflaser fiber-optic surgery, we can now offer superior designs for a range of medicaltreatments.An especially novel advance is solar surgery, in which we recognized that in many importantlaser operations the expensive surgical laser can be replaced by an inexpensive novel solarconcentrator no more than 20 centimeters in diameter. Whereas no conventional lightsources can even approach the enormous power densities required for many surgicalprocedures and produced by lasers, the power density at the surface of the sun is adequate.Neither the coherence nor the monochromaticity of the laser is crucial in many operations:only the extremely high flux density. Our advanced optical design should be able toconcentrate sunlight to levels even higher than those at the surface of the sun and to channelthe power to the surgical target.

Using basic irreversible thermodynamics, we have developed analytical models for theperformance of a wide range of cooling systems (chillers). These models for air-conditioningand refrigeration devices allow the user to extract powerful diagnostic and predictiveinformation from a small number of noninvasive measurements that can readily beperformed in the laboratory or at the actual chiller installation. In the process, the behaviorof seemingly different types of cooling systems can be understood in a single universalthermodynamic framework. All modeling work has been supported and validated withextensive experimental data from commercial chillers. We have documented diagnostic casestudies for installed cooling plants, as well as manufacturer-driven optimizations of chillerconfigurations and operating conditions. Toward the end of 1999 Cambridge InternationalScience Publishing commissioned a new text, "Cool Thermodynamics", by J.M.Gordon andK.C. Ng, that presents the major progress in this area.With: K.C. Ng, National University of Singapore

We have proposed a paradigm shift in the way sunlight can be collected, concentrated anddelivered to remote receiving and conversion units: solar fiber-optic mini-dish systems. Theyoffer substantial advantages in efficiency, compactness, reduced mechanical loads, and ease offabrication and installation relative to conventional solar designs. The system’s building blockis a miniature solar dish (around 0.2 m in diameter) which concentrates sunlight into a singleoptical fiber. The fiber transports power to a remote receiver. Nonimaging second-stageconcentrators can boost flux levels to those approaching the thermodynamic limit.Considerable flexibility is gained in receiver design whereby one can now tailor solar opticsto receiver constraints rather than vice versa. Systems are modular and can be employed incentral or localized power generation from the kilowatt to the megawatt level. At the end of1999, the Israel Ministry of National Infrastructures awarded us a special grant for theexperimental realization of this new concept.With: H. Ries, Paul Scherrer Institute, Germany

We have worked with several Israeli high-tech companies in the development of assortedadvanced optical systems. The applications span: (a) medical diagnostic systems in radiologylaboratories and for the detection of peptic disorders; (b) the detection of micro-faults invisual displays; (c) the development of stationary solar energy concentrators for steamproduction and solar-driven absorption air conditioners; and (d) the design of special dryingsystems in the digital printing industry.

12energy

physics

Closed system

greenhouses

Feuermann

Perturbative analysis of

nonlinear systems

Zarmi

Quantitative aspects

of mass cultivation

of algae

Zarmi

Desalination:

Electroconvection in

electrodialysis

Rubinstein, Zaltzman

Diffusional mechanism

of strong selection in

Ostwald ripening

Rubinstein, Zaltzman

For better control of the climate in greenhouses, we are investigating a new type ofgreenhouse. To increase crop yield plants are fertilised with carbon dioxide. Quadrupling thecarbon dioxide concentration in the greenhouse atmosphere (compared to ambient air) canincrease crop yield by 30 to 150%. This is only possible if the greenhouse is closed, arequirement that is difficult to achieve due to overheating of the greenhouse. Shading aloneis insufficient and reduces the level of light necessary for plant growth. The new greenhousecladding removes a large part of the near infrared solar radiation (which the plants do notneed for photosynthesis) by means of a liquid radiation filter. This filter flows in the doublelayered roof of the greenhouse and acts as a solar collector for the near infrared radiation.New temperature-dependent material introduced into the filter produces a dynamic shadingdevice which can improve the greenhouse functioning. With: J. Gale, R. Kopel, and S. Levi, BIDR

The method of normal forms has been employed in the perturbative analysis of nonlinearsystems. Emphasis was given to the use of freedom of choice of the zero, as well as thehigher-order terms inherent in the expansion, for improving or simplifying the perturbativeapproximation. The approach was applied to the differential equation in the operatorrepresentation of the anharmonic oscillator. In addition, It has been shown that the freedomin the expansion is lost to a great extent in the method of Multiple Time Scales. The freedom in the expansion is applied to the analysis of the perturbed Burgers equation.With: Peter B. Kahn, State University of New York, Stony Brook

In reactors for mass cultivation of unicellular algae, the cells are forced to move back and forthbetween the illuminated and dark zones. This is achieved by means of air bubbles that are passedthrough the culture. The motion is random. We employed methods of stochastic processes foranalyzing the motion of the cells, as the distribution of the times they spend in both zones affectsthe biomass productivity of the reactor. Simple arguments have been developed for explainingthe observed increase of productivity, as well as the value of the optimal culture density.With: Amos Richmond, BIDR

This long-term research project concerns a theoretical and experimental study of ionictransport in electrolyte solutions in relation to membrane electrochemistry, in particular todesalination by electrodialysis. This includes the analysis of fluid dynamic instabilities arisingin these systems and the resulting nonlinear flows – specifically, electroconvection in strongelectrolytes. Our study focuses on the electroconvectional stability of a conduction state inan electrolyte layer adjacent to cation-permselective electrodialysis membranes. Theasymptotic analysis of the nonequilibrium double layer, developing at the membrane surfaceunder the passage of the ‘overlimiting’ electric current, was carried out and the relevantelectro-osmotic slip condition was derived. Thus far, this condition yields the only model forwhich it has been shown definitively that nonlinear electro-osmotically drivenelectroconvection may provide an efficient mechanism of overlimiting conductance throughthe electrodialysis membranes. In the experimental part of this research we distinguishedbetween the bulk electroconvection and electro-osmotic mechanisms of overlimitingconduction by studying concentration polarization at the cation exchange membranescoated by thin aqueous uncharged polymeric layers of variable thickness. This study showedthat the overlimiting conduction disappears at a coated membrane, suggesting that therespective convection in the diffusion layer is surface- rather than bulk-driven.

This research concerns the coarsening of particles of the condensed phase, at the late stageof the first order phase transition. This phenomenon, known as Ostwald ripening, is modeledby the classical Lifshitz-Slyozov-Wagner mean-field model. We showed through a systematicasymptotic analysis, that fluctuations (accounted for as a diffusional perturbation in theaforementioned model) provide a mechanism for the so-called ‘strong’ selection. This latterpicks a single limiting solution out of a one-parameter family of similarity solutions with afinite support, as the sole attractor of time evolution in the system.

13energy

physics

Thermodynamically

consistent schemes for

phase field equations

Charach

Solidification in binary

alloys: Capillarity and

solute trapping effects

Charach

Multiphase patterns in

periodically forced

oscillatory systems

meron

Vegetation patterns in

arid lands

Meron

The principal applications of this study are to the solidification of pure materials and binaryalloys. Thermodynamically consistent derivations of equations governing non-isothermalmelting/solidification processes were addressed. We allowed the gradient terms to bepresent not only in the free energy density and entropy but also in internal energy for bothnonconserved and conserved order parameter fields. Due to the gradient terms in internalenergy there exists a one-parameter family of alternative theories.

This research focuses on the development of kinetic phase diagrams for binary alloys. At verylow velocities the solidification processes are defined by the equilibrium phase diagrams.However as the growth rate increases both the liquid and the solid phases change. Suchdiagrams are of great interest in materials science and have various technologicalapplications.In addition, the phase diagrams are affected by capillarity undercooling at curved interfaces.In the frame of the present research we developed phase field models which predict thecapillarity and trapping of impurities in the process of crystal growth. We considered thatmodel accounting for gradient terms in the free energy and entropy account for nonlocalcontributions of both the phase field and the concentration fields. The later contributions arecorrelated with the growth of partition coefficient at sufficiently large velocities.

A conspicuous property of systems driven far from thermal equilibrium is the possibleappearance of persistent oscillations. Biological rhythms, like the heartbeat, provide goodexamples. The oscillatory systems encountered in nature are usually not isolated and quiteoften the interaction with the environment takes the form of a periodic forcing in time, as inCircadian rhythms entrained by the 24-hour day-night periodicity. Pattern formationphenomena in such systems arise due to multiplicity of phase states in various entrainmentresonances. These phenomena can best be studied using simpler case models, like oscillatingchemical reactions in controlled laboratory experiments.In 1997 Petrov, Ouyang and Swinney reported in Nature their observations of standing andtraveling wave patterns in a periodically forced oscillatory chemical reaction. Motivated bythese observations we studied oscillatory systems close to the onset of oscillations (or tothe Hopf bifurcation). We discovered a new front instability in even resonances, 2n:1 (n>1)(forcing frequency is about 2n times natural frequency). A stationary front, shifting theoscillation phase by π loses stability as the forcing strength is decreased past a critical valueand decomposes into n traveling π/n-fronts each shifting the oscillation phase by π/n. Theinstability within the 2n:1 resonance designates a transition from standing two-phasepatterns at high forcing strength to traveling 2n-phase patterns at low forcing strength. Anexperiment to test these predictions is being carried out by Swinney’s group in Austin.The current theory is based on an amplitude equation approach which is strictly valid only inthe vicinity of the Hopf bifurcation. The experiments on the oscillating chemical reaction,however, are not close to the Hopf bifurcation. We are currently investigating the effects ofthe distance to the Hopf bifurcation on front solutions and instabilities within variousresonances (3:2, 2:1, 3:1,4:1). We also plan to investigate the effects of shifting the systemfrom the oscillatory to the excitability regime.With: A. Hagberg, Los Alamos National Laboratory; H.L. Swinney, University of Texas, Austin; A. Yochelis,Ben-Gurion University

The low precipitation in semiarid and arid lands does not allow for complete coverage ofland by vegetation. As a result vegetation patterns appear. On hill slopes, patterns consistingof vegetation bands aligned perpendicular to the slope tend to form. On flat areas spotpatterns are more common. Band and spot patterns have been observed in Nigeria, Somaliaand many other places. We have constructed a model that reproduces these patterns. Themodel is being used to classify levels of aridity and to interpret desertification phenomenausing concepts of dynamical system theory. With: J. von Hardenberg, M. Shachak, and Y. Zarmi, Ben-Gurion University

14energy

physics

Pattern dynamics

in anisotropic

bistable systems

meron

bacterial crust growth

in arid lands

Meron

Modeling the phenomena

of population

segregation in urban

environments

meron

Catalytic surface reactions, involving adsorption and desorption of molecular species oncrystal surfaces, provide a special class of pattern-forming systems where processesoccurring on microscopic (nanometer) and macroscopic (micrometer to millimeter) scalesare coupled together: intrinsic crystal anisotropy affects diffusion on a micrometer scale,while adsorption of molecular species, controlled by macroscopic nonequilibriumconditions, may change or induce surface anisotropy.A common spatial structure appearing in surface reactions is a front separating domains withdifferent adsorbate coverages. The direction of front propagation may not be unique.Coexistence of fronts propagating in opposite directions has been observed in the catalyticCO oxidation on a platinum surface. This phenomenon has been attributed to a frontbifurcation that takes a single stable front into a pair of counter-propagating stable fronts.Similar bifurcations have also been found in bulk chemical reactions and in liquid crystals, andare known as nonequilibrium Ising-Bloch (or NIB) bifurcations.We studied the effect ofanisotropy on pattern formation in bistable systems undergoing nonequilibrium Ising-Bloch(NIB) front bifurcations. We found that anisotropy may induce front transitions leading toblob formation and to a state we term ‘stratified chaos’, characterized by strong correlationsalong one of the principal axes. The mechanism of stratified chaos is elucidated usingequations that describe the dependence of front motion on the direction of propagation.This study will be extended along the following lines: 1) understanding additional mechanismsof pattern formation resulting from anisotropy of diffusion; 2) applying theoretical results toexperiments on catalytic surface reactions; and 3) linking processes at a macroscopic scale(micrometer and above) to underlying processes at a microscopic scale (nanometer).With: M. Baer, MPI, Dresden; R. Imbhil, University of Hanover; M. Eiswirth, Fritz Haber Institute, Berlin; L. Pismen, Technion, Haifa

The microflora in arid lands often include thin crusts of microorganisms covering the soilsurface. One type of these crusts, consisting primarily of cyanobacteria, covers extendedparts of the Negev’s sandy soil. The crust stabilizes the soil against erosion, affects the waterregime and dryland ecosystems, and slows down sand-dune motion. We are in the course ofdeveloping a continuum model for the growth of bacterial crusts. The model consists ofnonlinear partial differential equations for the bacterial density, the surface wetness and thebacterial growth rate. The model will allow studying possible modes of crust growth(uniform, finger-like, etc.) and the effects of environmental factors such as precipitation.With: M. Baer, MPI, Dresden; A. Provenzale, Torino; J.von Hardenberg, Ben-Gurion University

Segregation phenomena in urban systems attract enormous attention by social geographers.One recent approach to studying urban segregation involves computer simulations of discretemathematical models. Implicit in this approach is the assumption of a hidden mathematicalstructure underlying the phenomena. The discrete models are too complicated to unravel thisstructure. In this study we propose a continuum modeling approach which is more amenableto analysis.We developed a specific model to address the dynamics of two distinct populationsin an urban environment where migration is dominated by socio-economic statusconsiderations. In addition to the two population densities, we introduced a third dynamicvariable representing the local socio-economic status. The model is suitable for studyingsegregation of new immigrants or foreign workers in veteran neighborhoods. The modelsuggests two forms of segregation. Weak segregation arising from a finite wave-numberinstability of a uniform mixed population state, and strong segregation involving interfacesseparating pure population states. It gives a mathematical interpretation of the tipping pointphenomenon and suggests two modes of population invasion, smooth and finger-like. Thepreliminary model discussed above assumes migration to nearby neighborhoods (e.g. becauseof community service conveniences). It is being extended to include nonlocal migration withinthe city (i.e. to distant neighborhoods). Further extensions will include stochastic elementsand additional variables like cultural affinity. We also plan comparisons of theoretical resultswith simulations on discrete models and possibly with real data.With: Y. Yizhaq, Ben-Gurion University

15energy

physics

Nonlinear dynamics of

aeolian sand ripples

prigozhin

Physics of surface

granular flow

Prigozhin

Air glow from the intensely

concentrated sunlight in the focal

region of sun-tracking, parabolic

dish (with receiver removed).

Aeolian sand ripples form regular patterns on coastal beaches and desert floors, indicatinginstability of the flat sand surface as winds transport and rearrange the loosely packed sand.Despite the significant progress in understanding the nature of sand ripples, major questionsabout the most interesting part of ripple formation remain open; these involve the nonlinearinteractions that follow the initial instability. We studied the salient features of sand rippleformation by means of a mathematical model that accounts for saltation and reptation [typesof movement] of sand grains. The linear stability analysis of this model confirms that ripplesgrow because of the geometrical effect of greater impact and ejection flux onupwind-oriented slopes than on downwind-oriented slopes. The rolling of dislodgedparticles down the surface slopes and scattering of ejected reptating grain trajectories by anuneven sand surface have a smoothing effect and tend to hinder the ripple growth. Taking allthese effects into account we were able to simulate not only the development of a typicalasymmetric ripple shape but also the evolution of sand ripple patterns characterized by theripple wave-length growth. We suggest that the coarsening of ripple array occurs not via asimple merger of ripples, as is usually assumed, but via soliton-like interactions with partialmaterial exchange between interacting ripples.

