Soil properties across forest-clearcut edges in the southwestern interior of British Columbia

MSc. Thesis Proposal

Todd ReddingDepartment of GeographySimon Fraser University

April 5, 2000

1.0 IntroductionForest harvesting is a common feature of the British Columbia forest landscape. Clearcut harvesting can result in significant changes

to the environment of previously forested areas (Keenan and Kimmins 1993). Recently there has been increasing public objection to traditional clearcut harvesting methods on the grounds that it may negatively affect values such as wildlife, aesthetics and recreation (Keenan and Kimmins 1993, Vyse 1999). Silvicultural systems utilizing smaller cut blocks rather than large openings have been proposed as a more appropriate method of forest harvesting that would protect environmental values (Franklin and Forman 1987).

Clearcut harvesting creates edges between forested and harvested areas. Although these edges appear to cause an abrupt transition, these adjacent ecosystems may influence each other. This influence of adjacent ecosystems upon one-another is called an edge effect (Murcia 1995). Smaller openings have a larger length of edge per unit area harvested than larger openings, and therefore greater potential influence of edge effects (Franklin and Forman 1987).

A considerable amount of research has been carried out on edge effects for variables such as microclimate (Chen et al. 1993, Cadenasso et al. 1997, Camargo and Kapos 1995) and vegetation (Matlack 1993, Williams-Linera et al. 1998). Most studies have focused on edge effects into the remnant forest to determine if there is habitat degradation resulting from adjacency to the edge (Murcia 1995, Kremsater 1997). The magnitude of difference between forest and clearcut, and the distance over which the change occur are the key factors in describing edge effects. If the difference between forest and clearcut is small and the rate of change is fast, the edge effect is probably not important from a forest management perspective. Quantifying the significance and magnitude of edge effects in an ecologically meaningful way has proven difficult given different responses for different variables and different environments (Murcia 1995, Cadenasso et al. 1997).

The forest floor is the accumulated organic material over top of the mineral soil. The forest floor is an important reservoir for plant nutrients (Weetman and Webber 1972, Keenan and Kimmins 1993). Clearcut harvesting has an influence on forest floor chemical properties (Vitousek 1985), and authors have indicated that edge effects in microclimate will have implications for nutrient cycling (Chen et al. 1993, Saunders et al. 1999). There has only been limited research on changes in forest floor chemical properties across edges. The available results from studies on forest floor chemical properties show edge influences of approximately 15 meters into both the forest and clearcut (R. Griffiths personal communication), while others do not show clear patterns through space or time (Hope 1999). Edge related patterns of forest floor variables are messy, resulting from the inherent variability of forest floor and soil processes (Perry 1998) and insufficient sampling intensity (R. Griffiths personal communication). While the nutrient properties of the forest floor may not be directly responsible for regeneration success, edge effects in microclimate conditions in combination with forest floor nutrient availability could have an impact on tree growth.

The proposed research is part of a large interdisciplinary research project studying the ecology of a high-elevation forest at Sicamous Creek in the southern interior of British Columbia. With a large number of studies focused on forest floor and mineral soil processes, the Sicamous Creek site provides as excellent opportunity to study edges and forest floor variability (Perry 1998). The importance of understanding edge effects on belowground processes is an identified research need with implications for understanding the relationship between opening size and ecosystem resilience (Perry 1998). The proposed research will address the question of whether there is an edge effect in forest floor properties across edges of high elevation clearcuts in the southern interior of British Columbia.

The first section of this proposal reviews the literature on the effects of clearcutting and edges on forest floor properties. Physical and biological effects that influence forest floor chemistry are being described. Chemical effects of clearcutting are examined for pH, carbon, nitrogen and sulphur. There is a brief discussion of some causes of forest floor spatial variability. Edge effects are discussed for variables that influence forest floor chemical properties and a conceptual model of potential change in forest floor chemical properties across edges is presented. The next section is a brief description of the study site at Sicamous Creek. The final section describes the proposed research methods.

2.0 Literature Review

2.1 Forest Floor Physical and Biological Responses to ClearcuttingTo understand changes in forest floor chemical properties, it is helpful to have an idea of how physical and biological factors

influencing the forest floor are affected by clearcut harvesting. Effects on the physical environment include changes in temperature, moisture, and physical properties. Biological effects include changes in tree root dynamics, soil biota, canopy wash and stemflow, and litterfall and decomposition.

2.1.1 Soil TemperatureClearcut harvesting removes the forest canopy, exposing the ground surface to increased incoming solar radiation. The radiant

exchange surface moves from the top of the canopy to the ground surface resulting in greater temperature extremes at the forest floor (Keenan and Kimmins 1993, Fleming et al. 1998). These changes in temperature are influenced by the physical characteristics of the ground surface (Fleming et al. 1998), microtopographic setting (Stathers et al. 1990) and the proximity and orientation of logging slash (Hungerford and Babbitt 1987). Surface soil temperature increases after harvesting relative to uncut forest (Hungerford and Babbitt 1987, Frazer et al. 1990, Smethurst and Nambiar 1990a, Chen et al. 1993). Smethurst and Nambiar (1990a) found average surface soil temperatures of 1 to 2o Celsius higher in clearcuts compared to adjacent unharvested stands. A study in Montana found that forest floor temperature was less variable in a conventionally harvested plot than a whole tree harvested plot or unharvested control (Entry et al. 1986).

2.1.2 Soil MoistureThe influence of clearcut harvesting on forest floor moisture content is more complex than temperature changes. In general,

clearcutting increases soil moisture by decreasing the amount of precipitation intercepted by the forest canopy and by reducing the loss of water

1

through evapotranspiration by vegetation (Frazer et al. 1990, Keenan and Kimmins 1993, Elliot et al. 1998, Fisher and Binkley 2000). Smethurst and Nambiar (1990a) found that after clearcutting, precipitation reaching the forest floor increased by 146%. However, surface evaporation also increases after harvesting due to the increased temperatures (Smethurst and Nambiar 1990a). This can reduce the moisture content of the forest floor (Lowe 1993). It seems that most studies on changes in soil moisture resulting from clearcutting have been done from a hydrology perspective (i.e. how much water is available for runoff from a clearcut compared with an intact forest), and often do not consider the forest floor (e.g. Elliot et al. 1998, R. Adams personal communication).

Studies of nutrient cycling and soil biology have found that the moisture content of the forest floor is higher in uncut forest than in clearcuts (Johnson 1997, Prescott 1997, K. Hannam personal communication). This is probably the result of lower evaporative losses in the forest than in the clearcut (Lowe 1993). As regenerating stands reach canopy closure, the patterns of forest floor moisture between mature and regenerating forest become much more similar (Lowe 1993). In the clearcut, slash shades the forest floor from direct radiation resulting in higher soil moisture than in exposed areas (Hungerford and Babbitt 1987, Smethurst and Nambiar 1990a). Entry et al. (1986) found that forest floor moisture content was greatest in a conventionally harvested plot, intermediate in the uncut forest and lowest in the plot which had been whole-tree harvested. Changes in forest floor moisture content appear to be highly site specific (Keenan and Kimmins 1993, R. Adams personal communication).

2.1.3 Soil StructureClearcutting also can alter the physical structure of the forest floor and mineral soil (Borchers and Perry 1992). These changes can

include compaction, mixing and destruction of soil structure (Zinke 1983, Johnson et al. 1991a, Borchers and Perry 1992). Mixing of forest floor materials into mineral soil can result in increased decomposition and nitrogen mineralization due to increased soil temperature and moisture (Fisher and Binkley 2000). To address some of these problems in the interior of British Columbia, clearcut logging is commonly carried out in winter when there is a snow pack to protect the forest floor from disturbance.

2.1.4 Tree Roots and Soil BiotaRemoval of the forest canopy may result in changes to tree rooting dynamics and to the soil biota (Fisher and Binkley 2000). The

removal of the forest often results in the death of the root systems of the trees that were harvested. This is the case for conifers, but some deciduous species are able to re-sprout from existing root systems after disturbance (Perry 1994). There is a time lag between harvest and root mortality related to the slow desiccation of root materials, but most roots die within the first growing season after harvest (Fahey et al. 1988).

Fine roots are an important short-term source of carbon and nutrients following clearcut harvesting (Fahey et al. 1988, Knoepp and Swank 1997). Decomposition and nutrient release is greatest for fine roots (<0.6mm) in the first 2 years following harvest, while larger roots decompose and release nutrients much more slowly (Fahey et al. 1988). Within two years of harvest, the release of nitrogen from fine roots was approximately 18% of the total amount of nitrogen removed during a study of whole-tree harvesting in New England (Fahey et al. 1988). A study at Sicamous Creek in the southern interior of British Columbia found that fine root biomass is greater in unharvested stands than 4-year-old clearcuts in the spring (Welke and Hope 1999). There was no difference in biomass between treatments in the fall (Welke and Hope 1999). Nutrient content of fine roots did not differ between forest and openings (Welke and Hope 1999).

Mortality of fine roots has implications for the soil biological community as well. Without live roots, mycorrhizal fungi lose hosts. Studies have found that live conifer roots with active mycorrhizal root tips were greatly decreased at distances of 4.5, 6 and 16m respectively into a clearcut from the edge of a remnant forest (Harvey et al. 1980, Parsons et al. 1994b, Hagerman et al. 1999). Species of mat-forming ectomycorrhizal fungi are found much less frequently in recently clearcut (<5yr) areas than in established forest stands (Griffiths et al. 1996). These groups of fungi can have large influence on the spatial variability of nutrients (Griffiths et al. 1990, Griffiths et al. 1996). Additionally, the rhizosphere provides energy and nutrients for many soil microbes and micro-arthropods (Killham 1994).

