The Structure And Productivity Of Relict Stands Of Pitaya (Stenocereus Queretaroensis; Cactaceae), Jalisco, Mexico

THE STRUCTURE AND PRODUCTIVITY OF RELICT STANDS OF PITAYA (STENOCEREUS QUERETAROENSIS; CACTACEAE), JALISCO, MEXICO 1

BRUCE F. BENZ, FRANCISCO SANTANA M., JUDITH CEVALLOS E., ELIZABETH Mtr/qOZ M., JESUS ROSALES A., AND MANUEL ROSALES A.

Bruce F. Benz, Francisco Santana M., Judith Cevallos E., Elizabeth Mufioz M., Jesus Rosales A., and Manuel Rosales A. (Instituto "Manantldn' de Ecologia y Conservacidn de la Biodiverstdad, Centro Umversitarlo de la Costa Sur, Universtdad de Guadalajara, Autldn, Jahsco Mexico C.P. 48901). THE STRUCTURE AND PRODUCTIVITY OF RELICT STANDS OF PITAYA [SrENOCeREUS t2UERETAROENSlS; CACTACEAE] Jahsco, Mexwo. Economw Botany 51(2) 134-143. 1997. Pitaya fruit commercialized in southern Jahsco comes primardy from anthropogenic populations. These populations are associated with archaeological sites dating between 300 B.C. and A.D. 1200. Stand structure and productivity of five anthropogenic stands contrast sharply with that of natural and cultivated stands. Indivzduals from a natural stand have smaller-diameter trunks and canopies and produce less fruit than anthropogenic stands Structure and productivity of one stand may correlate with the assoctated archaeological occupation. Individual producttwty is highly correlated with dtameter of the canopy. Both men and women participate in the harvest and sale of pitaya fruit earnmg the same or as much as three times that paid as wage laborers. Conservation of these stands and the associated archaeological sites would require land purchase and protection but the sale of pttaya fruits could sustain the efforts necessary to protect and manage these populations over the long term.

Estructura y productlvldad de rodales relictos de Pltaya (Stenocereus queretaroensis de Jahsco, Mexico). La mayor parte del fruto commerclahzado de la pttaya en el sur de Jahsco proviene de poblaciones antropog~mcas. Estas poblaciones se asoctan con sittos arqueol6gwos cuyo antzgtiedad es de 300 A.C hasta 1200 D.C. La estructura y productivldad de estas poblaciones contrasten drastwamente con las de poblactones naturales y cultlvadas. Individuos de poblaciones naturales tienen troncos y copas de menor diametro y producen menos fruto que las antropog~mcas. La estructura y productivldad de una poblacton rehcta se corelacionan con la fecha estlmada del sitio arqueoldgico asociado. La producttvldad de los indzviduos se cor- relaczona con el diametro de la copa Mujeres y hombres parttctpan en la cosecha y venta de frutos, ganando al menos el igual o hasta tres veces lo ganado en formas alternativas de trabajo como jornaleros. La conservacidn de estas poblactones y los sitios arqueol6gicos donde se encuentran, requerrers de la compra y protecci6n de las mismas, la venta del fruto de la pttaya podria sostener los esfuerzos necesarlos para protegerlos y manejarlos a largo plazo

Key Words: relict stands, pitaya; Stenocereus queretaroensis; Cactaceae; anthropogemc vegetation; Jahsco.

Near the end of April one inevitably encoun- ters someone selling pitayas in many towns in southern Jalisco and Colima, Mexico. Sale of the fruits of this columnar cactus (Stenocereus queretaroensis (Weber) Buxbaum) occurs following the harvest and sale of guaje [Leucaena esculenta (DC.) Benth.], parota (Enterolobium cyclocarpum (Jacq.) Griseb. seeds, cactus

Received 4 January 1996; accepted 15 December 1996.

[Opuntia spp., Nopalea karwinskiana (Salm- Dick) Schumann] pads, coincides with the fruit harvest of ciruela (Spondias purpurea L.), and precedes the commercialization of nanche [Byr-

sonima crassifolia (L.) HBK] fruits. The local monetary value and social importance of the pitaya harvest has led to the vegetative propaga- tion of the pitaya cactus in orchards (Pimienta and Nobel 1993) though the majority of the local and regional fruit harvest appears to be commercialized from putative natural stands.

Economw Botany 51(2) pp. 134-143. 1997 �9 1997 by The New York Botamcal Garden, Bronx, NY 1045,8 U.S A.