This area of research has recently attracted much interest among physicists, partly becauseit was realized that the rich and complicated behavior exhibited by the granular state ofmatter is still not well understood, partly due to the crucial role the granular materials playin various industries. We proposed a full-dimensional generalization of a popular BCRE model for the surfacegranular flow and dynamics of pile surface. It has been shown that in the long scale limit thismodel tends to the variational model proposed and studied in my previous works. This resultexplains why different models should be employed for, say, simulating formation of smallAeolian ripples and large dunes; it makes clear that the issue of scaling becomes mostimportant in this context and narrows the gap between current approaches to modelingsurface granular flows. The model for surface granular flows has been extended to flows ofpolydisperse materials accompanied by segregation of differing species. Free-surfacesegregation in size has been studied theoretically and experimentally. The model predictionsagree with the experimental results.With: B. Zaltzman, BIDR; H. Kalman, Ben-Gurion University

The Ben-Gurion National Solar Energy CenterProf. David Faiman, Director

The Ben-Gurion National Solar Energy Center houses five laboratories, each of which studiesone or more aspects of solar energy conversion.The Photon Energy Transformer and Astrophysics Laboratory (PETAL) is centered aroundthe recently-built 400 sq.m parabolic dish multi-purpose research facility. At this laboratorystudies are currently in progress towards the possibility of conducting concentratorphotovoltaics research during the day, and gamma ray astronomy at night.The Photovoltaic Advanced Materials Laboratory (PAMAL) performs research into novelmaterials with potential solar energy applications. Our current research efforts in thislaboratory focus on various methods to produce high-efficiency solar cells from fullerene, arecently-discovered form of carbon. The Parabolic Trough Laboratory (PATROL) contains a960 sq.m oil-heating loop of old Luz LS-2 collectors (currently being refurbished), and 2760sq.m of LS-3 collectors, with tilted axes, originally designed by Luz for direct steamgeneration. Current work at this laboratory aims at using the LS-2 loop to test some receivertubes, newly-developed by Solel Corp., and the LS-3 loop to investigate some system aspectsassociated with the use of these tubes. The outdoor Photovoltaic Test Laboratory (PVTEL)studies the aging of solar panels and associated system components under conditons of desertusage. In addition, the special climatic conditions at Sede-Boqer enable this outdoor facility tobe used for the performance of solar cell characterizations of unique precision.

t −−>

xSimulation of typical ripple

interaction, (region bounded by thediagonal, thin lines). Wind direction is

bottom to top. To show details, ripplesare stretched in horizontal direction.

16energy

physics

Photovoltaic research

with C60 crystals and

thin films

Faiman, Katz

Dry-cleaning for solar

collector surfaces

Biryukov

Direct observation

of clouds

Biryukov

The Meteorological Data Laboratory (MEDAL) monitors solar radiation in a variety ofspectral bands and geometrical configurations, together with a number of additionalmeteorological parameters. The laboratory is the base station for the ongoing NegevRadiation Survey, which aims at identifying optimal locations for future solar power plantsand establishing a data base of climatic parameters for their design.The Center’s current research program includes solar radiation studies, the use of novelmaterials for photovoltaic devices, photovoltaic module characterization, photovoltaicsystem design and testing, various aspects of solar-thermal research and dust preventionstudies. A number of research collaborations involve colleagues in Ben-Gurion University’sDepartment of Physics and other laboratories in Israel and overseas. The Center organizesand hosts a periodic series of Sede-Boqer Symposia on Solar Electricity Production. The 10thSymposium took place October 30 - November 1, 2000. The Center also runs a publicoutreach program in the form of audio-visual presentations and a guided tour of the systems.

Phone: 972-8-659-6934 • Fax: 972-8-659-6736 • E-mail: Sdann@bgumail.bgu.ac.il

This is an ongoing effort to fabricate solar cells from C60, the newly-discovered ‘fullerene’form of carbon. One aspect of this work involves the use of high-quality thin films of C60,which are grown in the physics department at Beer-Sheva (Prof. Shaul Goren’s group), usinga newly-developed technique of ours (Patent granted). The electronic properties of thesefilms are studied in Sede-Boqer, Beer-Sheva and at Tel Aviv University (Prof. Yoram Shapira’sgroup), and the films are used to make inorganic photovoltaic devices. Another aspect of thiswork, performed in collaboration with universities in Austria, Italy, the Netherlands, Spainand Sweden, involves the creation of "plastic" solar cells employing fullerenes embedded inconjugated polymers. (Funding: Ministry of National Infrastructures and The EuropeanCommunity).

This project is part of an ongoing study to develop an alternative to the use of water forcleaning the dust from the mirrors of solar power stations. We solved the problem of drydeposition by means of an electric field, which protects surfaces from airborne dust andcleans them (Patent granted). The method uses very little energy and is capable of cleaninglarge collector areas. The present part of the study addresses the problem of keeping wetsurfaces free of dust. (Funding: Ministry of National Infrastructures).With: S. Levy, BIDR

Current approaches to protecting solar power plants from the deleterious effects of suddensun-shading caused by passing clouds are ineffective. This is because the signals, indicatingthat action is necessary, appear as feedback only at the actual moment of shading. For theeffective smoothing of transitional effects, the correcting signal should monitor andanticipate cloud formation and movement. We solved the technical problem of how to viewcloud motion in the vicinity of the sun using a computerized video-camera. Then, usingalgorithms for image sequence analysis, we can precalculate, automatically, the moment ofshading. We are creating a computerized data base of cloud types and their manner ofevolution, together with an expert-system that will provide control instructions for theoptimal and safe operation of large solar power plants under cloudy conditions. A computer,armed with such a data base and expert-system, would periodically study video images of thesky from cameras situated in the vicinity of solar power plants, in order to provide real-timeoptimal control strategies for the plant operators. (Funding: Ministry of NationalInfrastructures).

17energy

physics

The overall goal is to use solar energy as a source of low-cost electric power. Our firstapproach will be to collect solar energy with "PETAL", our large (25m diameter),sun-tracking, parabolic dish concentrator, which is essentially a mosaic of relatively low-costglass mirrors, and to concentrate the energy onto a small photovoltaic power conversionunit, located at the focus. In order to do this, the light rays, reflected from the dish atconcentrations of the equivalent of several thousands of suns, must be deconcentrated anddistributed over the cell panel with uniform intensity, thereby achieving maximum efficiencyfrom the solar cells. This requires an unconventional optical technique unique design, theso-called kaleidoscope\de-concentrator, a concept which was developed for this project byProf. J.M. Gordon. Construction of PETAL commenced in early 1998. The working dish wasfirst turned on the sun in July 1999 and some optical characterization tests, using the moonand the planet Jupiter, were carried out at the end of the year [See Figure]. During theperformance of these checkout tests a number of design deficiencies were identified -particularly in the dish’s hydraulic system - which will need urgent attention. Investigation hasstarted (together with Prof. David Eichler of BGU’s Physics Dept.) into possibilities for usingthis parabolic concentrator as a major component of an atmospheric Cherenkov detectorwhich will record parameters for very energetic gamma-ray astronomy. (Funding: RashiFoundation; Ministry of National Infrastructures).

Work began during 1999, in collaboration with Solel Solar Systems Ltd, to refurbish the LS-2loop at Sede-Boqer and to rebuild the long-neglected Luz "DSG" system. The former will beused to test a number of newly-developed advanced components, whose system propertieswill then be studied in the DSG array. (Funding: Belfer Foundation and Rashi Foundation;Ministry of National Infrastructures).

Our studies involve PV modules which feed a variety of electrical loads (specifically, theelectricity grid or zenar diodes). Several times a year, the modules are disconnected fromtheir loads, cleaned, and characterized by a uniquely accurate method that owes its existenceto the natural AM1.5 spectrum (a climatic rarity) that exists at Sede-Boqer on clear days fora few hours around solar noon. This natural phenomenon allows us to measure cellefficiencies to an accuracy of ± 1%. In this manner, the time-dependence of moduledegradation due to such phenomena as the so-called "EVA-browning" can be quantified.During 1999 aging and stability tests began on several examples of new-technology PVmodules. These include multijunction amorphous Si, CdTe and CIS thin film cells. (Funding:Ministry of National Infrastructures).

This ongoing study involves (in addition to the routine monitoring of various parts of thesolar spectrum and maintenance of instruments), the development of calibration methodsand various instrument studies. It includes, specifically, the development of a calibrationtechnique for ultraviolet light sensors which permits hourly and seasonal corrections to bemade to instrument readings. (Funding: Ministry of National Infrastructures).

This is an ongoing study which aims to establish a data base of solar radiation componentsand other relevant meteorological parameters in order to permit the optimal design of solarpower plants of the future. Data are provided by the Meteorological Service, from 8 stationsin the Negev (Arad, Beer-Sheva, Besor Farm, Eilat, Hatzeva, Sede-Boqer, Sedom andYotvata), and processed into user-friendly form at Sede-Boqer. The survey’s purpose is toestablish a data base that will enable designers of future solar power stations to identifyoptimal sites for building the stations, and to predict their economic viability. A CD-ROM(published March 1999) contains a set of typical meteorological year files, based on up to 8years of data, for each site. In addition, the CD-ROM contains all of the raw data from eachof the sites through 1996, for those who wish to use this information for other scientificpurposes. (Funding: Ministry of National Infrastructures).With: A. Israeli, V. Liubansky and I. Seter, Israel Meteorological Service

High-flux parabolic dish

solar concentrator

Faiman, Biryukov

Rear-view of PETAL focused onthe moon.

Solar-Thermal Research

with Parabolic Trough

Collectors

Faiman

Photovoltaic Module

Stability

Faiman, berman

Monitoring and analysis

of solar radiation

in Israel

Faiman, Berman, Ibbetson

Data Processing for

Negev Radiation Survey

Faiman, Feuermann,

Ibbetson, Zemel

18energy

physics

This international collaboration involves the dissemination of information on PV systems inthe various member countries, and conversion of performance data from Israeli PV systemsinto a format compatible with a data base developed within the framework of theInternational Energy Agency Task 2 PV specialist working group. Task 1 includes gatheringand dissemination of information about PV systems and components in the various membercountries. Task 2 is concerned with performance data and analysis of PV systems in thevarious member countries. We prepare data on Israeli PV systems, insert the data into aninternational data base and perform comparative analysis of PV systems using an analysispackage developed by the working group. (Funding: Ministry of National Infrastructures).

Preparation of a data

base on the performance

of PV systems in Israel,

within the framework of

Israel’s participation in

the IEA Photovoltaics

Program Tasks 1 and 2

Faiman, Berman

A 1996 satellite photograph ofIsrael and it’s neighboring

countries. Israel is the geographiccrossroads of three dryland

regions. The Sahara-Arabiandesert belt extends across Egypt’swestern desert through the Sinaipeninsula, the Negev and Jordan.

The northern Mediterraneanregion extends from the coast ofthe PA’s Gaza Strip, through theIsraeli and Lebanese coasts. The

Asian steppes extend from centralIsrael northward through Jordan

and Syria.

Asi

an ste

ppes

S a h a r a - A r a b i a n

North

ern

Med

iter

rane

anI

SR

AE

LSede-Boqer

The sand dunes on the international border line between Israel and Egypt [arrow] change from a light whitishcolor to a slightly darker hew as they cross into the Negev, which is covered by a microbial crust on stabilizedsand dunes. This crust is an important natural element in the prevention of the expansion of deserts. Becausethe Negev is, by and large, closed to large-scale movement of people and herds, it is covered by the microbialcrust.

The microbial crust phenomenon is also relevant in developed countries. In areas that usually have quite a lotof rainfall and are cultivated intensively every year, the crust never forms. If a sequence of droughts occurs,since there is no crust on the topsoil, the dust is carried into the air, and can cause severe dust storms. The‘Dust Bowl’ was just such a phenomenon in the USA.

19energy

physics

Sergey Biryukov

Georgy I.Burde

David Faiman

Daniel Feuermann

Anatoly Gitelson

Jeffrey M. Gordon

Arnon Karnieli

Research Interests

Ph.D. Joint Institute for Nuclear Research, Dubna, 1995; Researcher Grade BApplied solar energy; System design and analysis of system performance; Influence ofenvironment on thermal and photovoltaic conversion efficiency; Aerosol physics;Hydrodynamics, electrostatics and electrodynamics of interactions between windborne dustand collector surfaces.Phone: 972-8-659-6737 • Fax: 972-8-659-6936 • E-mail: beryokov@bgumail.bgu.ac.il

Ph.D. Perm University, USSR, 1972; Associate ProfessorDynamic meteorology; Fluid dynamics (boundary layer theory, hydrodynamic stability,numerical methods in fluid dynamics, multiphase flows, environmental fluid dynamics); Heatand mass transfer, convective stability; Partial differential equations of mathematical physics.Phone: 972-8-659-6847 • Fax: 972-8-659-6921 • E-mail: georg@bgumail.bgu.ac.il

Ph.D. University of Illinois, 1969; ProfessorApplied solar energy; Radiation measurement; Spectral studies; Photovoltaic materials,devices and systems; Solar-thermal systems.Phone: 972-8-659-6933 • Fax: 972-8-659-6736 • E-mail: faiman@bgumail.bgu.ac.il

Ph.D. Ben-Gurion University, 1985; Researcher Grade BApplication of non-imaging optics to illumination and irradiation problems in high-techindustry. Analysis of closed system greenhouses. Energy in buildings. High-flux infraredradiation and solar energy concentrators - approaching the thermodynamic limit to opticalconcentration with practical, compact devices. Tailoring illumination optical systems toprescribed flux distributions at maximum radiative efficiency.Phone: 972-8-659-6927 • Fax: 972-8-659-6921 • E-mail: daniel@bgumail.bgu.ac.il

Ph.D. State University of Rostov, USSR, 1972; ProfessorPhysical aspects of remote sensing; Radiative transfer; Remote sensing of environment(ocean, coastal and inland waters, vegetation and atmosphere) in visible, near infrared andmicrowave ranges of the spectrum.Phone: 972-8-659-6858 • Fax: 972-8-659-6909 • E-mail: gitelson@bgumail.bgu.ac.il

Ph.D. Brown University, USA,1976; ProfessorApplied optics and radiative transfer: Solar energy - Development of new solarconcentrators based on nonimaging optics, ranging from low-concentration for stationarycollectors to dual-stage designs for very high flux devices. Biomedical optics - Design ofsculpted optical fiber tips for improving the efficacy and efficiency of laser surgery; Inventionof solar surgery and its prodigious potential for supplanting expensive surgical lasers; Designof optical systems for Israeli high-tech industries in medical diagnostic systems. Irreversiblethermodynamics: Development of universal predictive and diagnostic thermodynamicmodels for cooling systems such as reciprocating, centrifugal and absorption chillers. Newultra-high-efficiency designs for solar cooling. Illumination optics: Design and invention ofnew high-efficiency reflector shapes for lighting that also insure excellent angular control,involving the tailoring of reflector optics to prescribed target flux maps, for conventionallighting and infrared applications.Phone: 972-8-659-6923 • Fax: 972-8-659-6921 • E-mail: jeff@menix.bgu.ac.il

Ph.D. University of Arizona, 1988; Researcher Grade BRemote sensing: Spatial and spectral data analysis; Application of remote sensing toenvironment and earth resources problems especially in arid and semiarid regions;Geographic information system; Digital elevation model; Image processing.Phone: 972-8-659-6855 • Fax: 972-8-659-6704 • E-mail: karnieli@bgumail.bgu.ac.il