Changes in soil temperature and moisture that occur with clearcutting can also affect the soil biological community (Entry et al. 1986). Increased soil moisture due to decreased plant uptake can provide a better environment for microbial activity (Parsons et al. 1994a). The ratio of bacterial to fungal biomass may increase after harvesting (Entry et al. 1986, Johnson 1997). Bacteria are better able to exploit newly available resources and changing environmental conditions due to more rapid growth and reproduction rates than fungi (Entry et al. 1986). Changes in microbial community structure should persist as long as post harvest changes in organic matter, soil temperature and moisture persist (Entry et al. 1986). Changes in soil temperature of 10o Celsius can result in a doubling of microbial activity (to a maximum temperature of 35oC), while temperature changes of as little as 1oC can increase root and shoot growth and nutrient uptake of plants (Killham 1994). Under laboratory conditions, rates of decomposition and nitrogen mineralization have been found to increase due to increases in microbial activity at higher soil temperatures (Macdonald et al. 1995, Zogg et al. 1997).

2.1.5 Canopy Wash and StemflowCanopy wash and stemflow provide potentially important sources of nutrient inputs to undisturbed forests, but are difficult to quantify

(Mahendrappa et al. 1986). With canopy removal, canopy wash will consist only of inputs from remaining understory vegetation. Stemflow is an important influence on the spatial variability of forest soil chemical properties (Boerner and Koslowsky 1989). These patterns will be retained after harvest but will not be renewed or enriched.

2.1.6 Litterfall and DecompositionThe removal of the forest canopy results in decreased inputs of canopy tree litterfall. Depending on the harvesting method employed,

there may be a large pulse of litter in the form of logging slash (Keenan and Kimmins 1993). Environmental and biological changes resulting from clearcut harvesting can influence the rate of decomposition of organic material remaining after harvest.

Decomposition is controlled by climate, soil organisms and litter quality (Couteaux et al. 1995, Moore et al. 1999), and is measured as the percentage dry mass loss over time (Prescott and Zabek 1999). Litter quality is generally considered to be better for more labile forms, those having a high carbon:lignin ratio (Couteaux et al. 1995, Moore et al. 1999, Prescott and Zabek 1999). The rate and intensity of biological activity may be altered by climatic changes resulting from clearcut harvesting (Couteaux et al. 1995, Perry 1998). Zogg et al. (1997) found that changes in soil temperature lead to changes in the community composition of the soil biota, and that decomposition occurs on different substrate (organic matter) pools at different soil temperatures. The general consensus has been that clearcut areas will have higher rates of decomposition as they have higher soil temperature and moisture and thus provide a more suitable environment for decomposer organisms (Keenan and Kimmins 1993, Fisher and Binkley 2000).

Some research has supported the assumption that decomposition rate is greater in clearcut than unharvested areas (Edmonds and Biggar 1983, Binkley 1984, Concannon 1995). Edmonds and Biggar (1983) found greater decomposition in clearcut areas. However, litter in the

2

forest lost more of its initial nutrients than did the more rapidly decomposed litter in the clearcut areas (Edmonds and Biggar 1983). Binkley (1984) found that decomposition increased in clearcuts as compared to uncut forest, at the F-H, and H-mineral soil interfaces of the forest floor. At the L-F interface, decomposition was the same as or greater in the forest than the clearcut, and that the magnitude of difference between forest and clearcut was site specific (Binkley 1984). A study in coastal Alaska found higher decomposition rates in the clearcut than the forest, and attributed this to differences in relative humidity, soil moisture and higher nighttime air temperatures (Concannon 1995). This study also found greater decomposition rates in younger clearcuts (1 year) than in older (5 years) ones (Concannon 1995).

Recent research in British Columbia has not found the same trend (Prescott 1997, Prescott and Zabek 1999, James 2000). Research on Vancouver Island by Prescott (1997) found greater decomposition rates in old-growth forest than in the adjacent recent clearcut. Prescott and Zabek (1999) describe a province-wide decomposition study in which decomposition rates in clearcuts are the same or less than in adjacent mature forest. Similar results have been found at Sicamous Creek in the southern interior of British Columbia, where there are no significant differences in decomposition rates between mature forest and clearcut areas (James 2000). A possible explanation for these results is that forest floor moisture content actually decreases after clearcutting. This is supported by results from Vancouver Island and from the interior of British Columbia (Johnson 1997, Prescott 1997, K. Hannam personal communication). Higher moisture content in combination with a more intact biological community in the forest could combine to offset the increases in soil temperature in the clearcut (Prescott 1997, Prescott and Zabek 1999). Forest floor microbial communities subjected to greater variability in forest floor moisture and temperature following clearcutting may not have adequate time to build-up populations before the environment changes enough that another functional group takes over. It is clear from the above discussion that, given the importance of decomposition for nutrient availability, this is an identified area needing further study (Keenan and Kimmins 1993, Prescott and Zabek 1999).

2.2 Effects of Clearcutting on Forest Floor Chemical PropertiesStudies of clearcutting effects on nutrient cycling and biogeochemistry have a long history (Bormann and Likens 1979), and some

general trends have been identified (Vitousek 1985, Keenan and Kimmins 1993). It is important to remember that changes in chemical properties and processes are also occurring in the undisturbed forest through time, so results must be interpreted carefully (Trettin 1999). Another important consideration is the units used to quantify changes. Commonly, studies will examine changes in both concentration and content of chemicals in the forest floor. The concentration is the amount of a chemical in a given unit of forest floor material (e.g. percent nitrogen or grams nitrogen per gram of dry organic matter). Content refers to the total amount of a chemical over a given area (e.g. kilograms nitrogen per hectare). Changes in concentration are not necessarily reflected in changes in content. For example, in decomposing forest floor the nitrogen concentration in remaining organic matter may increase, and the total content of nitrogen in the forest floor on the site may stay the same. In addition, not all studies are done on similar sites or with equivalent methods, making comparison of results difficult.

2.2.1 pHForest floor pH tends to decrease after harvest (Johnson et al 1991b, Schmidt et al. 1996, Krause 1998, Zhang 1999), followed by a

slow recovery with regeneration of vegetation cover (Krause 1998). The reasons proposed for increased acidity following harvest are; 1- increased nitrification (Johnson et al. 1991b, Zhang et al. 1999) or, 2- increased leaching of organic acids derived from slash, due to elevated soil moisture (Johnson et al. 1991b).

Not all studies have found decreased pH following clearcut harvesting. Brais et al. (1995) found decreased pH after harvest only on moist sites, and not on mesic or dry sites. They did not have a clear explanation for this result. In Douglas-fir forests in Oregon, a study found increased pH in clearcuts at 5 and 15 years after harvest (not statistically significant); by 40 years there was no difference (R. Griffiths personal communication). Entry et al. (1986) found higher pH in a conventionally harvested plot, with the uncut control intermediate and the whole-tree harvested plot having the most acid forest floor. Keenan and Kimmins (1993) report that there is considerable site-specific variation in clearcutting effects on pH.

2.2.2 CarbonClearcut harvesting involves the removal of carbon from a site in the form of plant biomass. The type of harvesting system used will

affect the amount of plant biomass remaining on site after cutting (Keenan and Kimmins 1993). Conventional clearcut systems can leave a considerable amount of slash material, while whole-tree harvesting removes much more organic material. Slash, such as leaves and branches, contains much of the labile carbon in the aboveground portions of the tree (Fisher and Binkley 2000). Both methods leave behind labile carbon in the form of decaying roots (Frazer et al. 1990). The harvesting process itself does not result in significant losses of forest floor organic matter; losses of carbon occur as a consequence of continued decomposition with a reduction in litter replenishment (Johnson 1992).

Conventional clearcut harvesting can result in an immediate increase in carbon content in the forest floor (Johnson 1992, Knoepp and Swank 1997). These are one-time inputs and generally, forest floor carbon content (carbon or organic matter mass/ha) decreases with time after clearcut harvesting due to both decreased inputs and to decomposition and respiration losses (Covington 1981, Smethurst and Nambiar 1990b, Johnson 1992, Brais et al. 1995, Krause 1998, Zhang et al. 1999). The magnitude of effects can be site specific, depending on the rate of decomposition and the quality of organic matter substrates. Brais et al. (1995) found that organic carbon was lost from dry and mesic sites after harvesting, but moist sites did not change. Decreased carbon concentrations in the forest floor have been measured in Alberta 20 months after harvesting (Schmidt et al. 1996).

Changes in organic matter content of the forest floor occur through time after harvest. The point in time after harvesting when decomposition and respiration losses of organic matter are balanced by litter inputs from the regenerating stand is termed the convergence point (Covington 1981). The time to convergence varies by site and species. Krause (1998) studied a chronosequence of regenerating jack pine and black spruce in New Brunswick, and found that the pine stands reached convergence after 6 years, while the spruce took approximately 10 years. Covington (1981) found convergence took 15 years for hardwood forests in New England. Prescott (1997) estimated it would take 20 years for the forest floor in a clearcut on Vancouver Island to be completely decomposed if there were no organic matter inputs from regenerating trees.

Loss of carbon in the forest floor after clearcutting is a complicated subject. Organic matter plays an important roll in regulating both chemical and physical properties and processes in the soil. Since most plant carbon is obtained from the atmosphere by photosynthesis (Fisher and Binkley 2000), the actual carbon reserves in the forest floor do not directly impact plant productivity. The indirect effects of carbon:nutrient ratios and their importance in microbial activity do impact nutrient availability in regenerating forest stands. The role of carbon in the retention of nitrogen in the forest floor after harvest is discussed in the following section.