1997] BENZ ET AL.: RELICT STANDS, PITAYA 135

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Fig. 1, Location of the pitaya populations studied in southern Jalisco, Mexico. The Autlan-El Grullo valley is delineated by the road that skirts the surrounding mountains

This research seeks to characterize the structure and productivity of local pitaya stands (known locally as organeras) from which fruit is collected and commercialized. Our objective is to characterize stand structure and the environmental conditions of exploited populations and to document the production and value of fruit harvested by the local people. In the course of our research it became evident that many of these stands occur on archaeological sites. Since 1994, additional populations have been located in the region that conform to the general pattern of high density organeras occurring on archaeological sites.

METHODS AND MATERIALS

THE PLANT AND STAND CHARACTERIZATION

Stenocereus queretaroensis is a columnar cactus distributed across the Mexican states of Co- lima and Jalisco to Guanajuato, Michoacan and Queretaro. The plant attains a height of ten meters or more and branches from the main stem at ground level in cultivated populations or typ- ically at or above 1.5 meters in natural and anthropogenic populations. The plants we studied

reach sexual maturity once they have reached a height of 3 meters, the trunk is 12 centimeters in diameter or has a canopy diameter greater than 1.5 meters.

Six anthropogenic populations of pitaya were located through observation of the collection and commercialization process. Sampling of four stands (Monte Alto, El Corcovado, Rn. Lu- isa and E1 Limoncillo) used ten randomly located 1000 m 2 plots. The population at Las Urracas was sampled using nine 1000 m 2 plots. The huerto (orchard) of don Felipe, was mapped as one continuous irregular area 85 by 55 meters. The natural population was characterized in the course of establishing a one hectare permanent forest plot in the municipality of Tuxcacuesco, Jalisco. Two of these stands are located outside of the Autl~a-E1 Grullo valley (Fig. 1).

Stands were characterized at the end of the flowering period to ensure that individuals could be distinguished from the sympatric pitaya ci- marrdn [ Pachycereus pecten-aboriginum (Englm.) Britt. & Rose]. Height, diameter at breast height (dbh), average canopy diameter and fruit number were recorded for individuals exceeding 1.3

136 ECONOMIC BOTANY [VOL 51

meters tall. All individuals of pitaya and pitaya cimarr6n in each plot, including those less than 1.3 m tall, were mapped to the nearest 0.5 meter Cartesian coordinates using meter tapes. Height was measured with an Haga Pistol, dbh with a diameter tape and canopy diameter with a meter tape. Fruit number was counted using binocu- lars.

Site histories were recorded in interviews with local collectors, site managers, and land owners, taking note of whether the site was also used for agriculture or cattle grazing. Local collectors and vendors were interviewed about the amount of time they invest in harvesting, processing and sale, their approximate earnings and about economic alternatives to collection and sale of pitaya fruit. Evidence of land use prac- tices that might have occurred prior to the mem- ory of local informants was also recorded. Ele- ments of the surrounding vegetation were iden- tified in the course of characterizing the pitaya stands to describe the associated plant community.

ANALYTICAL METHODS

The observed association of high density populations of pitayas with prehispanic occupation sites suggested that perhaps the vegetation associated with the pitaya populations might also be relictual. Our hypothesis was that the vegetation associated with the relict stands might also reflect human manipulation. This was tested using a chi-squared test that compares the number of useful tree species at these sites to the number of useful species documented in the undisturbed one-hectare tract of TDE We also hypothesized that structural and productive differences between relict populations might be due to past human manipulation. Analyses were conducted to point out morphological differences that may have resulted from human selection. Pitaya populations were compared using one-way analysis of variance and the Scheffe procedure of the multiple range test for individual intersite com- parisons on variables ranked across populations (ties were averaged) to determine whether differences exist in fruit production, height, dbh and canopy area. Scheffe's procedure was cho- sen because it is a conservative procedure for demonstrating pair-wise differences between groups. These variables were averaged across 1000 m E quadrats and again transformed to ranks and compared using rank density as a covariate

to determine whether variation in production and structure might be explained by density. Step- wise linear regression has been used to determine which of the structural variables is the best predictor of productivity and how much of the variation in fruit production can be explained from stand structure. The null hypothesis in comparing stand structure was that no difference existed between populations. Analyses and graphics were obtained using SPSS and SYS- TAT (SPSS 1990; Wilkinson 1990a,b).