Eugene Katz

Ehud Meron

Zvi Y. Offer

Leonid Progozhin

Isaak Rubinstein

Boris Zaltzman

AbrahaM Zangvil

Yair Zarmi

Amos Zemel

20energy

physics

Ph.D. Moscow Institute of Steel & Alloys, 1990; ResearcherFields of Interest: Applied solar energy; Structural defects in semiconductors; Porous silicon;Photovoltaic materials; Fullerenes.Phone: 972-8-659-6739 • Fax: 972-8-659-6736 • E-mail:keugene@bgumail.bgu.ac.il

Ph.D. Weizmann Institute,1986; Associate ProfessorNonlinear dynamics; Pattern formation; Applications to physical, chemical and ecologicalsystems.Phone: 972-8-659-6926 • Fax: 972-8-659-6921 • E-mail: ehud@bgumail.bgu.ac.il

Ph.D. University of Bucharest, 1979; Senior LecturerGeomorphology; Relationship between the meteorological parameters, relief morphometryand airborne particles in the Negev Desert (deflation, erosion, transport, sedimentation,composition, aerosols, atmospheric pollution); Practical applications.Phone: 972-8-659-6849 • Fax: 972-8-659-6921 • E-mail: offer@bgumail.bgu.ac.il

Ph.D. Ben-Gurion University, 1995; Researcher Grade AFree boundary and variational problems; Numerical analysis; Models of dissipative systems;Granular Mechanics; Applied superconductivity.Phone: 972-8-659-6922 • Fax: 972-8-659-6921• E-mail: leonid@bgumail.bgu.ac.il

Ph.D. Weizmann Institute, 1978; ProfessorTheory of non-linear transport processes in continuous media mass and momentumtransfer in electrolyte solutions; Electrochemistry of synthetic ion-exchange membraneswith applications to desalination; Semiconductor transport; Chemical engineering.Phone: 972-8-659-6924 • Fax: 972-8-659-6921 • E-mail: robinst@bgumail.bgu.ac.il

Ph.D. Novosibirsk State University, Russia, 1989; Senior LecturerIncumbent of the Mendel Wasserman Career Development Chair in Desert StudiesTheory of continuous nonlinear transport processes in heat and mass transfer; Ionictransport in electrolytes and semiconductor transport, including free boundary problems inthese systems.Phone: 972-8-659-6928 • Fax: 972-8-659-6921 • E-mail: boris@bgumail.bgu.ac.il

Ph.D. University of California,-Los Angeles,1975; Associate ProfessorIncumbent of the Edward and Bertha Rose Chair in Desert MeteorologyDynamic and synoptic meteorology; Synoptic climatology; Rainfall; Relationships betweenrainfall and the large scale moisture field; Climate change; Connection between climatechange and synoptic mesoscale weather systems.Phone: 972-8-659-6845 • Fax: 972-8-659-6921 • E-mail: zangvil@bgumail.bgu.ac.il

Ph.D. Weizmann Institute, 1970; ProfessorIncumbent of the Phyllis and Kurt Kilstock Chair in Environmental Physics of Arid ZonesStochastic aspects of solar research; Nonlinear dynamics; Irreversible thermodynamicanalysis of heat and mass transfer processes.Phone: 972-8-659-6920 • Fax: 972-8-659-6921 • E-mail: zarmi@bgumail.bgu.ac.il

Ph.D. Weizmann Institute, 1981; Associate ProfessorStatistical properties of solar radiation; Dynamic optimization methodology and applications:Optimal exploitation of natural resources under uncertainty; R&D investment strategies inenvironmental projects; The relations between ecological and economic models.Phone: 972-8-659-6925 • Fax: 972-8-659-6921 • E-mail: amos@bgumail.bgu.ac.il

21energy

physics

PublicationsArkin, Y., C. Ichoku, A. Karnieli. Fault traces in an arid valley floor revealed by radar surface roughness classification, Arava Valley Israel. Canadian

Journal of Remote Sensing 25:302-310 (1999)Bär M., A. Hagberg, E. Meron and U.Thiele. Stratified spatiotemporal chaos in anisotropic reaction-diffusion systems. Phys. Rev. Lett. 83:2664-2667

(1999).Biryukov S., D.Faiman and A.Goldfeld. An optical system for the quantitative study of particulate contamination on solar collector surfaces. Solar

Energy 66:371 (1999)Burde, G.I. Semigeostrophic frontogenesis in the presence of Newtonian cooling. Jour. of Atmos. Sci. 56:3774-3788 (1999)Elphick C., A. Hagberg and E. Meron. Multi-phase patterns in periodically forced oscillatory systems. Phys. Rev. E59:5285-5291 (1999)Faiman D. Sizing PV systems for southern England: computing kWh from kWp. Proc. Instn. Civ. Engrs Mun. Engr 133:123 (1999) Fedotov A, N. Drozdov, E. A. Katz, Ju. Iliashuk, A. Mazanik and A. Ulyashin. Transformation of electrical activity of extended defects in silicon

polycrystals under annealing and hydrogen plasma treatment. Physica Status Solidi A171:353 (1999)Fedotov A, A. Masanik, E.A. Katz, Yu. Ilyashuk and A. Drozdovsky. Electrical activity of tilt and twist grain boundaries in silicon. Solid State Phenomena

67-68:15 (1999)Feuermann, D., J.M. Gordon and H. Ries. High-flux solar concentration with imaging designs. Solar Energy 65:83-89 (1999)Feuermann, D. and J.M. Gordon. Solar fiber-optic mini-dishes: A new approach to the efficient collection of sunlight. Solar Energy 65:159-170 (1999)Gitelson, A.A., J.F. Schalles, D.C. Rundquist, F. R. Schiebe, Y.Z. Yacobi. Comparative reflectance properties of algal cultures with manipulated densities.

J. Applied Phycology 4:345-354 (1999)Gitelson, A.A., C. Buschmann and H.K. Lichtenthaler. The Chlorophyll Fluorescence Ratio F735/F700 as an accurate measure of the chlorophyll

content in plants. Remote Sensing of Environment 69:296-302 (1999)Gordon, J.M., K.C. Ng and H.T. Chua. Simple thermodynamic diagrams for real refrigeration systems. Journal of Applied Physics 85:641-646 (1999)Gordon, J.M. and K.C. Ng. High efficiency solar cooling. Solar Energy 68:23-31 (1999).Ichoku, C., M.O. Andreae, T.W. Andreae, F.X. Meixner, G.Schebeske, P. Formenti, W. Maenhaut, J. Cafmeyer, J. Ptasinski, A. Karnieli and L. Orlovsky.

Interrelationship between aerosol characteristics and light scattering during late winter in an eastern Mediterranean arid environment. Journalof Geophysical Research 104:371-393 (1999)

Kahn, P. B. and Y. Zarmi. Time dependence of operators in anharmonic quantum oscillators: Explicit perturbative analysis. J. Math. Phys. 40:4658-4663(1999)

Karas, S., and A. Zangvil. A preliminary analysis of disturbance tracks over the Mediterranean Basin.Theoretical and Applied Climatology 64:239-248(1999)

Karnieli, A., G.J. Kidron, C. Glaesser and E. Ben-Dor. Spectral characteristics of cyanobacteria soil crust in semiarid environment. Remote Sensing ofEnvironment 69:67-75 (1999)

Katz, E. A. Fullerene-based thin films as a novel polycrystalline semiconductor. Solid State Phenomena 67-68:435 (1999)Katz E.A., A.I. Shames, D. Faiman, S.Shtutina, Y. Cohen, S. Goren, W. Kempinski and L. Piekara-Sady. Do structural defects affect semiconducting

properties of fullerene thin films? Physica B:273-274:932 (1999)Prigozhin, L. Nonlinear dynamics of Aeolian sand ripples. Phys. Rev. E60:729 (1999)Meron E. Self-organization in interface dynamics and urban development. Disc. Dyn. Nat. Soc. 3:125-136 (1999)Merzlyak, M.N., A.A. Gitelson, O.B. Chivkunova, and Y.R. Rakitin. Non-destructive optical detection of pigment changes during leaf senescence and

fruit ripening. Physiologia Plantarum 106:135-141 (1999)Primicerio M., I. Rubinstein and B. Zaltzman. Electrodiffusional free boundary problem in a bipolar membrane (semiconductor diode) at a reverse

bias for constant current. Quarterly Appl. Math. 57:637-659 (1999)Rubinstein I., and B. Zaltzman. Electroconvective mechanisms in concentration polarization at electrodialysis membranes. In: Membrane Surfaces (Ed.

T.S. Soerensen) Marcel Dekker pp 591-621 (1999)Rubinstein I. and B.Zaltzman. Diffusional mechanism of strong selection in Ostwald ripening. Phys. Rev. E 61:709-717 (2000)Saltz, D., H.Schmidt, M. Rowen, A. Karnieli, D. Ward and I. Schmidt. Assessing grazing impacts by remote sensing in hyper-arid environments. Journal

of Range Management 52:500-507(1999)

22energy

physics

Technical staff

Secretarial staff

Visiting Scientists

Postdoctoral Fellows

Graduate Students

Department of SOLAR Energy and Environmental Physics

Dov BokovzaSvetlana GillermanMali EIchlerShlomo KabaloDavid KlepachMelincheck Volodya

Mazal AdarShoshana DannLilian Na’aman

Bjarne Andresen, University of Copenhagen, DenmarkJerzey Cierniewski, Agricultural University, Poznan, PolandRay Dicker, AustraliaCornelia Glaesser, Martin Luther University, GermanyDirk Goossens, Agricultural University, Wageningen, the NetherlandsGarik Gutman, NASA/HQ, USA.Peter B. Kahn, State University of New York, Stony Brook, ,NYHelmut Lichtenthaler, University of Karlsruhe, GermanyMark Merzlyak, Moscow State University, RussiaRachel Pinker, University of Maryland, USAHarald Ries, Optics and Energy Consulting Inc., Munich, GermanyMarcus Salazar, University of Bourgogne, France

Jost von Hardenberg, Torino, ItalyCharles Ichoku, Universite Pierre et Marie Curie, France

Yael Cohen Giorgio Dall’Olmo Wiessam Essa Stefanie Herman Svetlana KarasErik Moderegger Kathy Pearlmutter Zhiaho Qin Shmuel SchijvargHeike SchmidtRobi StarkLouis TraoreYehezkel YizhaqArik YochelisBayarjargal YuAlex WekslerHagit Zioni Yoav ZurYossi Zvieli

MARCO AND LOUISE MITRANIDEPARTMENT OF DESERT ECOLOGY2Clockwise from upper left:

The ibex (Capra ibexnubiana) lives in themountains of the Negev,in the Rift Valley andJudean desert.

Black widow spiders(Latrodectus revivensis)are a dominantcomponent ofweb-building spiders inthe Negev highlands.

Bacteria that usepolyethylene as their solecarbon source mayprovide a solution todisposing of polyethylenewaste used in protectedagriculture in the AravaValley.

The poplar (Populuseuphratica) is found atwater sources all overIsrael and a few places inthe Negev highlands,including Ein Avdat inNahal Zin.

desertecology 24

MARCO AND LOUISE MITRANIDEPARTMENT OFDESERT ECOLOGY

Prof. Berry Pinshow, Chairperson

Researchers in the Mitrani Department of Desert Ecology use deserts as model ecosystemsfor advancing the study of ecology in general, and the ecology of Israeli deserts in particular.Our findings can aid the conservation of desert ecosystems and can be applied to theprudent and sustainable development of desert regions. A major departmental project deals with the conservation and maintenance of biodiversityin arid lands. This research includes studies to assess environmental heterogeneity (bothphysical and biological), ecological transformations (natural and man-caused), and bioticinteractions (such as predation, parasitism, and competition for resources). The roles ofscale and the mechanisms involved in creating and maintaining the diverse patterns of variousdesert plants and animals are also major topics of investigation.Research conducted by departmental staff and students includes investigations inphysiological ecology, behavioral ecology and life histories, population ecology and genetics,and community and landscape ecology. Studies in applied ecology, in collaboration with theJewish National Fund and other organizations, investigate the implications of regionaldevelopment projects, methods of arresting desertification, and the rehabilitation oflandscapes degraded by human activity. The Mitrani Department facilities include an animal care unit, a reference herbarium, areasfor garden experiments in loess and sandy desert soils, outdoor insect houses, and researchsites representing a variety of desert habitats. Three peripheral research centers areaffiliated with the Department: The Ramon Science Center (Mitzpe Ramon), the HatzevaResearch and Development Center (Hatzeva, Arava valley), and the Jewish National FundDesertification and Restoration Ecology Research Center (Sede-Boqer Campus).

Phone: 972-8-659-6771 • Fax: 972-8-659-6772 • E-mail: mitrani@bgumail.bgu.ac.il

Academic StaffAbramsky, Zvika1

Ayal, YoramBouskila, Amos2

Kotler, Burt P.Lubin, Yael D.Novoplansky, ArielPinshow, Berry1

Safriel, Uriel N.Saltz, DavidShachak, Moshe Ward, DavidZiv, Yaron2

ASsociate StaffYarom, Ilan Zaady, Eli

1 Joint appt. with BGU’s Dept. of Life Sciences2 Home department – BGU’s Dept. of Life Sciences

Poplar tree (Populus euphratica)at Ein Avdat near the Sede-Boqer

Campus.

desertecology 25

Carbon isotope ratios in

exhaled CO2 indicate

metabolic substrate use

and therefore past and

present diets in birds

Pinshow

Effects of fasting on

in-flight fuel catabolism

of pigeons

Pinshow

Nitrogen requirements

of an old world

nectarivore, the

orange-tufted sunbird

Nectarina Osea

Pinshow

Research Activities

Physiological Ecology

Desert organisms often have specialized physiological responses that are not observed inspecies residing in temperate climates. Currently, studies by Department researchers focuson the respiratory physiology, water loss, and energy budgets of desert birds and smallmammals. Although migrating birds are not necessarily adapted to arid-land conditions, theyare also of interest as hundreds of species make desert stopovers during their annualmigrations. In this context studies on birds have focused on the physiological limitations onlong-distance flight. Other physiological aspects of bird migration are also studied.