3

2.2.3 NitrogenThe response of nitrogen to clearcutting is the most complex of the four chemical properties discussed in this paper, and for that

reason it will be examined in greater detail. Nitrogen is considered to be the nutrient most limiting to plant growth in most temperate coniferous forests and especially in the Pacific Northwest of North America (Vitousek 1985, Myrold 1999, Fisher and Binkley 2000). All methods of forest harvesting remove nitrogen that is incorporated into the biomass of stems and foliage (Fisher and Binkley 2000). Whole tree harvest has the potential to remove large amounts of nitrogen from the site, as the tree canopy (foliage and branches) often contains half of the total nitrogen within the tree (Keenan and Kimmins 1993, Fisher and Binkley 2000). The effects of harvesting on nitrogen will be discussed in terms of impacts on the total pool of forest floor nitrogen, and the effects of harvesting on sources of plant-available nitrogen (Figure 1).

Total nitrogen in the forest floor includes all of the pools of nitrogen (NH4+, NO3

-, microbial, organic and plant nitrogen) (Figure 1) within a given amount of forest floor material (Bremner and Mulvaney 1982). In Alberta, Schmidt et al. (1996) found small decreases in the nitrogen concentration in forest floor materials 20 months after harvest. Smethurst and Nambiar (1990a) found a small decrease in total nitrogen concentration after clearcut harvesting in Australia. Changes in total nitrogen content of the forest floor are related to harvesting method, with greater losses occurring from whole-tree harvesting than from conventional logging (Edmonds and Biggar 1983, Smethurst and Nambiar 1990b). Addition of logging slash can result in increases in total nitrogen content of forest floor, while whole-tree methods can result in a decrease (Knoepp and Swank 1997). Decreases in total nitrogen content occur from leaching and denitrification of available forms.

It has been accepted that plant available nitrogen is limited to nitrate (NO3-) and ammonium (NH4

+); however, plants may be able to use forms of organic nitrogen (Kaye and Hart 1997, Fisher and Binkley 2000). The importance of organic nitrogen uptake for plant nutrition is not well understood for forests, and is a focus of current research (Kaye and Hart 1997, H. Peat personal communication). Much of the research examining the effects of clearcut harvesting on plant available nitrogen has focused on the mineral soil and site preparation effects. For that reason, this review includes results from studies on mineral soil, as the response of forest floor and mineral soil may be similar.

The plant-available nitrogen pool is measured as the ammonium and nitrate in the soil solution. These forms of nitrogen are extracted using a salt solution, and the concentration is measured colorimetrically (Hart et al. 1994b). Most studies of nitrogen availability examine the rates at which mineralization and nitrification occur. Net nitrogen mineralization is measured as the total (gross) amount of mineralized nitrogen minus the immobilization by microbes (Hart et al. 1994b). This rate is measured by incubating samples in sealed bags or tubes inserted into the soil with roots excluded to eliminate the possibility of plant uptake, so the accumulated amount of mineral nitrogen is what is theoretically available to plants (Hart et al. 1994b). The amount of available nitrogen is determined by extracting the nitrate and ammonium pre- and post-incubation, with the difference being the net rate of mineralization (Hart et al. 1994b). The buried bag method integrates the effects of temperature, but not moisture, over the incubation period. Ideally this nitrogen pool should be termed extractable rather than available, as nitrate and ammonium can be immobilized by clay particles and not be available to plants or extractable in salt solution (Brady 1990).

Another method of determining plant-available nitrogen involves the use of ion exchange resins (Binkley and Hart 1989). This method is designed to measure the amount of available nitrogen moving by mass flow through the soil matrix (Binkey and Hart 1989). These resins remove nitrate and ammonium ions as they percolate through in the soil solution, and are then extracted using a salt solution (Binkley and Hart 1989). The method measures the mineral nitrogen that is actually available to plant roots, however it is limited by the need for adequate soil moisture for mass flow to occur through the resins (Binkley and Hart 1989). The lack of regular mass flow makes the ion exchange resin method of little use in dry ecosystems.

A popular lab method of determining potentially available nitrogen is the anaerobic incubation method (Binkley and Hart 1989). This method involves incubating samples in anaerobic conditions under constant temperature and moisture. Available forms and nitrogen incorporated in microbial biomass are converted to ammonium and the ammonium is extracted as with the other methods (Binkley and Hart 1989). This method gives a measure of potentially mineralizeable nitrogen (Binkley and Hart 1989).

The majority of literature indicates that available nitrogen in the forest floor, as measured using the methods described above, increases following clearcut harvesting (Binkley 1984, Vitousek 1985, Frazer et al. 1990, Smethurst and Nambiar 1990a, Parsons et al. 1994a, Prescott 1997, Titus et al. 1998, Prescott and Zabek 1999, James 2000). Conventional harvest generally results in greater available mineral nitrogen compared with whole-tree harvesting (Smethurst and Nambiar 1990a, Keenan and Kimmins 1993, Titus et al. 1998). The magnitude and longevity of changes appear to be site specific (Vitousek and Melillo 1979, Vitousek 1985, Myrold 1999).

Only one study was found that measured a decrease in available forms of nitrogen in the forest floor after clearcut harvesting (Schmidt et al. 1996). Decreased nitrate and ammonium concentrations from fresh samples were found at two sites in Alberta 20 months after harvest, where samples were collected in clearcuts and adjacent undisturbed forest (Schmidt et al. 1996). The same result was found for mineralizeable nitrogen using the anaerobic incubation method (Schmidt et al. 1996). The reasons presented for this outcome was loss of nitrogen to leaching, immobilization due to large carbon inputs in slash and disturbance and mixing of the forest floor with mineral soil during harvest (Schmidt et al. 1996).

There is considerable debate in the literature about why extractable nitrogen is greater in clearcuts than in undisturbed forests (Prescott and Zabek 1999, Stark and Hart 1999). The traditional view was that there was very little nitrate produced in undisturbed forests. Ammonium was preferred over nitrate by heterotrophic microbes, which were believed to dominate the soils in undisturbed forests. What nitrate was produced was immediately taken up by plants. After the forest was cut, there was decreased plant uptake plus increased decomposition and microbial activity. Therefore, the rates of nitrogen mineralization and nitrification increased, leading to accumulation of inorganic nitrogen in the soil solution without plant uptake.

Recent research has found that nitrate is produced in large quantities in intact forests, but is rapidly immobilized by heterotrophic microbes (Davidson et al. 1992, Hart et al. 1994a, Stark and Hart 1997). Mineralization rates from minutes to hours have been measured (Stark and Hart 1997). Nitrification rates were found to be two to three times greater in old-growth forest than in an adjacent ten-year-old plantation (Davidson et al. 1992). These studies measured gross rates of nitrogen mineralization and nitrification using nitrogen-15 labeling techniques. These methods allow for the measurement of actual rates of nitrogen mineralization and allow the researcher to track where the mineralized nitrogen ends up (i.e. soil solution, microbial biomass or plants) (Vitousek and Andarise 1986, Hart et al. 1994b). This has the advantage of not having to assume the fate of the mineralized nitrogen. Past studies assumed that ammonium was used by microbes and nitrate by plants. It is now clear that heterotrophic microbes are important consumers of nitrate as well as ammonium (Davidson et al. 1992, Hart et al. 1994a, Stark and Hart 1997). These studies also showed that the length of the incubation influences net nitrogen mineralization. Shorter incubations result in less available nitrogen because microbes are nitrogen limited not carbon limited (Davidson et al. 1992). During longer incubations, microbes have utilized the labile carbon, and cannot immobilize more nitrogen, leading to accumulation of available nitrogen in the soil solution (Davidson et al. 1992, Fisher and Binkley 2000). The annual flow through available nitrogen pools for both clearcut and forest is far greater than the size of the pools at any given time (Vitousek 1985, Fisher and Binkley 2000).

4

These findings and the potential for no difference in decomposition between forest and clearcut have lead to new ideas about the importance of carbon in regulating nitrogen availability in forest ecosystems (Hart et al. 1994a, Kaye and Hart 1997, Stark and Hart 1997, Myrold 1999, Prescott and Zabek 1999, Stark and Hart 1999, Fisher and Binkley 2000). Microbial immobilization of nitrate and ammonium in clearcuts may be limited by the availability of labile carbon sources (Stark and Hart 1999). This is the reason that old-growth forest has low extractable nitrogen; microbial immobilization is not limited by carbon availability, but by nitrogen availability (Kaye and Hart 1997). Therefore increased nitrate and ammonium in the clearcut may not result from increased rates of mineralization or nitrification, but from decreased microbial immobilization (Stark and Hart 1997, Prescott and Zabek 1999, Stark and Hart 1999). If this is indeed the case, the conservation of organic matter after harvesting is extremely important for the retention of nitrogen on site after harvest (Myrold 1999). It has long been known that logging slash acted as a nitrogen sink after harvest, and that this nitrogen was released slowly as the stand regenerated (Covington 1981). These new findings refine our understanding of the mechanisms of nitrogen cycling within both disturbed and undisturbed systems, allowing for improved management to maintain the productivity of the managed forest.

Increased nitrate and ammonium in the soil solution following harvest can lead to losses in nitrogen capital through leaching and denitrification (Robertson et al. 1987, Fisher and Binkley 2000). Most research has found that the amount of nitrogen lost to leaching is only a small percentage of the total annual pool cycled (Vitousek 1985, Titus and Malcolm 1992, Titus et al. 1998), or of the amount on site nitrogen lost in the removal of tree biomass from the site (Feller 1997). Nitrate is especially vulnerable to leaching losses under the conditions of high precipitation and coarse textured soils (Vitousek 1985, Fisher and Binkley 2000). Leaching losses of nitrate are especially important as it is often accompanied by the loss of potassium and calcium ions, and can cause eutrophication of aquatic habitats (Fisher and Binkley 2000). Denitrification is another mechanism of nitrogen loss; however, it is only important in areas with wet soils (Fisher and Binkley 2000).