STUDY SITES

Monte Alto, as it is known locally, is seven hectares in extension located approximately ten kilometers north of the city of Juchitlfin along the highway to Tecolotl(m at ca. 1150 meters above sea level (Fig. 1). The entire site is littered with prehispanic cultural material that occurs at low density (less than 100 sherds meter-2). The ceramics are similar to types defining the Cof- radia Phase in the Autlan valley (Classic period ca. 600 to 900 A.D.; Kelly 1945). Two and perhaps more small mounds, five meters in diameter and one to two meters high, are located at the center of the pitaya population. The agricultural parcels making up the site are cultivated and grazed annually. Vegetation associated with the pttayas is dominated by short-statured thorny shrubs of TDF (Table 1).

The huerto of don Felipe is located in a resi- dential area of AutlS_n at an altitude of 940 m above sea level along the southern margin of the Cuajinque river. No surface indications of prehispanic architecture were observed but cultural material assignable to the Postclassic period Au- tl~in Phase (ca. 900 to 1200 A.D., Kelly 1945) litters the surface. Sherd density is low. The site is grazed year around, has a fenced perimeter and is sparsely vegetated. Tins organera is a small remnant which has been managed by aug- menting the spontaneous population with vegetative cuttings of regional varieties.

E1 Limoncillo (our designation) is located approximately 2 km south of Autl~a and 1 km west of the road to Casimiro Castillo. This population occurs on a very steep and rocky, east- facing slope above 940 meters. Cultural material assignable to the Late Preclassic Tuxcacuesco complex (ca. 300 a.c. to A.O. 100; Benz and Laitner Benz n.d.; Kelly 1949) occurs on the level areas to the east and south and co-occurs with Classic and Postclassic period ceramics

1997] B E N Z E T A L . : R E L I C T S T A N D S , P I T A Y A 137

T A B L E 1. TREES AND SHRUBS OCCURRING IN ASSOCIATION WITH RELICT STANDS OF STENOCEREUSQUER- ETAROENSIS IN SOUTHERN JALISCO, M E X I C O (* INDICATES SPECIES IS ONE OF THE TEN MOST COMMON,

+ INDICATES ITS PRESENCE WAS RECORDED AT THE SITE, BLANK INDICATES IT WAS NOT SEEN AT THE

SITE, a INDICATES THE SPECIES IS UTILIZED). A LIST OF ASSOCIATED SPECIES IS NOT INCLUDED FOR THE

TUXCACUESCO POPULATION BECAUSE IT NUMBERS MORE THAN 2 5 0 SPECIES OR FOR THE HUERTA OF DON

FELIPE BECAUSE IT HAS NO OTHER TREES OR SHRUBS. APPROXIMATELY 6 0 PERCENT OF THE TREE AND

SHRUB SPECIES OCCURRING IN THE TROPICAL DECIDUOUS FOREST AT THE SITE NEAR TUXCACUESCO ARE

UTILIZED BY LOCAL PEASANTS.