We hypothesized that an animal’s past and present diet can be distinguished through the13C/12C signatures of dietary components found in exhaled CO2. We tested our hypothesisby feeding 12 pigeons corn (a C4 plant) for 30 days, after which their breath 13C was –13.63‰ (± 0.30). We then fed 6 of them wheat (a CO3 plant) while the others continued toeat corn. After 48 h the exhaled 13C from corn-fed pigeons was unchanged, while that fromwheat-fed pigeons was –20.5 ‰. Three wheat-fed pigeons were then fasted for three days,after which their exhaled α13C was –14.96 ‰, while it was –13.57 ‰ in corn-fed pigeons,and –22.22 ‰ in pigeons fed only wheat. Thus, it is apparent that 13C/12C ratios of exhaledCO2 can be used to make inferences concerning metabolic substrate and hence present diet,past diet, and changes in diet from past to present. Breath CO2 analysis can be accomplishedwithout harming the animal or having to recapture it successively and is applicable to rareand endangered species. (Funding: United States-Israel Binational Science Foundation).With: Kent Hatch, Ben-Gurion University

Some birds regularly undergo extended fasts and many maintain high-metabolic activity, suchas migratory flight, while fasting. We investigated the effects of fasting on energy substratemetabolism in flight by depriving trained tippler pigeons (Columba livia) of food for 2 - 48 hpreceding flights of 4 h. Immediately after flight, blood concentrations of uric acid andb-hydroxybutyrate were increased, indicating elevated protein and lipid catabolism duringflight. Lighter birds and birds fasted for longer periods before a flight lost less mass during a4-h flight than heavier ones and ones that fasted for shorter periods. Birds that lost morebody mass during flight had lower blood b-hydroxybutyrate concentrations, suggesting lowerin-flight lipid oxidation. Flying pigeons apparently did not compensate for lower lipidcatabolism with increased proteolysis. Changes in in-flight protein catabolism were notcorrelated with either fast duration or pre-flight body mass. We reasoned that pigeons lostmore mass in-flight after feeding than after fasting because recently fed birds catabolizedmore glycogen. Thus, pre-flight fast duration is an important determinant of the fuels used inflight. (Funding: United States-Israel Binational Science Foundation).With: Lenny Gannes, Princeton University; Kent Hatch, Ben-Gurion University

Nectarivorous birds are represented by three major radiations: honeyeaters and sunbirds inthe Old World, and hummingbirds in the New. Costa’s hummingbirds and New Hollandhoneyeaters have unusually low protein requirements that have been related to the species’low-protein, high-sugar diets. Therefore, we hypothesised that orange-tufted sunbirds(Nectarinia osea) would likewise have low maintenance protein requirements and low ratesof endogenous nitrogen loss. To test this hypothesis, we measured nitrogen balance, totalendogenous nitrogen loss and body mass changes in captive birds, using insects as a proteinsource. In addition we made separate estimates of endogenous urinary and faecal nitrogenfor orange-tufted sunbirds. Nitrogen balance was less than one half of that predicted forbirds of the same mass, while total endogenous nitrogen loss is less than one third of theallometrically predicted value. Thus orange-tufted sunbirds follow the same pattern of lowprotein requirements found in hummingbirds and honeyeaters. Metabolic faecal nitrogenand endogenous urinary nitrogen of sunbirds were similar to those found for nectarivorous

desertecology 26

Test for physiological

limitation to nutrient

assimilation in a

long-distance passerine

migrant at a springtime

stopover site

Pinshow

Plasticity of

developmental

hierarchies in plants

Novoplansky

marsupials which have the lowest measured values for mammals. Low metabolic faecalnitrogen is attributable to a fibreless easily digestible liquid diet, while low endogenousurinary nitrogen probably results from efficient protein use. (Funding: Israel Science Foundation).With: Lizanne Roxburgh, Ben-Gurion University

During northward migration blackcaps arrive at stopover sites in Israel's Negev Desert withreduced mass of organs that are important in food digestion and assimilation. Blackcaps thatstay to refuel (largely on fruits) do not gain mass rapidly until after 3 days at the stopoversite. We hypothesized that 1) it may take several days to rebuild these reduced organs, 2)during this recovery interval high feeding rates might not be possible, and 3) this could be thebasis for the absence of immediate body mass gain in blackcaps at stopover sites. To testpredictions from this hypothesis we used an established fasting protocol to create a group ofblackcaps with reduced intestinal and liver mass, compared with ad libitum-fed controls.Migrants were captured and caged in the laboratory where they were habituated to a fruitmash diet for 8 days. One experimental group was then fasted two days, one was fed at arestricted level (one-third ad libitum food intake) for four days, and one group was held as adlibitum-fed controls. The fasted and restricted birds were then allowed to feed again adlibitum. Birds that were experimentally fasted progressively increased their daily assimilationrate and achieved the highest rate (one-third higher than controls) 3 days after the end oftheir fast. Birds that were restricted achieved high rates immediately once ad libitum foodwas provided. Increased assimilation rate was achieved via hyperphagia and not increasedassimilation efficiency. The response of the fasted birds supports the hypothesis that theremay be physiological constraints to the rate of refueling during migratory stopover. (Funding:US-Israel Binational Science Foundation; Fulbright Foundation).With: W.H. Karasov, University of Wisconsin, Madison

Behavioral Ecology and Life Histories

Organisms apply various mechanisms to cope with temporal and spatial changes in resourceabundance. They may, on the one hand, adjust their foraging strategies, i.e., behavior, and onthe other hand, they may modify their demographic strategies, namely, aspects of growth,reproduction, and seed dispersal. In deserts, environmental variation may be substantial andresources meager. Mitrani researchers examine the growth ‘decisions’ of plants underdifferent environmental regimes; the ways that insects and spiders make foraging decisionsand the life-history consequences of these decisions; and how foraging behavior can be usedto explain the interactions among species in desert ecosystems.

Allocation of resources to newly developing organs depends on the actual availability oflimited resources and the probability that these organs will successfully complete their lifecycle. A central question is, what are the environmental factors and the internal controls thatgovern the hierarchies and sizes of newly developing organs.Many plant organs are comprised of smaller functional units. For example, first-orderbranches would be functionally meaningless without their photosynthetic leaves. Suchhierarchical construction can be readily found in both the vegetative and the reproductivestructures of most plants. While allocation to relatively small organs allows swiftmaterialization and low risk of invested resources, the development of relatively large organsmay offer greater efficiency of resource use. The size of the developing organs is thusexpected to represent an inherent trade-off between efficiency and risk in resourceutilization. Accordingly, it is expected that the determination of the hierarchy and the size ofany given organ would not only depend on resource availability and the vigor of the plant butalso on the plant’s evolutionary background (e.g. general probability of catastrophes), and oninformation concerning its specific environment such as the time left to the end of theseason, and the expected future availability of limiting resources.With T. Sachs, The Hebrew University of Jerusalem; G. Jelschke, Jena University, Germany.

In the ecological growth facility,Mitrani researchers investigatethe growth ‘decisions’ of plantsunder different environmental

regimes.

desertecology 27

Genetic variability in

core and peripheral

plant populations:

relevance to drought

survival

Novoplansky, Safriel

Effects of resource

pulsing on individual

performance and

competitive hierarchies

in plants

Novoplansky

Root-root and

root-object

interactions: close

encounters of the second

and the third kinds

Novoplansky

The genetic variability of drought resistance was examined in plant populations near thecenter (core) and at the periphery of their distributions. Clover (Trifolium purpureum) andcooksfoot (Dactylis glomerata) were collected in the field from three core and four peripheralpopulations each. The specimens were grown in the greenhouse under high or low wateravailability throughout the growth season. While no consistent differences in the levels ofgenetic variability were observed in core and peripheral populations, plants from sites withinthe same regions varied considerably in almost all cases. This may mean that the populationsstudied may each represent a unique genetic background. We expect to examine the geneticvariations of populations in northern temperate climates and those in actual desertenvironments, and to compare these with populations of semiarid species examined here. With: A. Cahaner, Hebrew University of Jerusalem.

Although the question of whether competition intensity increases or is unchanging alongproductivity gradients has been highly controversial for a number of years, empirical resultsbearing on this question are quite variable and no consistent answer has yet emerged. Wesuggest that explicit consideration of resource dynamics within and between productivitylevels could clarify both existing theoretical predictions and the experimental evidence usedto test these predictions. When soil resources are temporally variable, plants will experiencetwo distinct phases of resource availability: relatively short pulse periods when resources arehigh and most growth and resource accumulation occurs and longer interpulse periods whenresources are more restricted and most mortality due to resource deficits takes place. Wesuggest that competition for limited resources takes place largely during pulse periods, whilestress tolerance largely determines survival during interpulse periods. As productivityincreases, the frequency of pulses (as well as or in place of their magnitude) often increasesand the duration of interpulse periods decreases. While competitive effects on growthshould occur during pulses at both high and low productivity, we suggest that competitionfor soil resources is unimportant in determining individual survival during interpulseintervals. For the longer interpulse intervals at lower productivity, the lack of competitiveinfluence on survival should further extend to lack of effects on population persistence. Thishypothesis predicts that relative competitive effects on growth should be similar at high andlow productivity, while competitive effects on survival and on population abundance andcommunity structure should increase with increasing productivity. Further, becausegradients in productivity due to water are more likely to fit the assumptions of thishypothesis than are gradients due to nutrients, we also predict that competition intensity ismore likely to increase along water productivity gradients than along nutrient productivitygradients. With: D. Goldberg, University of Michigan; A. Sher, BIDR

This study is aimed at studying the hypothesis that root communication plays a major role indetermining the directional responses and spatial distribution of roots. The foci of the studyare the directional responses of roots when encountering other (self or non-self) roots orinanimate objects. An experimental system was developed in which plants with two identicalroots are grown so each one of their roots is confronted with self roots on one side andwith non-self roots on the other side or when confronted by various physical obstacles.Preliminary results have shown that the roots of peas and beans are capable of avoidingnearby physical obstacles and prefer to branch towards neighboring non-self roots. Otherexperiments test the hypotheses that a) roots are capable of perceiving and avoidinginanimate objects by responding to self-inhibition substance(s) that are secreted by the rootsand are accumulated near physical obstacles; b) Plants use self/non-self recognition tominimize self and maximize non-self competitive interactions. The proposed study isexpected to contribute to the understanding of the unexplored complexity of root-root androot-obstacle interactions and to shed light on their population and community-levelimplications. With: M. Gersani, Ben-Gurion University

desertecology 28

Complex interactions

among spider predators

and spider prey

Lubin

Foraging Games Between

Owls And Gerbils:

Temporal Dynamics Of

Resource Depletion And

Apprehension In Gerbils

Kotler

Populations and Communities

The interactions between desert herbivores and vegetation or between animal predatorsand their prey are complex. An improved understanding of arid environments and attemptsto ensure their preservation require detailed investigations of population structures anddynamics as well as the interactions among indigenous species in desert communities. OneMitrani group investigates how vegetation structure and predation determine the speciescomposition of darkling beetles; a second collaboration studies complex interactions amongspider species; a third group probes the structure of desert rodent communities.

In the desert, complex interactions may exist between predators and their prey. Spiders mayaccount for nearly half the biomass of arthropod populations in deserts. The abundance offive species of spiders living in the Negev desert was investigated. Two of them (Poecilochroasenilis and Thyene sp.) are predators of one or more of the other three species (Mogrus sp.,Stegodyphus lineatus and Latrodectus revivensis). We found that Poecilochroa senilis attackspredominantly Mogrus, but will accept Stegodyphus, an alternative prey that is also attackedby Thyene. Predation pressure on Mogrus, the more vulnerable species, is reduced by itsseasonal migration into a different habitat. In other interactions, in winter, Poecilochroaspiders readily prey on Latrodectus spiderlings inside their cocoons. However, in summer,adult Latrodectus may trap and attack P. senilis. (Funding: Israel Science Foundation). With: M. Whitehouse, University of Queensland, Brisbane, Australia

Predator-prey interactions often constitute a foraging game in which prey individuals managerisk from predators and predator individuals manage fear in their prey. A tool of riskmanagement available to clever prey includes apprehension, the redirection of attentionfrom foraging to predator detection. One such foraging game occurs between gerbils andowls on the sand dunes of the Negev desert. Here, interacting species of gerbils compete forpatches of seeds that are renewed daily by afternoon winds. In such a situation, gerbils areexpected to deplete resource patches over the course of the night, owls are expected tohunt when gerbil activity is highest, and gerbils are expected to be most apprehensive whenowls are most active and most lethal. We tested these predictions for gerbils in two fieldexperiments using seed trays to measure patch depletion and apprehension over the courseof the night, between the bush and open microhabitats, and at four moon phases (new, halfwaxing, full, and half waning). The gerbils depleted seed resources gradually during thecourse of the night. Gerbils depleted seed resources more quickly in the bush microhabitatthan the open, and more quickly at new moon than at other moon phases. Moon phaseinteracted with timing of activity. Gerbil activity at new moon was high throughout most ofthe night, but decreased towards dawn. In contrast, activity at full moon was generally low,but increased towards dawn. The two gerbil species, Gerbillus andersoni allenbyi and G.pyramidum, partitioned the night, with G. pyramidum visiting resource patches earlier in thenight and encountering a richer, but more risky environment, and G. a. allenbyi foraging laterin an environment characterized by fewer seed resources, but lower risk. The same patternextended over moon phases, with G. pyramidum foraging relatively more at full and waninghalf moon. This resulted in the most extreme temporal partitioning occurring at new andwaxing half moon. Apprehension by gerbils was highest early in the night when seedresources were highest and gerbil activity most intense. Also, apprehension was higher at fullmoon than new moon when predators were most lethal. Finally, apprehension was higher inthe open microhabitat early in the night, but this difference disappeared as resourcesdepleted during the night, suggesting the role of owl attacks early on, but perhaps relativelymore attention directed towards snakes towards dawn. Apprehension thus appears to berelated to the forager’s activity, as well as conditions that affect predator lethality andencounter rates with predators. The environmental conditions, resource depletion, thedecisions of the gerbils regarding level of activity, location of activity, and level ofapprehension, and the decisions of the predators regarding level and timing of activity are alltied up in the foraging game. This game affects three trophic levels, including the effect of the

In the aviary, researchersinvestigate predator behavior of

barn owls (Tyto alba.)

desertecology 29

Examining parental

investment in themselves

and their chicks:

differential food

allocation by parent

sunbirds

Pinshow

Community structure of

desert rodents

Abramsky

gerbils on the availability and distribution of seeds, the competitive interaction between thetwo gerbil species, and the predator-prey interaction between gerbils and owls. (Funding:U.S.-Israel Binational Science Foundation) With: J. S. Brown, University of Illinois at Chicago; S. R. X. Dall, Cambridge University; S. Gresser, University ofSydney; D. Ganey, Emporia State University; A Bouskila, BIDR

Provisioning of young in the nest by parent birds is a classic example of central-place foraging;it is also a time when crucial life history decisions are made. Food delivery has fitness benefitsthrough its effects on nestling survival and growth. It also has survival costs in terms of thetime and energy spent by the parents while provisioning and their increased exposure topredators. Previous theoretical and empirical studies of parental allocation decisions havegenerally dealt with sharing by parent birds of standard food items between themselves andtheir chicks. However, food types may differ in suitability for transport back to the nestand/or in nutrient content. This may have consequences for both foraging and allocationdecisions made by parent birds. Specifically, the availability of energetically profitable fooditems that the parent itself eats should influence the total rate at which it can deliver otherfood items to the nest. We found that while parent orange-tufted sunbirds (Nectarinia osea)consume flower nectar and arthropod prey, they supply their chicks with exclusivelyarthropod prey. Thus, manipulation of the nectar source can be used to test hypothesesregarding strategies of parental investment, foraging, and the trade-off between self-feedingand provisioning. We used orange-tufted sunbirds to test the hypothesis that parents changethe total amount of food delivered to their young according to the energy content of thefood they consume. Pairs with two or three chicks were provided with feeders containinglow, medium or high concentration sugar solutions. As sugar concentration increased, 1)both parents (especially the females) delivered more arthropods to the nest; 2) malesincreased their nest-guarding effort; and 3) inter-brood interval decreased. Nestling foodintake, growth and survival all increased with increasing sugar concentration and withdecreasing brood size. We concluded that increased energy intake by parent sunbirds affordsthem the extra time and/or energy to invest more in their young, with consequent positiveeffects on their reproductive output. (Funding: Mitrani Center for Desert Ecology).With: Shai Markman, BIDR; John Wright, University of Wales, Bangor

Using the theory of density-dependent habitat selection, we have spent almost a decadestudying the interactions of two gerbils, Gerbillus allenbyi and G. pyramidum, in the sandyhabitats of the Negev desert. We have successfully measured the gerbils’ interspecific andvictim isoclines, the latter by using trained owls. We also determined the relativecontribution of predation and competition to fixing population densities. Presently, theenergetic costs of several biotic interactions are being measured, including competitionwithin and between gerbil species, risks of predation, and habitat selection. We are alsoinvestigating the long-term influence of risk of predation on rodent population dynamics andinteractions, as well as its indirect effects on other seed-eating organisms and on annualplants. (Funding: US-Israel Binational Science Foundation; Israel Science Foundation).With: M. Rosenzweig, O. Ovadia, G. Ben-Natan, and A. Bar, Ben-Gurion University

Female black widow spider(Latrodectus revivensis) with her

egg sac. These spiders feed on awide range of surface-dwelling

arthropods, including scorpionsand solifuges many times their

size.

desertecology 30

Conservation priorities

based on genetic

diversity across an

ecological gradient

Safriel

Assessing grazing impact

by remote sensing in

hyper-arid

environments

Saltz

Conservation Ecology

The spreading desertification in many areas of the world, including the south of Israel, hasbeen well documented. This phenomenon, along with man-induced disturbances, can lead tothe extinction of populations and to the reduction of genetic variation in the populations thatremain. Mitrani Department researchers investigate genetic and phenotypic variation inplants, the conservation as well as the reintroduction of endangered mammalian species, andthe conservation and restoration of acacia savannas and of the Carmel forest ecosystem.