2.2.4 SulphurThe effects of clearcut harvesting on the sulphur content of forest floor is not well documented in the literature. In Alberta, Schmidt et

al. (1996) found that total S concentration had decreased at 20 months post-harvest relative to an unharvested control. Studies at Hubbard Brook by Zhang et al. (1999) found that total sulphur concentration in the forest floor had increased after harvest. The total sulphur content of the site had stayed about the same after harvest, but individual constituents had changed (Zhang et al. 1999). One difficulty with this study is that the authors did not account for inputs of atmospheric sulphur from industrial pollution, though they mentioned that it was an important source of S in these systems. For this reason, it is hard to interpret whether the results truly reflect harvesting treatment effects.

2.3 Factors Influencing Forest Floor variabilitySpatial variability of forest floor is site specific and reflects the site features and disturbance history (Qian and Klinka 1995). This

variability could potentially mask the expression of edge effects in forest floor properties. A major portion of this research project will be the measurement of environmental and site factors that influence the variability of forest floor properties.

Microsites and microtopography can have significant influences on forest floor properties (Qian and Klinka 1995). Differences in microtopography within sites exceeded between site differences in soil temperature and moisture in a comparison of vine maple gaps and coniferous forest in coastal forest British Columbia (Schmidt et al. 1998). Studies of microclimate across edges have found patterns in air and soil surface temperature unrelated to the edge or vegetation structure that was attributed to microtopographic effects (Saunders et al. 1999). A major source of microtopographic heterogeneity is the pits and mounds that result from windthrow trees (Beatty and Stone 1986). These different features can result in differences in chemical properties such as decreased pH, litter accumulation and soil moisture on mounds compared to pits (Beatty and Stone 1986). Forest floor developed from coarse woody debris can have different chemical characteristics than forest floor developed on mineral soil (Klinka et al. 1995, Qian and Klinka 1995). Forest floor developed from decaying wood is more acidic and has less available nitrogen (Klinka et al. 1995).

The structure of the vegetation community can influence forest floor properties (Perry 1994). Studies in the Amazon have found that vegetation structure can overwhelm edge effects in soil moisture (Camargo and Kapos 1995). Forest floor properties can vary with distance from vegetation over short distances. A study by Boerner and Koslowsky (1989) found that ammonium concentrations were greater within two meters of a tree stem than farther away. Studies have also found different levels of carbon, nitrogen and pH associated with different species of trees within the same stand (Boettcher and Kalisz 1990, Finzi et al. 1998a, 1998b).

A further source of variability is the forest floor biotic community. Studies in Oregon have shown decreased pH and increased mineralizable nitrogen and carbon in soils colonized with mycorrhizal mat-forming fungi compared to soils from the same stand without mats (Griffiths et al. 1990). The distribution of mat-forming fungi is affected by clearcut harvesting, with different patterns found in forest and clearcut (Griffiths et al. 1996).

The forest floor is highly variable for a number of reasons, and it is important to understand what is driving some of this variability (Perry 1998). Interpreting edge effects in forest floor properties will be extremely difficult without an understanding of what is driving the inherent variability.

2.4 Edge Influences on Forest Floor Properties It is clear that there are differences between the physical, biological and chemical conditions of the forest floor in clearcuts and forests.

It is not clear how these conditions change through space. Does the change occur abruptly at the edge or is there a gradual shift in properties across the edge?

Forest-clearcut edge effects have been studied for variables such as wildlife habitat, vegetation composition and microclimate (Kremsater 1997). There have been few studies directly examining edge effects in soil and forest floor nutrients. Most previous research on edge effects has examined the influence of an opening on remnant forest, primarily for habitat conservation purposes (Murcia 1995, Kremsater 1997). It is important to recognize that different variables will have different edge effects that may not be synchronized through space or time (Cadenasso et al. 1997, Saunders et al. 1999). The purpose of this section is to briefly review the literature for edge effects on variables that may influence the chemical properties of the forest floor. This information will be combined with what we know about differences between forests and clearcuts to develop a conceptual model of how forest floor properties might change from forest to clearcut. This model is focused on changes in the first few years after harvest.

Studies of microclimate have shown that edge orientation (direction the edge is facing) is very important in determining the magnitude of edge effects (Chen et al. 1993, Chen et.al 1995; Cadenasso et al. 1997). Research in Oregon has found that north-facing edges have less direct solar radiation and consequently lower soil temperatures and higher soil moisture than other edge orientations (Chen et al. 1993, Chen et al. 1995). Soil moisture at north-facing edges was found to be higher than in the forest or the clearcut (Chen et al. 1995). Soil temperature at the edge was intermediate between the highest values in the clearcut and lowest in the forest (Chen et al. 1993, Chen et al. 1995). Cadenasso et al.

5

(1997) found that a north-facing edge had greater microclimatic influence into the opening than into the adjacent forest (i.e.- the forest was influencing the clearcut), and the effect was opposite on south-facing edges. Johnson (1997) found the highest forest floor moisture content at the edge with the forest intermediate and the center of the clearcut the lowest during late July 1996. In the Amazon, Kapos (1989) found soil moisture was lowest at the edge and highest in the forest.

The composition and structure of vegetation communities can be influenced by edge effects. Stronger effects on vegetation community composition within the forest have been measured on south-facing edges than north facing. Fraver (1994) found that vegetation composition showed effects into the forest up to 60 meters from south facing edges and only 30 meters on north-facing edges. Palik and Murphy (1990) found effects of 20 meters into the forest on south facing and 5 meters on north-facing edges. At Sicamous Creek in British Columbia, edge effects on vegetation have been most strongly expressed for bryophytes (Brand et al. 2000). Bryophyte richness was greater into the opening on north-facing edges than south facing edges (Brand et al. 2000).

Research on the effects of adjacent forests on regeneration of clearcuts has also been carried out. In the southeastern United States, the density of naturally regenerating spruce and fir decreased with distance from the edge due to decreased seed fall (Hughes and Bechtel 1997). In a coastal Oregon clearcut, Hansen et al. (1990) found decreased height and diameter growth of planted Douglas-fir saplings within 20 meters of a north-facing edge. The authors attributed this growth decline to the shading effect of the adjacent forest (Hanson et al. 1990).

The structure of soil biological communities also changes across edges. Studies of mycorrhizal communities have shown a sharp decrease in diversity and density of ectomycorrhizal fungus into the clearcut from the edge (Harvey et al. 1980, Parsons et al. 1994b, Hagerman et al. 1999, Durall et al. 1999). Much of this decrease seems to occur around 6 meters from the edge into the clearcut, and is attributed to this being the edge of the zone of live roots from the adjacent forest (Harvey et al. 1980, Parsons et al. 1994b). Research in the southern interior of British Columbia has also found differences in microbial and fungal biomass at the edge relative to the forest and clearcut (Johnson 1997). Fungal biomass was highest in the forest, intermediate at the edge and lowest in the clearcut, while bacterial biomass showed the opposite trend (Johnson 1997). Soil dwelling invertebrates may also be influenced by forest edges (Phillips 1999). A limitation of these studies is the low resolution of measurement does not allow for a clear understanding of the rate of change across the edge.

Studies have examined edge effects on litter decomposition rates. In the southern interior of British Columbia, litter decomposition was not significantly different between forest and clearcut, and there was no edge-related pattern (Prescott and Hope 1997, Hope 1999). A study of decomposition versus distance from the edge into an Amazonian forest showed inconsistent patterns, which the author related to site variability (Didham 1998). Concannon (1995) found differences in decomposition between forest and clearcut. Most of the change in decomposition rate occurred very close to the edge, and there was no clear gradient, possibly as a consequence of the low sampling intensity across the edge (Concannon 1995).

Forest floor chemical properties vary with distance from the edge. Research in Oregon has found increases in pH from forest to clearcuts, with a zone of change approximately fifteen meters wide (R. Griffiths personal communication). Studies in British Columbia have found that the edge is intermediate between the maximum values in the clearcut and minimum values in the forest for extractable nitrate and ammonium (Johnson 1997). A study of distance from the edge across a ten-hectare clearcut near Sicamous, British Columbia has not shown consistent patterns in nitrogen mineralization related to distance from the edge (Prescott and Hope 1997, Hope 1999). The lack of a pattern may be a result of low sampling resolution combined with very spatially heterogeneous forest floor properties and processes.

Changes in variables that influence forest floor chemical properties across north and south facing edges are presented in Figure 2. It is likely that site-specific variation will result in considerable variability around the major trends. Combining the influences discussed above with what we know about the effect of clearcutting on forest floor chemical properties, we can develop a conceptual model for these properties across north and south facing edges (Figure 3). This model shows that the changes are not symmetrical across north and south facing edges. This is a result of differences in radiation inputs. The north-facing edge shades the clearcut near the edge, while on the south-facing edge radiation is able to penetrate between the tree stems and warm soils within the forest (Chen et al. 1995, Cadenasso et al. 1997).

3.0 Research Objectives

1- To determine if there is an edge effect in forest floor chemical properties at a high-elevation site in the southern interior of British Columbia.

2- To examine the differences in edge effects in forest floor chemical properties associated with north and south facing edges.

3- To examine the importance of the edge as a source of variability in forest floor chemical properties relative to other environmental factors.

4.0 The Sicamous Creek Silvicultural Systems ProjectThe Sicamous Creek Silvicultural Systems Project is an interdisciplinary study of a high-elevation spruce-fir forest ecosystem located

near Sicamous in the southern interior of British Columbia. The study area is within the Englemann Spruce-Subalpine Fir wet cold (ESSFwc2) biogeoclimatic subzone (Lloyd et al. 1990). This is the most common ESSF subzone in the southern interior of British Columbia and is found in the Nelson, Kamloops and Cariboo forest regions (Lloyd and Inselberg, 1997).