It is hypothesized that the most genetically diverse populations within a species’ range occurwithin an area of transition between ecosystems where a sharp environmental gradientexists – the ecotone. Many of the Israeli animal and plant species occur along a steepeco-geographical gradient extending from mesic Mediterranean zones in the north to steppeand desert regions in the south. To test the hypothesis, the genetic variability as expressedby allozyme diversity of one such species, the Chukar Partridge, Alectoris chukar was sampled.Based on 32 allozyme loci, the genetic diversity of chukars increased significantly along thegradient from populations in Mediterranean regions to those at the ecotone in the northernNegev desert. It may be therefore recommended that for protecting the highestwithin-species diversities, higher conservation priority be assigned to theMediterranean-Negev ecotone area. With: S. Kark, P. Alkon and E. Randi

Assessing vegetation status via remote sensing techniques using various vegetation indiceshas been successfully applied to semi-arid and arid environments. We tested the feasibility ofapplying such techniques for assessing grazing impact in hyper-arid environments with a highvariance in soil type over space. An anticlinal erosional cirque called Makhtesh Ramon in theNegev desert, Israel, was selected for the study. The cirque is typified by low rainfall (40-90mm per year), a variety of soil substrates and is subject to grazing by a herd of Asiatic wildasses (Equus hemionus) reintroduced into the cirque between 1984 and 1987. As a control,we used an ungrazed dry riverbed south of the cirque that runs parallel to the riverbeddraining the cirque. We used five common vegetation indices derived from Landsat 5 satelliteThematic Mapper (TM). Four images were used, representing dry and wet seasons in above-and below-average rainfall years (1995 and 1987, respectively). To test whether we candetect changes in plant community structure via satellite data we correlated vegetationindices from the TM to ground measurements made along the altitudinal gradient of thecirque. To test whether differences in plant cover could be detected, we correlated thevegetation indices with ground measurements of cover in and out of the cirque (grazed andungrazed areas). Although ground measurements showed that community structure changedfollowing grazing with altitudinal gradient and ground cover 30% lower inside the cirque thanoutside the cirque, none of the five vegetation indices correlated with the groundmeasurements. Transformed Soil Adjusted Vegetation Index (TSAVI) and NormalizedDifference Vegetation Index (NDVI) produced the best results. We hypothesize that the lowvegetation cover that typifies hyper-arid environments increases the noise to signal ratio.Thus, a 30% decline in vegetation cover in this case is only an absolute decline of 4% from15.8 to 11.2%. Because TM is sensitive to absolute cover rather than the relative differences,it is difficult to demonstrate differences among TM images. Using ANOVA to test the effectof season and grazing status on TSAVI and NDVI, we found a significant interaction betweenseason and grazing status in 1995 with indices declining more from wet to dry season insidethe cirque than outside the cirque. No such pattern was found in 1987. These data suggestthat satellite imagery may detect changes in plant cover over time but cannot serve as adirect index of plant cover in hyper-arid conditions.

desertecology 31

Large mammalian

herbivores and the

conservation of acacia

stands in arid regions of

the Middle East

Ward

Desert ecosystems

Shachak

High mortality, poor germination, and the poor survival of young native acacia trees in manyMiddle Eastern regions may result in the loss of some five other plant species, which dependon the acacias for nitrogen and shade. We studied the effects of large mammalian herbivoreson the establishment of young Acacia raddiana and A. tortilis in the Arava Valley between theRed Sea and the Dead Sea, Israel. Seed accumulation under trees was high when largemammalian herbivores such as gazelles and camels were excluded, and direct observationsconfirmed that these mammals were the main seed dispersers of these Acacia species. Insectseed predators (bruchid beetles) damage more than 95% of seeds not consumed byungulates. Moreover, seed germination was facilitated by passage through the mammalianungulate gut. Under present conditions, several years of high rainfall are necessary for thesuccessful establishment of young trees. Under severe browsing pressure, growth of juveniletrees was delayed and smaller size trees were over-represented. There was no evidence,however, of negative effects of this browsing on the long-term demography of acacia trees.We conclude that large mammalian herbivores are essential components of arid acaciasavannas, and that wild domestic ungulates must be included in future conservationprograms. (Funding: German Ministry of Environmental Affairs, Israel Ministry of Science, andKeren Kayemet L’Yisrael (JNF).

Ecosystem Studies

Ecosystem studies address the complex of a community and its environment functioning asa single ecological unit. Dealing with problems on that very inclusive ecosystem approach,Mitrani scientists are studying the interactions between organisms at several levels of thefood chain, providing insights into the dynamic processes that determine the structure andfunction of desert ecosystems, as well as the impact of man on these ecosystems.

Various aspects of the interactions of animal and plant communities with their environmentsare under investigation. These include studies of: organisms acting as ecosystem engineers inthe Negev (with C. Jones, Institute of Ecosystem Studies [IES]); the dynamics of patchyvegetation in semiarid systems (with G. Lovett, IES); the effects of grazing on patchiness,resources, and organisms in a semiarid landscape (with A. Perevelotsky, Volcani Institute,Israel); the structure and function of sink-limited systems (with S. Pickett and P. Groffman,IES; and A. Karnieli, B. Boeken, and E. Zaady, BIDR); human-induced changes of therelationship among patchiness, resource flow, and biological productivity and diversity (withS. Pickett, IES); the role of invertebrates in ecosystem functioning in arid lands (with A.Wilby, BIDR); and, seed flow in a semiarid landscape (with H. Kugel, Hebrew University ofJerusalem, and B. Boeken, BIDR).

desertecology 32

The Ramon Science CenterProf. David Ward, Head

The Ramon Science Center conducts long-term research on the ecology and geology of theMakhtesh Ramon and surrounding environment in the central Negev desert. The center issituated in the town of Mizpe Ramon, about 35 kilometers south of the Jacob BlausteinInstitute for Desert Research in Sede-Boqer and is affiliated with the Mitrani Department ofDesert Ecology.Makhtesh Ramon is a large erosion crater some 40 kilometers long and about 8 kilometerswide, surrounded by 400 meter-high natural walls. Initially established as a geological parkbecause of its remarkable diversity of geological structures and habitats, this crater nowforms the central part of Israel’s largest nature reserve – the Negev Mountains NationalPark. Makhtesh Ramon is home to a wide variety of desert animals and plants, some of whichare found nowhere else. Of particular ecological interest is the fact that the crater forms anatural boundary between two major biogeographic zones, the steppe (Irano-Turanian) andthe true (Sahara-Arabian) desert. As such, the crater is an extraordinary natural laboratoryfor the study of ecological interactions of the two floras and faunas. The academic staff of the Ramon Science Center includes three geologists and threeecologists.

Academic STaffAvni, YoavKrasnov, Boris Plakht, Josef Sheinkman, VladimirShenbrot, Georgy Ward, David

Phone: 972-8-658-8764 • Fax: 972-8-658-6369

Adjunct Researchers

Prof. Emanuel Mazor, Weizmann Institute of ScienceDr. David Saltz, BIDR

Satellite photo of MakhteshRamon, a large erosion crater inthe Negev highlands. Forming a

natural boundary between theIrano-Turanian steppe region in

the north-east and theSahara-Arabian desert which lies

to the south, Makhtesh Ramonpresents researchers with unusual

opportunities for geological andecological investigations.

desertecology 33

Mapping of Quaternary

deposits in Makhtesh

Hatira and Makhtesh

Hazera

Plakht

Morpho– and

chronostratigraphy of

the Quaternary of the

middle Nahal Zin

Plakht, Sheinkman

estimating

erosion-accumulative

activity in the Central

Negev

Sheinkman

Ongoing destruction

process of loess land

reducing pastoral and

agriculture uses: Negev

Highlands

Avni, Plakht, Ward

Synoptic patterns, storm

tracks and distribution

of rainfall causing the

extreme floods in the

Negev Mountains

Avni, Ward

Research Activities

Geology

This work represents an attempt to construct Quaternary maps in a genetic-chronologicalorder. Two maps depicting Quaternary geology of Makhtesh Hazera and Makhtesh Hatira areprepared at the scale of 1:50,000. The major mapping unit is by genetic type of sediment. Eachgenetic type is further subdivided according to age. Quaternary mapping of Makhtesh Hazeraand Makhtesh Hatira is based on: (1) development of a morphostratigraphic scheme anddefinition of genetic types of sediments (including construction of geological-geomorphologicalcross- sections in different portions of valleys, construction of longitudinal profiles of riverbeds and terraces and detailed study of pediments as integral components of the landformsystem) and complex analysis of alluvium and loess as a tool for stratigraphic correlation(lithological analysis, the study of paleosoils and absolute dating of terrace alluvium).

As a key to the paleogeographic resconstruction of the Negev, we are investigating andmapping, at a scale of 1:50,000, the Quaternary units in the middle reaches of Nahal Zin.This allows us to express the spatial distribution of Quaternary sediments and to determinethe relative time-scale of regional Quaternary history. The study includesmorphostratigraphy of the river valley, study of the alluvium composition and sampling forabsolute age determination.

Determining the connections between landforms and composing rocks in theMakhtesh/Nahal Zin/Dead Sea geomorphosystem allows us to estimateerosion-accumulation in the Central Negev. We studied the staircases of terracescomposing the Nahal Zin and Nahal Hatira valley and elaborated the morphostratigraphicscheme. Our investigation shows that the -130-m level of the maximum ingression of DeadSea in the Nahal Zin canyon compares to the –180-m level in the formerly printed materials.The complex facial composition of ancient lake and fluvial sediments were determined, anddata collected on the first absolute ages of the sediments.

In southern Israel, gully erosion creating badland topography is a well-known phenomenondeveloped within loess soils and fine alluvial sediments. This phenomenon becomes critical inthe Negev Highlands where potential agricultural fields are limited to narrow valleys. During the last 15 years, we monitored and studied the mechanism and the rate of gullymigration in several locations in the region south of Beer-Sheva. and found that thedevelopment of a deep and narrow gully concentrates the runoff and restricts the irrigationeffect of the floods from the whole width of the valley. As a result, a reduction of about 80%of the floral biomass was observed and the agriculture potential was severely damaged.These parameters indicate ongoing aridization of the area that is proceeding at a rate ofseveral meters per year for each gully.Preliminary results relate the ongoing destruction of the loess cover of the Negev Highlandvalleys to a dynamic change in the rock/soil ratio during the Holocene. With: A. Yair, Hebrew University of Jerusalem

The purpose of this three-year project is to study the synoptic patterns and the storm tracksthat cause extreme flooding in the Negev highlands region. Special concern will be given tothe storms and floods caused by the "Red Sea low pressure" that is responsible for the majorflood events known in the region. One of the aims of the research is to evaluate and analyzethe floods and synoptic data collected in the last 40 years in the region. Ongoing monitoringof present and future events will be done during the course of the research project.With: Y. Enzel and R. Cahana, Hebrew University of Jerusalem

desertecology 34

Urban ecology of a

settlement in close

proximity to a

nature reserve

Ward, Mazor, Plakht,

Krasnov, Avni, Shenbrot

Monitoring of the biota

of Ramon park Nature

Reserve using

tenebrionid beetles

Krasnov

Ecological and

physiological

parameters of Gerbillus

gerbillus from isolated

population

Krasnov, Shenbrot

Respiratory gas exchange

and ventilatory

characteristics in fleas

Xenopsylla conformis

and Xenopsylla ramesis

Krasnov

Ecology

The purpose of this complex study of geology, geomorphology, botany and zoology is torepresent the ecology of the town of Mitzpe Ramon and its surroundings, the MakhteshRamon Nature Reserve, in order to determine rational methods for land use andconservation of the desert environment both inside the town and in the adjacent naturereserve. Particular attention is being devoted to the influence of the marble quarries on theenvironment of the town. We suggest alternatives, which do not disturb the naturalenvironment, to the present-day quarries.

One of the principal purposes of nature reserves is to estimate what degree of protection isneeded to insure the required level of nature conservation, and to evaluate the results ofmanagement practice. The solution of this problem includes developing the principles of themonitoring process, which are urgently needed for nature reserves and for particularlysensitive nature zones as, for example, Makhtesh Ramon. Recording the changes inabundance, diversity and biology of plants and animals is vital for decision-making inconservation. The monitoring of living organisms is becoming accepted as a moreinformative method than that of monitoring physical or chemical variables when assessingthe effect of environmental change on ecosystems. The principal objective of the monitoringis not to find solutions to methods of management, but to derive information on the biotastate and the extent of change in it. It is then up to the managers and biologists to determinethe causes of change and thence determine how to prevent changes from getting worse andhow to reverse the situation. Since it is impractical and impossible to monitor allcomponents of the reserve biota, it is necessary to select just a few components, which willserve as bioindicators for the state of nature in the reserve. We elaborated monitoringprotocol using tenebrionid beetles as indicators of the biota state and continue to performroutine monitoring of this taxon in Makhtesh Ramon and the vicinity.

Populations of rodents isolated on islands often show systematic differences in theirdemography, reproduction, behavior, and morphology when compared to mainlandpopulations. These differences, termed "the island syndrome", include many distinctivecharacteristics. In Israel, Gerbillus gerbillus (Rodentia:Gerbillidae) represents a pattern ofdistribution which is similar to the mainland-island pattern. It occurs in two main areas, namelyin Holot Agur, Holot Shunra and Holot Nachal Secher in the northwest Negev and in HolotSamar in the Arava Valley. In addition, G. gerbillus inhabits small isolated sand dunes in theeastern part of Makhtesh Ramon. This pattern of distribution provides a good opportunity forstudying the island syndrome of the isolated population of this rodent. Our research dealswith the comparative aspects of the ecology, physiology, behavior and genetics of differentpopulations of G. gerbillus. We compare G. gerbillus from an isolated population with twomainland populations. The aim of the research is to evaluate genetic, physiological, behavioraland ecological specificity of individuals in the isolated population of G. gerbillus and to reveal thepossible connections among the "mainland" and "island" populations, the history of the speciesdistribution in the region, and the degree of the isolation of Makhtesh Ramon population.With: I. Choshniak and P. Sinai, Tel Aviv University

Measurements of respiratory gas exchange on fleas at similar stages of development at 25oCallowed us to determine and developm a set of standardized parameters for quantifying bothmetabolic and ventilation characteristics of the prepupa and pupal stages as well as the newlyemerged adult and feeding adult stages. Flea-respiratory gas exchange involved measurementof CO2 emission using a high resolution flow-through respirometry system. Fleas wereinitially measured individually but later in groups to minimize error associated withinstrument drift. When measured in groups, fleas soon settled and remained quiet in therespirometer chamber. No significant differences were found between individual and grouprecordings of fleas. Cocoon stages of known age were measured in the intact cocoons. Afterthe recording, cocoons were dissected and the developmental stages inside identified and

desertecology 35

Characterization of

whole body permeability

in flea Xenopsylla

conformis

Krasnov

Flea fauna of

Southern Israel

Krasnov, Shenbrot

Rodent and snail

biodiversity in different

habitats of the southern

Israel

Shenbrot, Krasnov

Habitat dependence of

the architecture and

microclimate of

Meriones crassus

burrows

Shenbrot, Krasnov

weighed. Vco2 has been measured for all developmental stages of X. conformis and for thenewly emerged adults of X. ramensis. Continuous ventilation was found in adult and preimagostages. In X. conformis, the life cycle stage with the highest energy requirements is the feedingadults. High metabolic rate in this hematophagus stage is probably associated withblood-meal digestion and in females, oogenesis and ovipostion. Lowest energy requirementsare characteristic of the nonfeeding off-host cocoon stages: prepupa, pupa and premergedadults. Such low metabolic rates are expected in the cocoon stages as they form the mainresting stage for many flea species. Mass specific metabolic rate of the unfed stages of X.ramensis did not differ significantly from those of X. conformis. Smaller size of X. ramensis incomparison to X. conformis resulted in higher CO2 emission rates per individual flea.With: I, Khokhlova, Desert Animal Adaptations and Husbandr;, L. Fielden, Truman University, USA

Whole-body permeability measurements at 25oC and >5% RH estimate water loss viatrans-cuticular and respiratory avenues. These measurements determine "leakiness" of thetwo flea species as well as susceptibility of the different life cycle stages to dehydration. Datahave been collected for newly emerged adults of X. conformis. Fleas were placed in groups (n≥10) in perforated microcentrifuge tubes at 25oC in a drierite dessicator (>.5% RH). Massloss measurements were made at 12 h intervals and water loss rates estimated. Water lossrates are high and adults show little tolerance to dessicating conditions. Approximately 50%of the fleas were dead after 24 hrs and no fleas survived more than three days.With: L. Fielden, Truman University, USA

We investigated 14 rodent species from 18 localities yielding fourteen species of fleas.Nosopsyllus i. theodori is reported from Gerbillus gerbillus, Gerbillus henleyi, and Mus musculus inIsrael for the first time. Additional records of Coptopsylla africana in Israel substantiate thepresence of this species in Israel.With: M. Hastriter, Bringham Young University, USA S. Medvedev, Sociological Institute, St. Petersburg, Russia

The project is devoted to development of an Intelligent Biodiversity Information System forthe central Negev desert. The system will allow decision makers to identify patterns ofbiodiversity at spatial scales ranging from local sites of 100x100 m to the entire CentralNegev, and to evaluate local and regional losses in biodiversity expected from potentialfuture scenarios of habitat destruction and development programs. The system underdevelopment is based on empirically-derived species response models that predictprobabilities of species occurrences at a site from information on climatological and edaphicfactors. Data for model calibration are being obtained from an extensive sampling projectcovering the main climatological and edaphic gradients of the central Negev (the faunal dataon rodents and snails) and maps already available in a digital form (rainfall, temperature,topography, geology, soils).With: R. Kadmon and Y. Heller, Hebrew University of Jerusalem

The jird Meriones crassus, which occupies several habitats in the central Negev, demonstrateschanges in its flea composition (Xenopsylla conformis versus Xenopsylla ramesis) amonghabitats along the rainfall gradient. The working hypothesis is that this replacement iscorrelated with host-habitat factors, specifically temperature and humidity. To check thishypothesis, the structure and microclimate (temperature and humidity) of jird burrows werecompared in two different habitats. Significant between-habitat differences were found in thegeneral length of burrow tunnels, the number of burrow openings and in the burrow airhumidity.

desertecology 36

population and

community dynamics of

Central Negev rodents

Shenbrot

Genetic diversity and

water stress in isolated

Negev desert populations

of Acacia raddiana

Ward

Water stress in

Acacia raddiana

Ward

Soil factors as

indicators of

desertification in an

agro-ecosystem in the

northern Negev

Ward, Avni

Since 1993 we have been monitoring the central Negev rodent populations on 24 samplegrids established in Makhtesh Ramon and its vicinity. The aim of this long-term program is toestimate the influence of environmental fluctuations on populations of individual species andon the whole community in a system of habitat mosaic within a complex landscape.

There is widespread concern over mortality of native Acacia trees in the Negev desert,Israel. Mortality varies widely, and may reach as high as 61% in populations of adult trees. Thethreat of extinction is becoming evident in these Acacia spp. due to high mortality and rarerecruitment of seedlings. It is hypothesized that diminished genetic diversity has resultedfrom these populations’ decline. The present study focused on Acacia raddiana because it isthe most widespread species among the three native Acacias. We selected five sites with thehighest mortality and three sites with the lowest mortality out of 75 sites surveyed. RandomAmplified Polymorphic DNA (RAPD) markers were used to assess the relationships andgenetic diversity among these populations. We investigated whether mortality is related tocurrent water stress in these populations using a Scholander pressure chamber. There isconsiderable genetic variability among populations and a high degree of polymorphism withinpopulations. Low genetic polymorphism is not associated with high mortality populations.We found that high mortality populations have significantly more negative water potentialsthan low mortality populations. There was a negative correlation between water stress andgenetic polymorphism, indicating that genetic polymorphism may be important inwithstanding environmental stress. With: M. Shtresha, Ben-Gurion University

Many populations of native Acacia raddiana trees in the Negev desert suffer from highmortality. Road-building techniques that cut off water to trees in downstream populationsand pumping of aquifers for agriculture have been mooted as causes of this mortality. Westudied the water relations of nine isolated populations of these trees using a Scholanderpressure chamber and stable carbon isotopes in order to determine whether current waterstress could be the cause of this mortality. We found that high mortality populations havesignificantly more negative water potentials, lower relative water contents and lower cellwater volumes at full turgor than low mortality populations. These results show thatmortality is correlated with current inter-population differences in water stress. However,we found no significant difference in water potential between trees upstream anddownstream of roads, indicating that this is not the current cause of water stress.Furthermore, greater water stress in trees after a dry winter than in the previous summerindicates that these trees are largely drawing on surface floods for water and seldom useaquifer water. Thus, aquifer pumping is an unlikely cause of mortality. Hence, water stress islinked to mortality in these trees; our results indicate that irregular water stress (perhaps indrought years only) is the cause of this mortality.With: M. Shtresha, Ben-Gurion University

Flash floods during winter cause erosive activities in the basins and adjacent agricultural areasin the semi-arid parts of the Negev desert of Israel. This has led to the formation of waterfalls(gullies) that erode streams. Consequently, this has led to the loss of soil nutrients over time.Soil erosion in conjunction with human activities has greatly contributed to desertification inthis part of the Negev. We set out to examine the effects of soil erosion and agriculturalpractices in seventeen eroded sites in the northern Negev desert. Our presumption wasthat soil erosion and agricultural activities would reduce soil quality. In all the parametersinvestigated there were significant differences between sites. Areas above (uneroded) andbelow (eroded) gullies and distances (5, 10 and 20m) from waterfalls showed significantdifferences at all sites under investigation. Salinity was highest in the nature reserve sites andirrigated areas because of accumulation of bases resulting from reduced leaching andcontinuous supplies of heavy metals from brackish water used in the irrigation system,respectively. Organic carbon increased along a moisture gradient, being lowest in areasreceiving 200 mm and highest where rainfall is over 300 mm per year. Nature reserves had

desertecology 37

The population of the

Pistacia Atlantica as a

tourism resource in the

Makhtesim region –

destruction and

conservation patterns

Avni

higher organic carbon than cultivated areas. Nitrogen showed significant differences bothbetween sites and eroded versus uneroded areas. Biomass of plants in a bioassay showed apositive correlation with the amount of organic carbon, an indicator of a reduction in soilquality. Water holding capacity was higher in nature reserve soils than in cultivated areas,whereas eroded sites contained bigger soil particles than uneroded ones.With T. Akuja

In the Negev Highlands, several hundreds of Pistacia atlantica trees are widely distributedalong the valleys, especially in the range of 700-1000 m.a.s.l. The present research analyzesthe population of the Pistacia atlantica in Nahal Loz, central Negev highlands, to determinethe following points: 1) the distribution of the young trees relative to the older ones in orderto evaluate the vitality of the population; 2) the distribution of the sex ratio in the population;3) the geomorphological characteristics of the tree locations; 4) the effect of erosion on thetree population – especially the relations between the young trees and the erosion featureslike gullies development; and 5) the rule of the erosion over the last hundreds of years basedon the position of old trees relative to the erosive features.The distribution of Pistaciaatlantica in Nahal Loz has been affected by erosion in the last few years, putting the trees indanger of extinction. The recruitment potential of the trees however still seems toovercome this problem. There are enough young trees for replacement, and the distributionof the sexes appears balanced enough.The next stage of the research will focus on analyzing the role of erosion on the destructionof the Pistacia population, and developing methods for conservation.

desertecology 38

The ibex (Capra ibex nubiana) hasbeen the focus of several

ecological studies.

Insects in a changing

desert environment: A

study of the biodiversity

and documentation of

the entomofauna of the

Arava valley

Yarom

Biodiversity of Tamarix

and associated insects in

natural and disturbed

habitats in Israel

Yarom

HAZEVA RESEARCH ANDDEVELOPMENT CENTER (HRDC)

Dr. Ilan Yarom, Scientific Director

The Hazeva Research and Development Center (HRDC) is located in the central Arava RiftValley, between the Dead Sea and Eilat. The Arava Rift Valley, home to some of the mostpristine habitats in Israel, offers singular opportunities for research. There is anextraordinary confluence of natural ecosystems in the area with a beautiful and fragilemixture of plants and animals originating from different biogeographical zones: African Acaciatrees, the Arabian babbler (an Asian song-bird), and the common wolf whose habitat extendsto Europe. Many species cannot be found elsewhere in Israel. The nearby Shezaf NatureReserve is about 9,500 acres and serves as a natural laboratory for scientific research. The Ministry of Science and the Central Arava Regional Council are the main sponsors ofHRDC and since 1996 HRDC has been academically affiliated with Ben-Gurion University ofthe Negev’s Jacob Blaustein Institute for Desert Research.The major areas of research at HRDC are: biodiversity, conservation of natural resources,ecological tourism, sustainable agriculture, and regional development. Researchers fromacademic institutions in Israel and around the world collaborate on research activities.HRDC’s 1999 budget was approximately $200,000. An additional $200,000 was securedfrom research grants in 1999.

Hazeva Research and Development Centerc/o Hazeva Field School, Mobile Post Office Ha’Arava 86815, IsraelPhone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: iyarom@bgumail.bgu.ac.il

Research StaffDr. Ilan Yarom, Entomologist and Scientific Director.Dr. Rivka Ofir, Cell biologist and molecular geneticist Dr. Vasiliy Kravchenko, Entomologist, Research fellowDr. Avner Anava, Zoologist; Postdoctoral FellowGideon Wasserberg, Ph.D. candidate (Ben-Gurion University)

Research Activities

Until now, there have been few studies on the insect fauna of the Arava. This is the firstcomprehensive multi-year effort aimed at understanding the biodiversity of the entomofaunaof the Arava Rift Valley. Special attention is given to finding potential pests and promisingnatural enemies that may serve as biological agents in future biological control or IPMstrategies employed in the agriculture fields of the region. Insects are collected by staffmembers and visiting entomologists throughout the year using various methods includingaerial collecting, Malaise traps, light traps and others. The material is preserved by regularmethods and identified by local taxonomists and colleagues around the world. Most of thematerial, including type specimens of the new species, will be deposited at the NationalCollection of Insects at the Department of Zoology, Tel Aviv University. With: V. Kravchenko, HRDC

This joint Israeli-German, three-year interdisciplinary project serves as a model for the studyof human impact on biodiversity. This unique ecosystem comprised of species of Tamarix andassociated insects is being studied in natural and disturbed habitats. Habitats in the Arava arealso being compared with those in the coastal plain and Dead Sea area. This is a pioneeringstudy of biodiversity changes at the ecosystem level for the entire Mediterranean basin. It willcontribute to knowledge of the biology and ecology of Tamarix -based ecosystems and to theunderstanding of the mutual relationships of Tamarix plants with their associated insects atall trophic levels.With: D. Gerling, A. Freidberg, A. Eshel, Tel Aviv University; C. Zebitz, University of Hohenheim, Stuttgart,Germany

desertecology

Ecology of fresh water

reservoirs in the Arava

region, limnological and

ecological effects in

reservoirs and

downstream

Yarom

impact of flash flood

interception on Arava

shallow groundwater

Yarom

development in the

Arava and its effect on

relationships between

host and vector of

coetaneous

leishmaniasis

Yarom

The fat-sand-rat

(Psammomys obesus) as a

potential new tourist

attraction for the

Arava

Anava

Phytochemicals in the

Arava plants: Screening

for their

pharmaceutical

potential

Ofir

39

A new system of water reservoirs was built in the Arava in recent years. The purpose of thereservoirs is to capture floodwater in the desert wadis for irrigation and to recharge theunderground water basin. The goal of this study is twofold: 1) to identify the dynamics of thelimnological processes of the captured water; 2) to identify the ecological changes caused bybuilding the reservoirs, both around the reservoirs and downstream. Preliminary resultsshow remarkable differences between the two reservoirs under investigation: Thedownstream reservoir (Iddan reservoir) is much more eutrophic than the upstreamreservoir (Zukim reservoir). We suspect that intensive agricultural fields located betweenthe two reservoirs, but absent upstream from the Zukim reservoir, contribute toaccumulation of nutrients in Iddan reservoir. We found out that there is a rapid microalgaegrowth in Iddan reservoir vs. macroalgae in Zukim reservoir. With: S. Gafny, Tel Aviv University

Our goals are to clarify the relationships between flash-flood water and shallow groundwater and to examine the impact of a massive environmental disturbance (catching floodwater) on the natural balance of the water system in the Arava. The study employsgeochemical and isotope characterization of shallow ground water near water reservoirs,their temporal and spatial changes, and developing a model for evaluating the relationshipsbetween floodwater, captured water, and ground water. With: A. Bein and A. Burg, Geological Survey of Israel

Coetaneous leishmaniasis ("Jericho rose lesion") is a common human disease in the Aravavalley. Although coetaneous leishmaniasis is not lethal, the lesion may leave a noticeable scar.It is caused by a parasite and transmitted from local rodents to humans by sand flies. Westudy the major environmental factors that affect the populations of the carrier rodent, suchas population dynamics and ecology, patterns of dispersal and activity, epidemiology of therodent population and the influence of human activity on the rodent populations and sandflies (the vector).With: G. Waserberg, Z. Abramsky, Ben-Gurion University; A. Warburg, Hebrew University, Jerusalem.