The site is located at the headwaters of Sicamous Creek in the Shuswap Highlands (Holland 1976). The study site has an elevation range of approximately 1550 to 1800 meters above sea level with a north facing aspect and slopes of 20-40%. Average annual precipitation is approximately 1000 millimeters and deep snow packs often last until mid-June. The mean annual temperature is 1oC (Lloyd and Inselberg 1997), and soil temperature at 2cm ranges from 0oC in the winter to approx 11oC in August (R. Adams personal communication). Parent materials are glacial till derived from coarse-grained metamorphic bedrock with discontinuous fluvial veneers. The soils on mesic sites have been described as silty-loam Orthic Humo-Ferric Podzols with a Hemimor humus form (Hope, 1997).

The forest at Sicamous Creek is dominated by Englemann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) with a maximum age greater than 300 years old (Parish et al. 1999). Understory vegetation on mesic sites is dominated by a black huckleberry (Vaccinium membranaceum) and white-flowered rhododendron (Rhododendron albiflorum) shrub layer (Lloyd et al. 1990). The herb layer is dominated by oak fern (Gymnocarpium dryopteris), and Sitka valerian (Valeriana sitchensis), with red-stemmed feather moss (Pleurozium schreberi) the dominant bryophyte (Lloyd et al. 1990).

Harvesting treatments consist of control (uncut), partial cut, 0.1, 1.0 and 10ha clearcuts logged in the winter of 1994/95. Site preparation consisting of mounding with an excavator was carried out in the late summer of 1995. Englemann spruce seedlings were planted in the early summer of 1996. Logging slash was manipulated on some areas of the 10ha openings as part of a study on small mammal habitat.

6

4.1 Related Research at Sicamous CreekA number of studies relevant to this research are ongoing at the Sicamous Creek. Nitrogen mineralization and litter decomposition are

being studied in all treatments to examine opening size effects (Prescott and Hope 1997, James 2000). A transect has been repeatedly sampled across one 10ha opening to examine edge effects on decomposition and nitrogen mineralization (Prescott and Hope 1997). Other relevant studies include soil productivity (Hope 1997), nutrient cycling (Feller 1997), soil organic nitrogen dynamics (K. Hannam personal communication), ectomycorrhizae (Hagerman et al. 1999), fine root biomass and turnover (Welke and Hope 1999), soil micro arthropods (Nadel 1997), soil food webs (Johnson 1997), vegetation (Lloyd et al. 1997, Brand et al. 2000) and microclimate (R. Adams personal communication). Descriptions of all research projects at Sicamous Creek are available in Hollstedt and Vyse (1997). A number of these studies have included a component designed to examine edge effects, however many do not have the spatial resolution or sampling intensity necessary to adequately describe these effects.

5.0 Methods

5.1 Site SelectionThe objective of this study is to examine patterns of forest floor properties across high-elevation forest-clearcut edges. North and

South facing edges will be selected from suitable 1 ha openings with a predominantly mesic site series at the Sicamous Creek site.

5.2 Sampling DesignTwo sampling strategies will be used in this study to examine edge effects on forest floor properties. At two of the selected openings,

transects will be sampled, while the third opening will have an intensively sampled grid comprised of five parallel transects.Transect sampling will extend from 50m from the south edge in the forest, across the opening (100m) and 50m into the forest on the

north side. The edge location (0 meter distance) will be at the edge as defined by the stems of mature trees in the remnant forest. Samples will be collected in the forest at distances of 0, 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, 50 meters from the edge. In the clearcut, samples will be collected at distances of 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 82, 84, 86, 88, 90, 92, 94, 96, 97, 98, and 99 meters from the south edge. A total of 73 samples will be collected along each transect. At each sampling distance, 3 individual samples will be collected and composited into a single sample to be analyzed for chemical and physical properties. All samples will be collected within 2m east or west of the transect line, at the required distance from the edge.

The intensive sites will be measured using a stratified grid layout. Five parallel transects separated by five meters will be laid out, with the 0 meter location being the edge of the mature stems in the forest. Samples will be collected and environmental conditions will be measured at the same intervals as the transect sampling for both the forest and clearcut. Along the sampling axis perpendicular to the edge, samples will be taken at distances within 2 meters east or west of the axis if an appropriate sampling location is not available directly on the grid point. Unsuitable sampling locations include site preparation pits and mounds, slash piles, soil wood and exposed mineral soil. Exact locations of each sampling location will be measured. At each sampling location, a composite sample consisting of 3 individual samples will be collected.

5.3 Forest floor samplingSamples will be collected from physically undisturbed forest floor only. Samples will be collected at least one meter away from skid

trails, coarse woody debris or site preparation mounds and pits. All forest floor material will be excavated using a ten by ten centimeter template to the forest floor – mineral soil interface and an average depth will be calculated using eight measurements of the sides of each excavated sample. Fresh litter will be scraped from the top of each sample. The depth measurements will be used in calculations of bulk density. A subsample from each location will be weighed, oven-dried at 70o Celsius for 48 hours and then re-weighed to calculate the moisture content.

Samples to be used for chemical analysis will be air dried in paper bags at the Kamloops Forest Service laboratory, and then sieved to remove large woody material such as branches and roots greater than 1 centimeter (Carter and Lowe 1986). The remaining forest floor materials will be mixed by hand and a subsample will be ground through a micro-hammer mill, placed in labeled sample boxes and sent for chemical analysis.

5.4 Forest floor chemical analysisChemical analyses of forest floor pH, total C & N and mineralizable N will be carried out at the British Columbia Ministry of Forests

Analytical Chemistry laboratory in Victoria. While my samples are being analyzed, I will visit the lab to observe the analysis process. In addition, field incubated nitrogen mineralization will be measured using the buried bag method at the intensive site only. The buried bag extractions will be carried out at SFU and analyzed at the UBC soils lab.

5.4.1 pHForest floor pH will be measured following the methods of Kalra and Maynard (1991) using a glass electrode-calomel electrode pH

meter. Calibration with standard buffer solutions will be carried out periodically during sampling. For each sample, five grams of forest floor material will be mixed with 10ml of 0.01M CaCl2 solution, mixed intermittently for 30 minutes and left to settle for 30 minutes. The active acidity will then be measured in the 1:2 forest floor-CaCl2 slurry.

5.4.2 Total C, N and SAnalysis for forest floor total carbon and nitrogen will be carried out using the combustion method. This method involves the

combustion of the sample in a very hot furnace, followed by the analysis of the combustion gases. The analysis is carried out with a Leco NCS analyzer (C. Dawson, personal communications).

5.4.3 Mineralizable NitrogenAll forest floor samples will be analyzed for mineralizable N using the anaerobic incubation method following Keeney (1982). Forest

floor samples will be re-moistened and incubated for 14 days at thirty degrees Celsius under waterlogged conditions. The soil anaerobes in the sample convert easily mineralized forms of organic and inorganic nitrogen to ammonium. The ammonium is extracted in 1M KCl solution and measured in an autoanalyzer.

7

5.5 Nitrogen MineralizationNitrogen mineralization will be measured at all sampling locations on the intensive site using the buried bag method following the

methods of Hart et al. (1994b). At the beginning of the incubation period, 3 subsamples will be collected at each sampling location to provide pre-incubation values with which to compare the incubation results. Field incubation involves collecting a small intact sample of forest floor and incubating it in the field in polyethylene bags. Three samples will be incubated individually at each sampling location. The samples will be incubated at the forest floor-mineral soil interface for approximately six weeks from mid-July to late August. Samples will be collected from the field and immediately transported in coolers to the SFU soils lab. Samples will be stored at four degrees Celsius until processing within one week of collection.

Samples will be removed from bags and sieved through a no. 4 sieve to remove the large pieces of wood and rocks. A fifty-gram subsample will be taken from each of the 3 samples at each location. These subsamples will be mixed, and 10 grams will be removed and used for extraction. Another 50 grams will be removed and used to determine moisture content by drying at 70oC for 48 hours. The 10 gram subsample will be placed in a whirl-pak bag and 100 ml of 2M KCl will be added to the bag and shaken for one hour and then left to settle in the fridge for one hour. The resulting slurry will be filtered through Whatman No. 42 equivalent pre-leached syringe filters into acid-washed nalgene bottles. Extracts will be stored at 4o Celsius after filtering. The extractants will be sent to the UBC soils laboratory for colorimetric analysis of nitrate and ammonium using a LaChat autoanalyzer.

5.6 Measurement of Environmental Variables

5.6.1 Forest Floor MoistureMoisture content will be determined for the forest floor and upper mineral soil (0-5cm). Forest floor moisture content will only be

determined once at the transect sites; the intensive sites will be re-measured twice over the growing season. The initial measurements at all sites will be done gravimetrically. Subsequent measurements of moisture content at the intensive sites will be carried out using a hand-held Delta-T probe and moisture meter (reference?), with gravimetric samples (10% of all samples) collected for calibration and quality control purposes.

5.6.2 Forest Floor TemperatureOver the growing season, forest floor temperature will be measured concurrently with soil moisture on the intensive sampling grids.

Copper-constantan thermocouples will be placed at the forest floor-mineral soil interface since this depth will be used for the buried bag incubations. A hand-held digital temperature reader will be attached to the thermocouple to record the temperature readings. Measurements will be carried out late in the afternoon, beginning in the clearcut and proceeding across the edge into the forest. This will partially account for the lag time in the soil-atmosphere transfer of heat, and allow us to obtain daily maximum readings (W. Bailey personal communication).

On each of the edge transects, temperature will be measured manually by inserting a probe at the forest floor-mineral soil interface. Three measurements will be taken adjacent to each of the five sub-sampling locations and then averaged for each distance from the edge.

5.6.3 MicrotopographyThe microtopography at each sampling point will be classified into categories such as pit, mound or depression to provide a

descriptive classification of each sampling location similar to Saunders et al. (1998). Categories will be determined during site selection based on site characteristics

5.6.4 Vegetation and Site SeriesVegetation at each sampling location (described as presence or absence of individual species within a 1 meter square area) will be

noted. Total cover of each vegetation layer (shrub, herb and bryophyte) will be recorded for each location. Site series will be determined in the field for each sampling location based on the classification set out in Lloyd et al. (1990), and using the same area as the vegetation sampling.