The fat-sand-rat is a diurnal rodent that lives in small colonies. The goal of this study is todevelop a new attraction for ecological tourism, much like the native Arabian babbler, whichis well known as a social bird and attracts students of all kinds from Israel and abroad. Theresearchers are working in two directions: 1) to accustom the gerbils to the presence ofhuman observers; 2) to study the behavior of the gerbils, their physiology, and otherinformation for preparing an ecotourism program.With: I. Yarom, HRDC; M. Kam, and A.A. Degen, Ben-Gurion University

The research focuses on four projects:1. Collecting desert plant extracts that will serve as a library of natural products forscreening phytochemicals for use against various biological causes of human diseases.2. High Throughput Screening (HTS) of phytochemicals for activating or repressing the"killing proteases" (Caspases) involved in programmed cell death (apoptosis). HTS of the first100 desert plant extracts resulted in the identification of 10 plants containing phytochemicalscapable of activating caspase-3 activity in cancer cells (leading to cytotoxicity accompanied byDNA Ladder).3. HTS of natural products against serotonin re-uptake: potential treatment for depressionin pre- and postmenopausal women. Serotonin plays a major role in depression at times ofchanging hormone levels in women. Phytochemicals will be screened for their effect on theuptake of serotonin by recombinant human serotonin transporter.4. HTS of Indian plant extracts for cytotoxic activity against cancer cells and for pro-apoptotic activity. Thirty extracts prepared from plants used by local Indian doctors asmedicine were screened for pro-apoptotic activity. Two plants contain compounds capableof activating caspase-3 and killing human cancer cells grown in vitro. Plants with functionalactivity may be considered for future cultivation as a potential new crop in the Arava.

desertecology 40

Microbial degradation

of polyethylene waste in

the Arava Valley

Ofir

Cooperative monitoring

for long-term

sustainable land use in

the Middle East

Zaady

The use of isolated bacteria that are able to use polyethylene as the sole carbon source isbeing tested in a pilot project in the Arava. The goal is to develop a biotechnological methodfor using these bacteria for degrading the large mound of polyethylene waste accumulatedfrom agricultural use of polyethylene. With: A. Sivan, Institutes for Applied Research, Ben-Gurion University

Desertification and RestorationEcology Research Center

Dr. Eli Zaady, Resident Scientist

The Jewish National Fund (JNF), motivated by the need for research to support its drylanddevelopment projects, established the Desertification and Restoration Ecology ResearchCenter jointly with the BIDR. The Center promotes interdisciplinary research into thecauses of desertification, develops means of preventing it, and methods for restoring alreadydesertified areas.

Research Activities

Desertification is a world-wide problem in arid lands that is made worse by populationgrowth, urban development, and inappropriate agricultural techniques. Implementing a landmanagement program based on sustainable land use techniques can prevent desertification.Sustainable land use relies on land quality indicators to identify problems and measuretrends. Research is needed to fully understand how land quality indicators change over longperiods under varying conditions. Sustainable land use is of particular importance in theMiddle East. Population and economic growth are straining the environment's ability tosupport human activity. These trends are particularly acute in the "fertile crescent" extendingfrom Egypt to Lebanon. The Middle East peace process recognized the importance of theenvironment in a stable peace by establishing a working group on the environment. Thecommonality of the problem presents an opportunity for regional scientists to collaborate inthe collection, exchange, and analysis of environmental data. The Cooperative MonitoringCenter (CMC), Sandia Laboratories, in association with the US National ScienceFoundation's International Long-Term Ecological Research (ILTER) program, initiated aproject to measure fundamental parameters affecting sustainable land use on an ecologicalrather than national basis. The project brings together Palestinian, Israeli, and US scientistsat Hebron University, the Ministry of Environmental Affairs of the Palestinian Authority, theMitrani Center for Desert Ecology of Ben-Gurion University, the Jewish National Fund, theVolcani Center of the Israel Ministry of Agriculture, and the University of New Mexico. Meteorological data is fundamental to environmental research and is inadequately measuredalong the rainfall and biodiversity gradient extending from the Negev desert to the plateausof the West Bank. A jointly-operated network of monitoring stations to collect andexchange measurements of meteorological and soil conditions was established at two Israeliand two Palestinian environmental research sites. The ILTER program provided the scientificcontext for the project, guidelines for monitoring and an international framework for sharingenvironmental data. The CMC provided the monitoring hardware as well as expertise innetwork and Internet communications. The regional partners provided the sites andresearch staff to operate the meteorological stations. UNM provided data and operationalexperience from a similar site in the U.S. A long-term goal of the project is for the Palestiniansites to join the ILTER program along with the Israeli sites.

desertecology 41

Soil factors as

indicators of

desertification processes

in an agro-ecosystem in

the northern Negev

desert

Zaady

microphytic soil crust

communities

Zaady

Patterns of cO2 exchange

in biological soil crusts

of successional age

Zaady

contribution of aeolian

particles to microphytic

soil crust patches

Zaady

Soil erosion is an all-inclusive term describing the deflation of the landscape by wind andwater. Flash floods during winter cause erosive activities in the basins and adjacentagricultural areas in the semi-arid parts of the Negev desert of Israel. This has led toformation of waterfalls, which erode streams and cause the loss of soil nutrients over time.Soil erosion in conjunction with human activities has greatly contributed to desertification inthis part of the Negev. We set out to examine the effects of soil erosion and agriculturalpractices in twelve eroded sites in the northern Negev Desert. Our contention was that soilerosion and agricultural activities would reduce soil quality. The results showed, in all theparameters investigated, that there were significant differences between sites. Areas above,below and at various distances from waterfalls showed significant differences. Ecological siteshad higher organic carbon than cultivated areas, meaning that land degradation is taking placein the adjacent farmlands. Biomass of plants in bioassay showed a positive correlation withthe amount of organic carbon, an indicator of reduction of soil quality in the adjoiningcultivated areas. There is a need to further characterize the soil and increase the number ofsites in the study area in order to conclusively determine soil quality and recommendcorrective measures with a view to combating desertification.With: Y. Gutterman and D. Ward, BIDR

This investigation is part of the ‘Savannization Project’, a program aimed at combating desertification initiated by the Jewish National Fund in cooperation with scientists from

Israel and the USA. We examined the processes of recovery of the microphytic soil crustafter disturbances. The disturbances were caused by construction of pits and mounds, byscraping the soil surface and by applying herbicides. A central assumption of theSavannization Project is that plant and animal production and diversity in arid regions dependon the distribution and abundance of microphytic soil crusts, which are major sources ofwater and nutrients for higher plants. Results show that soil crust recovery in the Negevtakes about seven to ten years. During this time, soil infiltration and soil erosion decreaseand moss density increases. Since natural recovery of soil crusts is not a very long process,we recommend that for a few years after a heavy disturbance, managers should preventhuman activities and grazing in order to allow the crust to recover. This is important asproductivity and diversity in the Negev are concentrated mainly in the shrub patches, whichdepend upon the supply of resources from the crust patches.

The objective of this research was to determine whether CO2 exchange rates could be usedas an indicator for determining the state of development and species or functionalcomposition of biological soil crusts in different successional stages. In order to do so, wequantified the CO2 exchange rates, i.e., CO2 assimilation and respiration, in samples fromdifferent microhabitats at two different sites in the Negev desert. The data sets obtained inthe course of this study show substantial net CO2 assimilation rates, which are in a rangesimilar to dark respiration rates. We found a substantial gradient of CO2 exchange for bothrespiration and photosynthesis in biological soil crusts of successional age. Hence, asecotypes containing such biological soil crusts with dominant photosynthetically activeorganisms are a widespread phenomenon in desert, boreal and arctic systems, theircontribution to the global cycling of trace gases and elements can be significant for globalbudgets.With: J. Kesselmeier, Max-Planck-Institut fur Chemie, Mainz, Germany.

We investigated the dynamics of airborne particles in the northern Negev desert and in theNegev highland region, and evaluated their contribution to microphytic soil crustdevelopment. Results show that aeolian accumulation and deposition on the south-facingslopes of the watershed were significantly higher than on the north-facing slope, but thehighest accumulation was obtained in the wadi. The size classes of the airborne particlesshow that almost no damage was caused by dust deposition, and that most of the particleswere fixed by the microphytic crusts and contributed to the soil depth.With: Z. Y. Offer, BIDR, Meteorology, Dept. of Energy and Environmental Physics.

The microphytic soil crust in theNegev highlands near Sede-Boqer(100mm average annual rainfall).

desertecology 42

The relationships

between lizard

distribution and

microphytic soil crust

successional trend in

arid sandy landscape

Zaady

The Nitrogen cycle in

dryland ecosystems

Zaady, Shachak

effect of microphytes on

the spectral reflectance

of vegetation

in drylands

Zaady, Shachak

The effects of grazing on

abiotic and biotic

parameters in semi-arid

ecosystem: a case study

from the northern

Negev desert, Israel.

Zaady, Shachak

In this study, we measured some of the physiological and geomorphological characters of thedifferent sandy surface substrates available to the lizards. We then compared the distributionof lizard burrows among the different substrates to the distribution of available sites. All fourparameters measured showed a similar pattern of decrease from the well developedpermanent crusts to the loose sand. The lizards strongly preferred the temporary crust,where 80%-94% of the burrows were dug. These results may have important implications forland management, because sandy areas that are over-trampled are often converted intocrustless sand. On the other hand, sandy areas inhabited by low densities of wildlife and withno livestock trampling, develop crusts with almost no disturbance and eventually turn intohard permanent crust that might not be suitable for small digging vertebrates.With: A. Bouskila, BIDR

In a series of ongoing studies, we examined and characterized several aspects of the nitrogencycle in dryland ecosystems. 1. When comparing the N-fixation potential of different microphytic crust and macrophyticpatch soil/litter types, we found that free-living N-fixing bacteria are important if desertpatchiness is taken into consideration. Higher rates of N-fixation were observed in soil frommacrophytic patches than in the soil crust material. The generally high C content of themacrophytic patch soil-litter, and the particularly high C-to-N ratio of the largest size classof this material, appear to facilitate N fixation in macrophytic patches.2. In order to a) evaluate the potential for microbial immobilization and denitrification tocompete with plants for N,; and b) determine the effect of litter on nutrient cyclingprocesses in desert soils, we sought to quantify available N production within macrophyticpatches and on the soil crust patches following rewetting events. Findings indicate that litterplays a strong role in conserving N following wetting events in Negev soils. Amounts of soilNH4+ and NO3- and microbial biomass N were reduced in litter-amended treatments,suggesting that significant quantities of N were sequestered in litter. Immobilization andrelease of N by litter may be especially important in the N cycle in desert ecosystems.With: P. Groffman, Institute of Ecosystem Studies, USA.

The objective of this study was to compare reflectance values of higher plants with those oflower plants in drylands. During the wet season, when microphytic crusts are green, theirreflectance values are similar to those of higher plants, while in the dry season, they aresimilar to those of soil. We found that the reflectance of lower plant communities may leadto misinterpretation of the vegetation dynamics and overestimation of ecosystemproductivity. From the remote sensing point of view, the biogenic crusts of microphyticcommunities should be considered as soil during the dry season and as vegetation during thewet season.With: A. Karnieli, BIDR

The aim of this study was to quantify the effects of grazing on the ecological system,especially soil parameters and vegetation. We monitored the diversity and composition ofthe plant community, herbaceous biomass, soil moisture, soil organic matter, habitatstructure, and quality of the vegetation for grazers (protein content and digestion).Monitoring was in both grazed and in ungrazed plots. Our results showed that grazing hadimmediate effects on the plant community and habitat structure: the density of plant speciesdecreased, vegetation community composition was affected and exposed soil surfaceincreased. When plant diversity, soil fertility, and soil moisture were considered, nocorrelation was found in relation to grazing. Therefore, the results helped to determinemanagement patterns for effective runoff cultivation and minimum soil erosion, as well asminimum disturbance of plant diversity and productivity. The significance of the research isthat it demonstrates that livestock grazing can be effective as a management tool whileimposing limited damage to the ecosystem.With: A. Perevolotsky, Volcani Center.

desertecology 43

The effect of herbicides

on flow of water, soil,

and nutrients

Zaady, Shachak

Infiltration through

three contrasting

biological soil crusts in

patterned landscapes in

the Negev, Israel

Zaady, Shachak

Our objectives were to examine the influences of chemical disturbances in a patchy systemon 1) the flow of water; 2) soil erosion; and 3) nutrient flows. We found that herbicidesdisturb the microphytic soil crust and alter the functioning of the desert ecological system.The destruction of the weeds did not significantly increase runoff, but rather caused damageto the microphytic community, resulting in the loss of soil and organic matter. The use ofherbicides in open areas that are covered with microphytic crust is not recommended. It canbe used for purposes of annual removal and increasing infiltration in small areas under trees.

We examined the role of soil crusts in infiltration processes in three contrastingenvironments in the northern, central and central-western Negev, Israel. Removal of a thincyanobacterial-dominant crust from a sandy dune at Nizzana in the central-western Negev,a well-developed lichen-dominant and a cyanobacterial-dominant crust from a loess-coveredhill slope at Sayeret Shaked in the northern Negev resulted in a three- to five-fold increasein sorptivity and steady-state infiltration under both ponding and tension. Removal of adepositional crust colonised by cyanobacteria from a loess floodplain at Sede Zin in thecentral Negev resulted in increased infiltration under tension, but no significant effect underponding. We attribute the lack of effect under ponding to exposure of surface silts to water,which resulted in clogging of matrix pores and surface sealing. We maintain that removal ofthe crusts in all three landscapes would influence resource flows, particularly redistributionof runoff water, which is essential for the maintenance of desert soil-surface patterning. Itwould also have marked effects on germination, establishment, and survival of vascular plantsand soil biota, leading ultimately to desertification.With: J. D. Eldridge, University of New South Wales, Sydney, Australia.

desertecology 44

Zvika Abramsky

Yoav Avni

Yoram Ayal

Amos Bouskila

Burt P. Kotler

Boris Krasnov

Yael D. Lubin

Ariel Novoplansky

Rivka Ofir

Berry Pinshow

Research InterestsPh.D. Colorado State University, 1976; ProfessorIncumbent of The Abraham and Bessie Zacks Chair in Desert EcologyCommunity ecology of desert rodents: Applying the theory of density-dependent habitat selection to measurethe magnitude and energetic costs of biotic interactions (competition within and between species andpredator-prey interactions).Phone: 972-8-646-1342 • Fax: 972-8-647-2890 • E-mail: zvika@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1998; ResearcherGeology: Morphotectonics; Erosion processes; Palaeogeographic reconstructions.Phone: 972-8-658-8754 • FAX: 972-8-658-6369 • E-mail: avni@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1978; Researcher Grade B Community ecology in relation to primary productivity; Desert community structure; Dynamics ofparasitoid-host interactions from the individual to the population; Dynamics of insect-plant interactions.Phone: 972-8-659-6774 • Fax: 972-8-659-6772 • E-mail: ayal@bgumail.bgu.ac.il

Ph.D. University of California at Davis, 1993; LecturerBehavioral and community ecology; Behaviors related to predation; Conservation of reptile species andhabitats; Mathematical models for behavioral studies. Phone: 972-8-659-6775/646-1278 • Fax: 972-8-659-6772 • E-mail: bouskila@bgumail.bgu.ac.il

Ph.D. University of Arizona, 1983; Associate ProfessorCommunity, evolutionary, and behavioral ecology; Optimal foraging and habitat use; Trade-off between foodand safety, implications of information available to foragers; Foraging games between predators and their prey;Mechanisms of coexistence among desert seed-eating birds and mammals; Applying foraging theory andmechanisms of species coexistence to conservation.Phone: 972-8-659-6785 • Fax: 972-8-659-6772 • E-mail: kotler@bgumail.bgu.ac.il

Ph.D. Moscow State University, 1986; Researcher Grade BAnimal ecology: Population and community ecology of small mammals; Animal behavior; Community ecologyof ground-dwelling arthropods; Host-ectoparasite relationships.Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: krasnov@bgumail.bgu.ac.il