5.6.5 Substrate TypeThe humus form type at each sampling location will be described according to the classification system of Green et al. (1993).

Sampling of forest floor developed from soil wood will be avoided. Adjacency of sampling locations to deposits of slash or soil wood will be noted as well as the state of decay and size of the material. The presence of mycorrhizal fungal mats will be noted as the presence or absence in the 3 subsamples collected at each location.

5.6.6 Forest Stand Structure and Understory Light AvailabilityFor each sampling location, the distance to the nearest mature tree or stump will be measured, and species will be noted.A measurement of light reaching the forest floor will be made at all sampling locations to use as an index of differences in incoming

radiation. Measurements will be taken at a constant height of 0.5m using a LiCor LAI-2000 (Gendron et al. 1998).

5.7 Data AnalysisAll data will be entered into excel spreadsheets. The data will be examined for normality and transformed as required. Summary

statistics will be computed for all variables. Data analysis will be carried out using S-Plus (Mathsoft Corporation 1999) and CANOCO (TerBraak 1998).

Graphical methods will form a major portion of the data analysis. The data for all transects and variables will be graphed versus distance from the edge. Graphical methods may include standardizing variables to be graphed across the edge or using moving averages (Johnston et al. 1992, Saunders et al. 1999). Other potential methods of examining change across the edge include regression techniques (Cadenasso et al. 1997), edge finding algorithms (Fortin 1994) and depth of edge influence methods (Chen et al. 1993, Saunders et al. 1999).

For the intensive site, the previously mentioned methods will also be used for the individual transects of the grid or for averaged values of all transects. The spatial nature of this data set will allow the use of geostatistical and spatial statistical methods to examine spatial patterns (Legendre and Fortin 1989). Some of these methods might include variograms, kriging, Moran’s I and Geary’s C (Legendre and Fortin 1989). Wavelet analysis will be used to examine spatial patterns in the data for both transect and grid sites (Bradshaw and Spies 1992, Dale and Mah 1998, Saunders et al. 1998). Before wavelet analysis is carried out, the data will be gridded to a regular spacing using splines (Davis 1986) or analytical methods (C. Coburn personal communication). Edge finding algorithms may also be used to examine differences in edges for different variables (Fortin 1994).

8

Direct gradient analysis methods such as partial canonical correspondence analysis or partial redundancy analysis will be used to partition the variability between spatially structured, environmental and random components (Borcard et al. 1992, Legendre and Legendre 1998, Asselin et al. 2000). This will allow us to examine the relative influence of distance from the edge relative to other environmental factors, on variability of forest floor properties.

9

7.0 Literature Cited

Asselin, H., Fortin, M-J. and Bergeron, Y. 2000. Spatial distribution of late-successional coniferous species regeneration following disturbance in southwestern Quebec boreal forest. Forest Ecology and Management. Submitted.

Beatty, SW, and Stone, E.L. 1986. The variety of soil microsites created by tree falls. Canadian Journal of Forest Research. 16: 539-548.

Binkley, D. 1984. Does forest removal increase rates of decomposition and nutrient release? Forest Ecology and Management. 8: 229-233.

Binkley, D. and Hart, S.C. 1989. The components of nitrogen availability assessment in forest soils. Advances in Soil Science. 10: 57-112.

Boerner, R.E.J., and Koslowsky, S.D. 1989. Microsite variations in soil chemistry and nitrogen mineralization in a beech-maple forest. Soil Biology and Biochemistry 21 (6): 795-801.

Boettcher, S.E., and Kalisz, P.J. 1990. Single-tree influence on soil properties in the mountains of eastern Kentucky. Ecology. 71 (4):1365-1372.

Borcard, D, Legendre, P., and Drapeau, P. 1992. Partialling out the spatial component of ecological variation. Ecology. 73(3): 1045-1055.

Borchers, J.G., and Perry, D.A. 1992. The influence of soil texture and aggregation on carbon and nitrogen dynamics in southwest Oregon forests and clearcuts. Canadian Journal of Forest Research. 22: 298-305.

Bormann, F.H., and Likens, G.E. 1979. Pattern and Process in a Forested Ecosystem. Springer-Verlag, New York, USA.

Bradshaw, G.A., T.A. Spies. 1992. Characterizing canopy gap structure in forests using wavelet analysis. Journal of Ecology. 80: 205-215.

Brady, N.C. 1990. The Nature and Properties of Soils. Macmillan Publishing Company. New York, NY.

Brais, S., Camire, C. and Pare D. 1995. Impacts of whole-tree harvesting and winter windthrowing on soil pH and base status of clayey sites of northwestern Quebec. Canadian Journal of Forest Research. 25: 997-1007.

Brand, N., Miege, D. and Lloyd, D.A. 2000. Vegetation response to clearcut edges in the ESSFwc2 at the Sicamous Creek research site. Unpublished Working Paper prepared for: British Columbia Ministry of Forests, Kamloops Region.

Bremner, J.M. and Mulvaney, C.S. 1982. Nitrogen – Total. In Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties. Soil Science Society of America, Madison, WI. pp. 595-624.

Cadenasso, M.L., Traynor, M.M. and Pickett, S.T.A. 1997. Functional location of forest edges: gradients of multiple physical factors. Canadian Journal of Forest Research. 27:774-782.

Camargo, J.L.C., and Kapos, V.. 1995. Complex edge effects on soil moisture and microclimate in central Amazonian forest. Journal of Tropical Ecology. 11 (205-221): 205-221.

Carter, R.E., and Lowe, L.E. 1986. Lateral variability of forest floor properties under second-growth Douglas-fir stands and the usefulness of composite sampling techniques. Canadian Journal of Forest Research. 16: 1128-1132.

Chen, J., Franklin, J.F. and Spies, T.A. 1993. Contrasting microclimates among clearcut, edge and interior of Douglas-fir forest. Agricultural and Forest Meteorology. 63: 219-237.

Chen, J, Franklin, J.F. and Spies, T.A. 1995. Growing season microclimatic gradients from clearcut edges into old-growth Douglas-fir forests. Ecological Applications. 5 (1):74-86.

Concannon, J.A. 1995. Characterizing Structure, Microclimate and Decomposition of Peatland, Beachfront, and Newly Logged Forest Edges in Southeastern Alaska, College of Forest Resources, University of Washington, Seattle, WA.

Couteaux, M-M., Bottner, P. and Berg, B. 1995. Litter decomposition, climate and litter quality. Trends in Ecology and Evolution. 10 (2): 63-66.

Covington, W.W. 1981. Changes in forest floor organic matter and nutrient content following clear cutting in northern hardwoods. Ecology. 62 (1): 41-48.

Dale, M., and Mah, M. 1998. The use of wavelets for spatial pattern analysis in ecology. Journal of Vegetation Science. 9:805-814.

Davidson, E.A., Hart, S.C., and Firestone, M.K. 1992. Internal cycling of nitrate in soils of a mature coniferous forest. Ecology. 73(4): 1148-1156.

Davis, J.C. 1986. Statistics and Data Analysis in Geology (2nd Edition). New York, John Wiley and Sons.

Didham, R.K. 1998. Altered leaf-litter decomposition rates in tropical forest fragments. Oecologia. 116: 397-406.

Durall, D.M., Jones, M.D., Wright, E.F., Kroeger, P., and Coates, K.D. 1999. Species richness of ectomycorrhizal fungi in cut blocks of different sizes in the Interior Cedar-Hemlock forests of northwestern British Columbia: sporocarps and ectomycorrhizae. Canadian Journal of Forest

10

Research 29:1322-1332.

Edmonds, R.L., and Biggar, C.M. 1983. Decomposition and nitrogen mineralization rates in Douglas-fir needles in relation to whole-tree harvesting practices. Paper read at New Forests for a Changing World: Proceedings of the 1983 Convention of the Society of American Foresters, at Portland, Oregon. pp. 187-192.

Elliot, J.A., Toth, B.M., Granger, R.J., and Pomeroy, J.W. 1998. Soil moisture storage in mature and replanted sub-humid boreal forest stands. Canadian Journal of Soil Science. 78: 17-27.

Entry, J.A., Stark, N.M. and Loewenstein, H. 1986. Effect of timber harvesting on microbial biomass fluxes in a northern Rocky Mountain forest soil. Canadian Journal of Forest Research. 16: 1076-1081.

Fahey, T.J., Hughes, J.W., Pu, M., and Arthur, M.A. 1988. Root decomposition and nutrient flux following whole-tree harvest of northern hardwood forest. Forest Science. 34 (3): 744-768.

Feller, M. 1997. Influence of harvesting on the nutrient status of ESSFwc2 ecosystems. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp 121-133.

Finzi, A., Canham, C., and Van Breemen, N. 1998a. Canopy tree-soil interactions within temperate forests: species effects on pH and cations. Ecological Applications. 8 (2):447-454.

Finzi, AC, Van Breemen, N. and Canham, C.D. 1998b. Canopy tree-soil interactions within temperate forests: species effects on soil carbon and nitrogen. Ecological Applications. 8 (2):440-446.

Fisher, R.F., and Binkley, D. 2000. Ecology and Management of Forest Soils, 3rd Edition. John Wiley and Sons. Toronto.

Fleming, R.L., Black, T.A., Adams, R.S., and Stathers, R.J. 1998. Silvicultural treatments, microclimatic conditions and seedling response in southern interior clearcuts. Canadian Journal of Soil Science. 78: 115-126.

Fortin, M.-J. 1994. Edge detection algorithms for two-dimensional ecological data. Ecology 75 (4):956-965.

Franklin, J.F., and Forman, R.T.T. 1987. Creating landscape patterns by forest cutting: Ecological consequences and principles. Landscape Ecology. 1(1): 5-18.