Ph.D. University of Florida, 1972; Associate ProfessorBehavioral and evolutionary ecology of arachnids, particularly spiders: Behavioral adaptations to desertconditions, mating strategies, maternal care of young, social behavior, dispersal and population structure;Influence of habitat structure on spider species diversity. Phone: 972-8-659-6782 • Fax: 972-8-659-6772 • E-mail: lubin@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1990; LecturerEvolutionary ecology of plants; Plant morphogenesis; Phenotypic plasticity of plants; Life-history tactics andstrategies of plants; Information perception and processing by plants; Genetics of drought-responsive genes;Improving plant response to CO2 fertilization; Ecological implications of the wind dispersal of pine seeds.Phone: 972-8-659-6820 • Fax: 972-8-659-6821 • E-mail: anovopla@bgumail.bgu.ac.il

Ph.D. Ben-Gurion Universiy of the Negev, 1985; Researcher Grade CMolecular biology; Cell biology; Phytochemicals; SIgnal transduction; normal and cancer cells; immunology.Phone: 972-8-659-6773 • Fax: 972-8-658-2068 • E-mail: rivir@bgumail.bgu.ac.il

Ph.D. Duke University, 1975; ProfessorPhysiological ecology; Energy and water exchange between animals and the environment; Physiology ofthermoregulation and osmoregulation in desert animals; Avian respiration, thermoregulation, andosmoregulation, and their role in flight duration, particularly with respect to migrating birds; Biogeography ofbirds in the Negev; Body composition in migrating passerines; Blood-gas transport.Phone: 972-8-659-6773 • Fax: 972-8-659-6772 • E-mail: pinshow@bgumail.bgu.ac.il

desertecology 45

Josef Plakht

Uriel N. Safriel

David Saltz

Moshe Shachak

Georgy Shenbrot

Vladimir Sheinkman

David WarD

Ilan Yarom

Eli Zaady

Yaron Ziv

Ph.D. Moscow State University, 1978; Researcher Grade BGeomorphology: Geomorphological and Quaternary mapping, stratigraphy and palaeo-geography of theQuaternary.Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: josefp@bgumail.bgu.ac.il

Ph.D. Oxford University, 1967; ProfessorAvian ecology; Conservation ecology; Ecology of desertification and global climatic change, effects thereof onforage grasses and on the Chukar partridge; Ecological implications of the wind dispersal of pine seeds.Phone: 972-8-659-6700 • Fax: 972-8-659-6703 • E-mail: urielsf@bgumail.bgu.ac.il

Ph.D. Colorado State University, 1988; Senior LecturerWildlife management and conservation biology; Various aspects of wildlife population dynamics, includingungulate ecology; Mountain gazelles and harvesting; Ecology of small populations; Reintroduction of Arabianoryx and Persian fallow deer; Space-use patterns of wolves in the Golan; Human impact on wildlife; Ecologyof ibex populations.Phone: 972-8-659-6778 • Fax: 972-8-659-6772 • E-mail: dzaltz@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1976; Associate ProfessorWatershed ecology of arid lands; Ecology of desertification; Ecological management; Ecological systems; Roleof animals in the functioning of arid ecological systems.Phone: 972-8-659-6786 • Fax: 972-8-659-6772 • E-mail: shachak@bgumail.bgu.ac.il

Ph.D. Moscow State University, 1980; ResearcherZoology: Community ecology of desert animals; Endangered and rare species protection.Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: shenbrot@bgumail.bgu.ac.il

Ph.D. Institute of Geography of the Russian Academy of Sciences, 1981; Associate ResearcherGeography: Quaternary geology and geomorphology.Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: sheinkma@bgumail.bgu.ac.il

Ph.D. University of Natal, 1987; Associate ProfessorCo-evolution of plant-herbivore systems; Defensive and growth responses of plants to herbivores; Relativeeffects of mammalian and insect herbivores on plant communities; Conservation of multi-species herbivorysystems and endangered plants.Phone: 972-8-659-6781 • Fax: 972-8-659-6772 • E-mail: ward@bgumail.bgu.ac.il

Ph.D. University of Kansas, 1995; Researcher Grade CEntomology; Biodiversity; Systematics and taxonomy of flies; Biology, ecology and control of agricultural pests;Desert ecology; Environmental impact of modern settlement on drylands.Phone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: iyarom@bgumail.bgu.ac.

Ph.D. Hebrew University of Jerusalem, 1992; Researcher Grade CNutrient flows in dryland ecosystems; Soil desertification and restoration; Rhizosphere ecology; Soilmicrobiology and microbial ecology; Landscape and microphyte ecology.Phone: 972-8-659-6784 • Fax: 972-8-659-6772 • E-mail: zaady@bgumail.bgu.ac.il

Ph.D. University of Arizona, 1998; LecturerPopulation Ecology: species interactions and Coexistence; Habitat selection; Foraging behavior. Communityecology: Patterns of species; Diversity and community structure; the role of habitat distribution andarrangement in community organization.Species-area relationship. Landscape ecology: Effects of the physicalenvironment on the organization of communities. Conservation biology: Use of landscape-scale modeling forproviding management policies regarding nature reserves and endangered species and communities.Phone: 972-8-646-1373 • Fax: 972-8-647-2890 • E-mail: yziv@bgumail.bgu.ac.il

desertecology 46

Publications

Adams, N. J., B. Pinshow, L. Z. Gannes and H. Biebach. Body temperatures in free-flying pigeons. J. Comp. Physiol. B 169:195-199 (1999)Amir, N., M. E. A Whitehouse and Y. Lubin. Food consumption and competition in a communally feeding social spider, Stegodyphus dumicola

(Eresidae). Journal of Arachnology (in press) Ayal Y., M. Broza and M.P. Pener. Geographical distribution and habitat segregation of bushcrickets (Orthoptera : Tettigoniidae) in Israel. Israel

Journal of Zoology 45:64-76 (1999)Crouch, T., Y. Lubin and M.Bodasing. Dispersal in the social spider Stegodyphus mimosarum Pavesi 1883 (Araneae: Eresidae). Durban Museum

Novitates 23: 52-55 (1998)Eldridge, J. D., E. Zaady, M.Shachak, and C. Myers. Control of desertification by microphytic crusts in a Negev desert shrubland. Desertification

and Soil Processes: Sixth International Rangeland Congress Proceedings 1:111-113 (1999)Garb, J., B.P. Kotler. and J.S. Brown.. Consequences of seed size in foraging and species interactions among Negev Desert granivores. Oikos

88:291-300 (1999)Giladi, I. and B. Pinshow. Evaporative and excretory water loss during free flight in pigeons. J. Comp. Physiol. B. 169:311-318 (1999)Groffman, P., E. Zaady and M. Shachak. Microbial contribution to biodiversity at organism, landscape and ecosystem scales. In: Biodiversity in

Drylands; Towards a Unified Framework and Identification Research Needs. pp 32-39. Ben-Gurion University, Beer-Sheva, Israel (1999)Hoekstra T. and M.Shachak. (Eds.) Arid Lands Management - Toward Ecological Sustainability. Univ.of Illinios Press (1999)Johannesen, J. and Y. Lubin. Group founding and breeding structure in the subsocial spider Stegodyphus lineatus (Eresidae). Heredity, 82:677-686

(1999)Kotler, B.P. and J.S. Brown. Mechanisms of coexistence of optimal foragers as determinants of the local abundance and distributions of desert

granivores. J. Mammalogy 80:361-374 (1999)Kotler, B.P., J.S. Brown and M. Hickie. Fox squirrels as futures traders: feeding behavior in response to food storability. Amer. Midl. Nat. 142:77-86

(1999)Kotler, B.P., J.S. Brown and M. Knight. Habitat and patch use in hyraxes: there's no place like home? Ecology Letters 3:82-88 (1999)Krasnov, B., M. Hastriter, S. Medvedev, G. Shenbrot, I. Khokhlova and V. Vaschenok. Additional records of fleas

(Siphonaptera) on wild rodents in the southern part of Israel. Israel Journal of Zoology 45:333-340 (1999)Levacov, R. and E.Zaady. The effect of herbicides on resources flow in patchy Negev desert landscape. Ecology and Environment (In Hebrew,

abstract in English) 5:112-121 (1999)Markman, S., B. Pinshow and J. Wright. Orange-tufted sunbirds do not feed nectar to their chicks. Auk 116:257-259 (1999)Morris, D.W., J.S. Brown and B.P. Kotler. The geographical ecology of mammals. J. Mammalogy 80:361-374 (1999)Pasquet, A., R. Leborgne and Y. Lubin. Optimal foraging, predation risk and life history of a desert spider, Stegodyphus lineatus (Eresidae).

Behavioural Ecology, 10:115-121 (1999)Rosenzweig, M. L. and Y. Ziv. The echo pattern of species diversity pattern and process in flagrante delicto. Ecography 22:614-628 (1999)Saltz, D. A long-term systematic approach to reintroductions: the Persian fallow deer and Arabian oryx in Israel. Animal Conservation 1:245-252

(1998)Saltz, D., H. Schmidt, M. Rowen, A. Karnieli, D. Ward and I. Schmidt. The feasibility of applying remote sensing techniques for assessing grazing

impacts in hyper-arid environments. J. Range Management 52:500-507 (1999)Saltz, D., M. Shachak, M. Caldwell, S. T. A. Picket, H. Tsoar, J. Dawson, Y. Yom Tov, M. Weltz and R. Farrow. The study and management of

dryland population systems. In: Arid Lands Management - Towards Ecological Sustainability (Eds. T. W. Hoekstra and M. Shachak) pp75-96 University of Illinois Press (1999)

Schneider, J. and Y. Lubin. Intersexual conflict in spiders. Oikos (Special issue: Costs of Reproduction, Ed. H. Ylonen), 83:496-506 (1998)Shachak, M., S. T. A. Pickett, B. Boeken and E. Zaady. Managing patchiness, ecological flows, productivity, and diversity in dry lands: Concepts

and applications in the Negev desert. In: Arid Lands Management – Toward Ecological Sustainability. (Eds. T. Hoekstra and M. Shachak)pp 254-263 Univ. of Illinois Press, Urbana. 1999

Shenbrot, G., B. Krasnov, and I. Khokhlova. Notes on the biology of the bushy-tailed bird, Sekeetamys calurus, in thecentral Negev, Israel. Mammalia 63: 374-377 (1999)

Shem-Tov, S., E. Zaady, M. P. Groffman and Y .Gutterman. Soil carbon content along rainfall gradient and germination: a potentialmechanism for regulating of Plantago coronopus. Soil Biology and Biochemistry 31:1209-1217 (1999)

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Tielman, I. B., J. B. Williams, G. Michaeli and B. Pinshow. The role of the nasal passages in the water economy of Crested larks and Desert larks.Physiol. Zool. 72:219-227 (1999)

Ward, D., D. Saltz, M. Rowen and I. Schmidt. Effects of grazing by re-introduced Equus hemionus on the vegetation in a Negev erosion cirque.Journal of Vegetation. Science: 10:579-586 (1999)

Whitehouse, M.A.E. and Y. Lubin. Strategic interference competition by individuals in social spider foraging groups. Animal Behaviour 58:677-688(1999)

Zaady, E. Nitrogen cycle and the Negev desert patchiness. Ecology and Environment (In Hebrew, abstract in English) 5:70-76 (1999)Zaady, E.The role of microphytic soil crusts in desert ecosystems. Ecology and Environment (In Hebrew, abstract in English) 5:77-84 (1999)Zaady, E., R. Eliasaf, R. Yonatan, L. Dvash and A. Perevolotsky. The response of plant community to grazing: Plant and soil parameters that are

affected by grazing. Ecology and Environment (In Hebrew, abstract in English), 5:167-179 (1999)Ziv, Y., and J. A. Smallwood. Gerbils and pocket mice - interspecific competition and the temporal niche. In: Activity Patterns in Small Mammals

- a Comparative Ecological Approach (Eds. H. S. Halle and N. C. Stenseth) Ecological Studies pp 141 ff. Springer-Verlag, Berlin (2000)

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Technical staff

Secretarial staff

Visiting Scientists

Mitrani Department of Desert Ecology

Yael Bar-Ilan - Hazeva Research Station Moris Melnokov - Hazeva Research StationSol Brand Iris MuslyOfer Eitan Sonia RosinMarc Goldberg Galit ShiranDr. Vasiliy Kravchenko- Hazeva Research Station Dror TschoryMichal Laniado - Ramon Science Center Jum’aa ZanunRegina Levacov Natali Zeevi - Hazeva Research StationZafrir Levi

Yael KaplanTamar Livne - Hazeva Research StationRinat LukatsOrli Plotkin - Hazeva Research StationAvi Shushan - Ramon Science CenterGalit Sudery

Dr. Joel Brown, University of Illinois at Chicago, USAAmber Budden, University of Wales, Bangor - Hazeva Research StationDr. Tanza Crouch, Durban Natural Science Museum, South AfricaProf. Perry Eason, University of Louisville, USAProf. Deborah Goldberg, University of Michigan, USAAdam Green, University of Wisconsin, Madison Vladimir Gromov, Russian Academy of Science, Russia – Ramon Science CenterDr. José Gruenzweig, University of Alaska, USAProf. Ted Hammel, Indiana University, USAIrina Insarova, Moscow State University, Russia – Ramon Science CenterProf. Gotfried Jetschke, University of Jena, GermanyDr. Miklos Kertesz, Institute of Ecology and Botany of the Hungarian Academy of Sciences, HungaryGünter Müller, The Museum of Munich, and the Hebrew University of Jerusalem - Hazeva Research StationDr. Beata Oborny, Lorand Eotvos University, Budapest, HungaryMirjam Papke, University of Hamburg, GermanyProf. Henry Prange, Indiana University, USADr. Eric Rextad, University of Alaska, USAProf. David Robershaw, Cornell University, USADr. Jutta Schneider, University of Mainz, GermanySergei Semenov, Moscow State University, Russia Ramon Science CenterProf. Deborah Smith, University of Kansas, USADr. Andrei Tchabovsky, Severtzov Institute of Ecology and Evolution of Russian Academy of ScienceDr. Peter Turchin, University of Connecticut, USAProf. Roy Turkington, University of British Colombia, CanadaDr. Linda Wiener, St. John’s College, USAProf. Ron Ydenberg, Department of Biological Sciences, Simon Fraser University, USA

desertecology 49

PostdoctoralFellows

Graduate Students

Dr. Avner Anava - Hazeva Research StationDr. Sasha DallDr. Ali HarariDr. Greg JohnstonDr. Carmi KorineDr. Thomas RödelDr. Anna SherDr. Phillip TaylorDr. Ian van TetsDr. Mary WhitehouseDr. Andrew Wilby

Tania Acuna Hagai Halel Natalia RuizAram Aviram Sharon Halevi Hila ShamirNoa Avni Bruce Kahn Ehud ShaniAlona Bachi Moses Kirega Eyal ShochatMitchell Baker Anat Levi Madan ShresthaMichal Ben Dror Eliezer Lichtenstein Gil StavGil Ben Natan Chris Lortie Eric SummerBetina Berendonck Alex Maklakov Sergei VolisPablo Blinder Regev Manor Gideon WasserbergGil Bohrer Nir Maoz Kerstin WiegandShlomi Brandwin Shai Markman Nimrod YisraeliRami Buchnik Keren Or Hila ZachorAyelet Danino Yarden Oren Fenchan ZhangAnat De Mush Ofer Ovadia Merav ZivDini Deutsh Guy Peer Ido ZurimTamar Erez Steven PoustyGirmay Gebru Noam Ra’ananAdam Green Ornea Reisman-BermanEsther Guggenheim Lizzane RoxburgDror Hablena Nir Sapir