Fraver, S. 1994. Vegetation responses along edge-to-interior gradients in the mixed hardwood forests of the Roanoke River basin, North Carolina. Conservation Biology. 8(3): 822-832.

Frazer, D.W., McColl, G., and Powers, R.F. 1990. Soil nitrogen mineralization in a clearcutting chronosequence in a northern California conifer forest. Soil Science Society of America Journal. 54: 1145-1152.

Gendron, F, Messier, C., and Comeau, P.G. 1998. Comparison of various methods for estimating the mean growing season percent photosynthetic photon flux density in forests. Agricultural and Forest Meteorology 92:55-70.

Green, R.N., Trowbridge, R.L., and Klinka, K. 1993. Towards a taxonomica classification of humus forms. Society of American Foresters. Bethesda, MD. Forest Science Monograph 29. 49p.

Griffiths, R P, Caldwell, B.A., Cromack, K. Jr, and Morita, R.Y. 1990. Douglas-fir forest soils colonized by ectomycorrhizal mats. I. Seasonal variation in nitrogen chemistry and nitrogen cycle transformation rates. Canadian Journal of Forest Research 20:211-218.

Griffiths, R.P., Bradshaw, G.A., Marks, B. and Lienkamper, G.W. 1996. Spatial distribution of ectomycorrhizal mats in coniferous forests of the Pacific Northwest, USA. Plant and Soil. 180: 147-158.

Hagerman, S.M., Jones, M.D., Bradfield, G.E., Gillespie, M., and Durall, D.M. 1999. Effects of clear-cut logging on the diversity and persistence of ectomycorrhizae at a subalpine forest. Canadian Journal of Forest Research. 29: 124-134.

Hansen, A.J., Garman, S.L., Lee, P. and Horvath, E. 1993. Do edge effects influence tree growth rates in Douglas-fir plantations? Northwest Science. 67(2): 112-116.

Hart, S.C., Nason, G.E., Myrold, D.D., and Perry, D.A. 1994a. Dynamics of gross nitrogen transformations in an old-growth forest: the carbon connection. Ecology. 75(4): 880-891.

Hart, S.C., Stark, J.M., Davidson, E.A. and Firestone, M.K. 1994b. Nitrogen Mineralization, Immobilization and Nitrification. In Methods of Soil Analysis. Part 2. Microbiological and Biochemical Properties. Soil Science Society of America. Madison, WI. pp 985-1018.

Harvey, A.E., Jurgensen, M.F., and Larsen, M.J. 1980. Clearcut harvesting and ectomycorrhizae: survival of activity on residual roots and influence on a bordering forest stand in western Montana. Canadian Journal of Forest Research. 10: 300-303.

Holland, S.S. 1976. Landforms of British Columbia: A Physiographic Outline. British Columbia Department of Mines and Petroleum Resources. Victoria, BC. Bulletin 48. 138p.

11

Hollstedt, C. and Vyse, A. (eds.). 1997. Sicamous Creek Silvicultural Systems Project: Workshop Proceedings. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997.

Hope, G.D. 1997. Effects of silvicultural systems on soil productivity. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp. 86-91.

Hope, G.D. 1999. Sicamous Creek Silvicultural Systems Project: Effect of silvicultural systems on soil productivity. Unpublished progress report submitted to FRBC.

Hughes, J.W. and Bechtel, D.A. 1997. Effect of distance from the forest edge on regeneration of red spruce and balsam fir in clearcuts. Canadian Journal of Forest Research. 27: 2088-2096.

Hungerford, R.D. and Babbitt, R.E. 1987. Overstory removal and residue treatments affect soil surface, air and soil temperature: implications for seedling survival. Ogden, Utah: USDA Forest Service.

James, J.A. 2000. Effects of timber harvesting systems on nitrogen cycling in a subalpine ecosystem of southern British Columbia. MS Thesis. University of Trier, Department of Physical Geography.

Johnson, C.E., Johnson, A.H., Huntington, T.G., and Siccama, T.G. 1991a. Whole-tree clear-cutting effects on soil horizons and organic matter pools. Soil Science Society of America Journal. 55: 497-502.

Johnson, C.E., Johnson, A.H., and Siccama, T.G. 1991b. Whole-tree clear-cutting effects on exchangeable cations and soil acidity. Soil Science Society of America Journal. 55: 502-508.

Johnson, D.W. 1992. Effects of forest management on soil carbon storage. Water, Air and Soil Pollution. 64: 83-120.

Johnson, K. 1997. Effects of silvicultural treatments on soil foodweb and nitrogen dynamics in englemann spruce-subalpine fir study sites. Unpublished progress report submitted to FRBC.

Johnston, C.A., Pastor, J. and Pinay, G. 1992. Quantitative methods for studying landscape boundaries. In Landscape Boundaries: consequences for biotic diversity and ecological flows. Editors A.J. Hansen and F. di Castri. Springer-Verlag, New York. pp. 107-125.

Kalra, Y.P. and Maynard, D.G. 1991. Methods manual for forest soil and plant analysis. Forestry Canada. Edmonton, Alberta. Information Report NOR-X-319. 116p.

Kapos, V. 1989. Effects of isolation on the water status of forest patches in the Brazilian Amazon. Journal of Tropical Ecology. 5:173-185.

Kaye, J.P. and Hart, S.C. 1997. Competition for nitrogen between plants and soil microorganisms. Trends in Ecology and Evolution. 12(4): 139-143.

Keenan, R.J. and Kimmins, J.P. 1993. The ecological effects of clear-cutting. Environmental Reviews. 1: 121-144.

Keeney, D.R. 1982. Nitrogen – Availability Indices. In Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties, 2nd edition. Editors A.L. Page, R,H, Miller and D.R. Keeney. Soil Science Society of America. Madison, Wisconsin, pp. 711-733.

Killham, K. 1994. Soil Ecology. Cambridge University Press. Cambridge, UK.

Klinka, K., Lavkulich, L., Wang, Q., and Feller, M. 1995. Influence of decaying wood on chemical properties of forest floors and surface mineral soils: a pilot study. Annales des Sciences Forestieres. 52: 523-533.

Knoepp, J.D., and Swank, W.T. 1997. Forest management effects on surface soil carbon and nitrogen. Soil Science Society of America Journal 61: 928-935.

Krause, H. 1998. Forest floor mass and nutrients in two chronosequences of plantations: Jack pine vs. black spruce. Canadian Journal of Soil Science. 78: 77-83.

Kremsater. L.L. 1997. A review of edge effects: theory, evidence and recommendations for managers. Unpublished contract report submitted to MacMillan Bloedel.

Legendre, P., and Fortin, M.-J. 1989. Spatial pattern and ecological analysis. Vegetatio. 80:107-138.

Legendre, P. and Legendre, L. 1998. Numerical Ecology (2nd edition). Elsevier: New York.

Lloyd, D. Angove, K., Hope, G. and Thompson, C. 1990. A guide to site identification and interpretation for the Kamloops Forest Region. British Columbia Ministry of Forests, Land Management Handbook No. 23.

12

Lloyd, D. and Inselberg, A. 1997. Ecosystem mapping for the Sicamous Creek silvicultural systems research site. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp 79-85.

Lloyd, D., Yearsley, K. and Arsenault, A. 1997.Spatial and temporal responses of vegetation to silvicultural treatments in ESSF forests at Sicamous Creek. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp 57-66.

Lowe, J.S. 1993. Canopy closure in young Douglas-fir forests: spatial patterns of understory vegetation, soil moisture and conifer needle litterfall. PhD Dissertation. University of Washington, College of Forest Resources.

Macdonald, N.W., Zak, D.R., and Pregitzer, K.S. 1995. Temperature effects on kinetics of microbial respiration and net nitrogen and sulphur mineralization. Soil Science Society of America Journal. 59: 233-240.

Mahendrappa, M.K., Foster, N.W., Weetman, G.F., and Krause, H.H. 1986. Nutrient cycling and availability in forest soils. Canadian Journal of Soil Science. 66: 547-562.

Matlack, G.R. 1993. Microenvironment variation within and among forest edge sites in the eastern United States. Biological Conservation 66:185-194.

Moore, T.R., Trofymow, J.A., Taylor, B., Prescott, C., Camire, C., Duschene, L., Fyles, J., Kozak, L., Krannabetter, M., Morrison, I., Siltanen, M., Smith, S., Titus, B., Visser, S., Wein, R., and Zoltai, S. 1999. Litter decomposition rates in Canadian forests. Global Change Biology. 5: 75-82.

Murcia, C. 1995. Edge effects in fragmented forests: implications for conservation. Trends in Ecology and Evolution 10:58-62.

Myrold, D.D. 1999. Nitrogen transformations and management interactions in forest soils. In Proceeding of the Pacific Northwest Forest and Rangeland Soil Organism Symposium: Organism Functions and Processes, Management Effects on Organisms and Processes, and Role of Soil Organisms in Restoration, March 17-19, 1998, Corvallis, Oregon. Edited by R.T. Meurisse, W.G. Ypsilantis, and C. Seybold. USDA Forest Service, Portland, Oregon, General Technical Report PNW-GTR-461. pp.106-113.

Nadel, H. 1997. Effects of clearcutting on soil mites and springtails in the subalpine forest of Sicamous Creek. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp 110-120.

Palik, B.J. and Murphy, P.G. 1990. Disturbance versus edge effects in sugar-maple/beech forest fragments. Forest Ecology and Management. 32: 187-202.

Parish, R., Antos, J.A., and Fortin, M.-J. 1999. Stand development in an old-growth subalpine forest in southern interior British Columbia. Canadian Journal of Forest Research. 29: 1347-1356.

Parsons, W.F.J., Knight, D.H., and Miller, S.L. 1994a. Root gap dynamics in lodgepole pine forest: nitrogen transformations in gaps of different size. Ecological Applications 4 (2): 354-362.

Parsons, W.F.J., Miller, S.L., and Knight, D.H. 1994b. Root-gap dynamics in a lodgepole pine forest: ectomycorrhizal and nonmycorrhizal fine root activity after experimental gap formation. Canadian Journal of Forest Research. 24: 1531-1538.

Perry, D.A. 1994. Forest Ecosystems. The Johns Hopkins University Press, Baltimore, MD.

Perry, D.A. 1998. Scientific review of the Sicamous Creek Silvicultural Systems Project. Contract Report to Ministry of Forests, Kamloops, BC. 28p.

Phillips, J.D. 1999. Edge effects in geomorphology. Physical Geography. 20(1): 53-66.

Prescott, C.E. 1997. Effects of clearcutting and alternative silvicultural systems on rates of decomposition and nitrogen mineralization in a coastal montane coniferous forest. Forest Ecology and Management. 95: 253-260.

Prescott, C. and Hope, G. 1997. Sicamous Creek silvicultural systems research trial: litter input, decomposition and nitrogen mineralization. In Sicamous Creek Silvicultural Systems Project: Workshop Proceedings, April 24-25, 1996, Kamloops, British Columbia. Editors C. Hollstedt and A. Vyse. Research Branch, British Columbia Ministry of Forests, Victoria, British Columbia, Working Paper 24/1997. pp.92-100.

Precott, C.E., and Zabek, L.M. 1999. Decomposition and nitrogen mineralization in forests of British Columbia: effects of forest management practices. In Proceeding of the Pacific Northwest Forest and Rangeland Soil Organism Symposium: Organism Functions and Processes, Management Effects on Organisms and Processes, and Role of Soil Organisms in Restoration, March 17-19, 1998, Corvallis, Oregon. Edited by R.T. Meurisse, W.G. Ypsilantis, and C. Seybold. USDA Forest Service, Portland, Oregon, General Technical Report PNW-GTR-461. pp.124-136.

Qian, H., and Klinka, K. 1995. Spatial variability of humus forms in some coastal forest ecosystems of British Columbia. Annales des Sciences Forestieres. 52:653-666.

13

Robertson, G.P., Vitousek, P.M., Matson, P.A., and Tiedje, J.M. 1987. Denitrification in a clearcut loblolly pine (Pinus taeda L.) plantation in the southeastern US. Plant and Soil. 97: 119-129.

Saunders, S.C., Chen, J., Crow, T.R., and Brosofske, K.D. 1998. Hierarchical relationships between landscape structure and temperature in a managed forest. Landscape Ecology. 13:381-395.

Saunders, S.C., Chen, J., Drummer, T.D. and Crow, T.R. 1999. Modeling temperature gradients across edges over time in a managed landscape. Forest Ecology and Management. 117:17-31.

Schmidt, M.G., A.E. Ogden and K.P. Lertzman. 1998. Seasonal comparison of soil temperature and moisture in pits and mounds under vine maps gaps and conifer canopy in a coastal western hemlock forest. Canadian Journal of Soil Science. 78: 291-300.

Schmidt, M.G., Macdonald, S.E., and Rothwell, R.L. 1996. Impacts of harvesting and mechanical site preparation on soil chemical properties of mixed-wood boreal forest sites in Alberta. Canadian Journal of Soil Science. 76: 531-540.

Smethurst, P.J., and Nambiar, E.K.S. 1990a. Distribution of carbon and nutrients and fluxes of mineral nitrogen after clear-felling a Pinus radiata plantation. Canadian Journal of Forest Research. 20: 1490-1497.

Smethurst, P.J., and Nambiar, E.K.S. 1990b. Effects of slash and litter management on fluxes of nitrogen and tree growth in a young Pinus radiata plantation. Canadian Journal of Forest Research. 20: 1498-1507.

Stark, J.M. and Hart S.C. 1997. High rates of nitrification and nitrate turnover in undisturbed coniferous forests. Nature. 385: 61-64.

Stark, J.M. and Hart, S.C. 1999. Effects of disturbance on microbial activity and N-cycling in forest and shrubland ecosystems. In Proceeding of the Pacific Northwest Forest and Rangeland Soil Organism Symposium: Organism Functions and Processes, Management Effects on Organisms and Processes, and Role of Soil Organisms in Restoration, March 17-19, 1998, Corvallis, Oregon. Edited by R.T. Meurisse, W.G. Ypsilantis, and C. Seybold. USDA Forest Service, Portland, Oregon, General Technical Report PNW-GTR-461. pp. 101-105.

Stathers, R.J., Trowbridge, R., Spittlehouse, D.L., Macadam, A. and Kimmins, J.P. 1990. Ecological Principles: Basic Concepts. In Regenerating British Columbia’s Forests. Edited by D.P. Lavender, R. Parish. C.M. Johnson, G. Montgomery, A. Vyse, R.A. Willis and D. Winston. UBC Press. Vancouver. pp. 45-54.

ter Braak, C.J. F. 1998. CANOCO: a program for canonical community ordination by (partial) (detrended) (canonical) correspondence analysis, pca, rda. Version 4.0. Agricultural Mathematics Group. Ministry of Agriculture and Fisheries. Wageningen.

Titus, B.D. and Malcolm, D.C. 1992. Nutrient leaching from the litter layer after clearfelling of sitka spruce stands on peaty gley soils. Forestry. 65(4): 389-416.

Titus, B.D., Roberts, B.A., and Deering, K.W. 1998. Nutrient removals with harvesting and by deep percolation from white birch (Betula papyrifera [Marsh]) sites in central Newfoundland. Canadian Journal of Soil Science. 78: 127-137.

Trettin, C.C., Johnson, D.W., and Todd, D.E. Jr. 1999. Forest nutrient and carbon pools at Walker Branch Watershed: changes during a 21-year period. Soil Science Society of America Journal. 63: 1436-1448.

Vitousek, P. M. 1985. Community turnover and ecosystem nutrient dynamics. In. The Ecology of Natural Disturbance and Patch Dynamics. Edited by S.T.A. Pickett and P.S. White. Academic Press, New York, USA.. pp. 325-333.

Vitousek, P.M., and Andarise, S.W. 1986. Microbial transformations of labeled nitrogen in a clear-cut pine plantation. Oecologia. 68: 601-605.

Vitousek, P.M., and Melillo, J.M. 1979. Nitrate losses from disturbed forests: patterns and mechanisms. . 25 (4): 605-619.

Vyse, A. 1999. Is everything all right up there? A long-term interdisciplinary silvicultural systems project in a high elevation fir-spruce forest at Sicamous Creek, BC. The Forestry Chronicle 75 (3):467-472.

Weetman, G.F., and Webber, B. 1972. The influence of wood harvesting on the nutrient status of two spruce stands. Canadian Journal of Forest Research. 2: 351-369.

Welke, S. and Hope, G. 1999. Sicamous Creek Silvicultural Systems Project: Effect of silvicultural treatments on fine root biomass. Unpublished progress report submitted to FRBC.

Williams-Linera, G, Dominiguez-Gastelu, V. and Garcia-Zurita, M.E. 1998. Microenvironment and floristics of different edges in a fragmented tropical rainforest. Conservation Biology 12 (5):1091-1102.

Zhang, Y., Mitchell, M.J., Driscoll, C.T., and Likens, G.E. 1999. Changes in sulphur constituents in a forested watershed 8 years after whole-tree harvesting. Canadian Journal of Forest Research 29: 356-364.

Zinke, P. 1983. Forest soil properties related to nutrient storage, and their change in the harvest of old-growth, and the regrowth and harvest of second-growth redwoods. Paper read at New Forests for a Changing World: Proceedings of the 1983 Convention of the Society of American Foresters, at Portland, Oregon. pp. 210-215.

14

Zogg, G.P., Zak, D.R., Ringelber, D.B., MacDonald, N.W., Pregitzer, K.S., and White, D.C. 1997. Compositional and functional shifts in microbial communities due to soil warming. Soil Science Society of America Journal. 61: 475-481.

15

Appendix 1 – Proposed research time line (perhaps a bit optimistic!)Year Month Tasks2000 Jan-Apr -prepare thesis proposal,

-hold committee meeting and colloquim, -have methods ready for field season-VM project for Margaret

2000 May -prepare for field sampling (make thermocouples, data sheets, label flags)-general field work in Kamloops for Graeme-help Eva with preliminary analysis of VM spatial data?

2000 June -sicamous site selection and soil sampling -general Kamloops field work

2000 July -field sampling-place out buried bags, extraction of initial n-min samples at SFU and analysis at UBC-temp and moisture measures

2000 Aug -complete field sampling, temp and moisture measures-sample preparation for lab analysis, send to Glyn Rd by end of August?-remove and process buried bags (SFU), send for analysis at UBC

2000 Sept –Dec -sample analysis at Glyn Rd, results by mid-november?, -writing of introduction and detailed methods, -begin analysis of available lab and environmental data-TA for Geog 317

2001 Jan-May -data analysis-prepare figures and tables for paper, -begin writing results -report for Graeme’s FRBC final project report-possible presentations/posters at NWFSC, PEC, WDCAG...-TA or Fellowship?

2000 May-Sept -complete analysis-writing, have draft of paper for submission by early July?-defend Aug/Sept?-work on paper(s)-Fellowship or contract work?

16

Appendix 2 – Preliminary materials and Budget

Sample analysisGlyn Rd*Variable $/sample* total cost (n=511)pH 1.05 540mineralizable N 1.05 540total C&N&S 3.25 1660moisture correction 0.30 153general handling 260

Total MoF Lab 3153

N-min n=750 – includes ~70 blanks and standards for NO3 and NH4

UBC AnalysisNH4 & NO3 5 3750

Grand Total ~$7000*-the Glyn Rd lab is currently undergoing a program review/audit and prices may be going up in the new fiscal year (April) if they have to recover part of the staff salaries

17