Monte Rlncon Las Species Alto Corcov Lmsa Llmonc Urracas

Acacia macllenta R o s e a * * * * *

Acacia farnestana (L.) W l l l d a * * * * ,

Acacia rlparla H B . K . +

Acacia cochhcantha H u m b & B o n p l . ex W d l d . a * * *

Aeschynomene amorphotdes (S. W a t s o n ) R o s e e x B . L R o b . +

Agonandra racemosa ( D C ) S t a n d l / +

Albtzia tomentosa ( M i c h e h ) S t and l . a +

Amphipterygtum adstrlngens S c h l e c h t . a +

Bursera fagarotdes ( H B . K . ) E n g l a + +

Bursera kerbert Engl . ~ +

Bursera grandlfoha ( S c h l e c h t . ) E n g l . a + +

Bursera penlcdlata (DC) E n g l ? + + +

Caesalpmea cacalaco H u m b & B o n p l ~ +

Casearta corymbosa H . B K ? *

Celtts zguanaea ( J a c q ) Sa rg . a * + * *

Celtls caudata P l a n c h o n a *

Celtts pallida T o r r e y + +

Cephalocereus alensis ( W e b e r ) B n t t . & R o s e +

Ceiba aescuhfoha ( H B . K . ) B n t . & B a k e r ~ + + +

Colubrma triflora B r o g n . ex S w e e t + +

Coursetia glandulosa A. G r a y a * * *

Gyrocarpus jatrophlfolius D o m i n a + +

Hehocarpus terebmthinaceus ( D C ) H o c h r . a +

Hintoma lattflora (Sess6 & M o c e x D C ) B u l l o c k ~ + +

lrestne casstnttformis S c h a u e r * +

Jatropha mcvaughit D e h g a n & W e b s t e r ~ + *

Lysiloma acapulcense ( K u n t h ) B e n t h a . +

Lystloma microphyllum B e n t h . ~ + + +

Malplghta mexwana Andr . Juss . *

Mimosa benthamnt M a c b r . *

Montanoa tomentosa C e r v . a +

Opuntla fuhgmosa Gri f f . a * * *

Pachycereus pecten-abortginum (Eng l . ) B n t t & R o s e a * * * * *

Ptsonta aculeata L~ + Pithecellobtum dulce (Rox . ) B e n t h a *

Prosopis laevtgata (Wl l ld . ) M . C . J o h n s t a * * * * *

Senna atomaria (L.) I r w i n & B a r n e b y a + + +

Shaefferla pdosa Stand l . * * +

Slderoxylon cartdagineum ( C r o n q . ) P e n n i n g t o n ~ *

Spondias purpurea L? * Thevetta ovata (Cav . ) D C ~ +

Vttex molhs H B K. f o r m a lltlsii M o l d e n k e ~ +

Zanthoxylum fagara ( L ) C. S a r g e n t +

Ziziphus meMcana Rose" * + +

138 ECONOMIC BOTANY [VOL. 51

(Cofrad/a and Aut l~ Phases; Kelly 1949) on the slopes in and around the columnar cacti. Sherd density on the flats is moderate (more than 100 sherds meter -2) but low on the slopes. These slopes have been grazed for many years but have not been cultivated. The margins of the organera and the adjacent slopes are inhabited by elements of TDF (Table 1).

Las Urracas is located approximately 6.5 km south-west of Aut l~ on a northwest-facing slope. This population inhabits a moderate rocky slope at an elevation of 900 meters. Cultural material assignable to the Tuxcacuesco Phase is restricted to the level areas to the northwest. Sherd density is low. The site is used principally for grazing but has not been tilled recently. The organera is also forested by TDF (Table 1).

Lagunillas (our designation) is located at 890 meters on an east-facing slope on the opposite side of the ridge from Las Urracas. This population is confined to the sloping margins of an agricultural field on the upslope side of a major irrigation canal. It has been planted yearly since the 1930s and cultivated with a tractor for the past 20 years. The surrounding slopes are vegetated by TDF (Table 1). Moderate densities of cultural material assignable to the Tuxcacuesco Phase occur in association with four mounds ar- ranged around a small circular plaza at the south end of the pitaya population.

Corcovado (our designation) is located on a moderate south-facing slope two kilometers southwest of the town of the same name along the north side of the highway to Autl~in. This is the largest (>200 ha) but most dispersed population studied. A low density of Autlan and Cof- radia Phase cultural materiales were noted on the surface. Local inhabitants and the landowner indicate that small mounds previously present at the site have been obliterated. This site has been cultivated annually for nearly thirty years and was devoted to cattle grazing before that time. A small part of this population includes young immature individuals that were planted and protected by the landowner.

The natural pitaya population was characterized in the process of establishing a 1 hectare permanent plot in undisturbed TDE This population is located on a ridge at 950 meters 3.5 km southwest of Tuxcacuesco along the road to Camichin. The associated vegetation includes more than 70 tree species [e.g., Pachycereus pecten-aboriginum, Euphorbia tanquahuete Ses-

s6 & MOC., Bursera grandifolia (Schlecht.) Engl., Cedrela salvadorensis Standl.] whose stature is equal to or slightly greater than that of the pitaya population. The pitayas are not a dominant element of the forest at this site.

RESULTS ASSOCIATED VEGETATION

A test of the hypothesis that the pitaya stands are anthropogenic was conducted by comparing relative proportions of useful plants from the lists of species associated with the relict stands and the natural pitaya population near Tuxca- cuesco. Approximately 77 percent (34 of 44) of the tree species occurring in association with the relict pitaya populations are reported as useful (Table 1). Fifty-seven percent (45 of 79) of the species occurring in one hectare of undisturbed Deciduous Tropical Forest have been described as useful by local informants (Benz et al. un- published data). A significantly greater number of useful species (• = 4.8; P < 0.05) occur in association with relict stands suggesting that the plant communities associated with anthropogenic populations of pitaya may be anthropogenic as well.

STAND STRUCTURE

The pitaya population from Tuxcacuesco is smaller except in height and is less productive than all other populations (Tables 2 and 3). It is probable that pitayas growing under natural conditions do not attain the size or productivity of anthropogenic populations. Such differences may be due to the less favorable environmental conditions under which the population in the Tuxcacuesco site exists, viz., the surrounding vegetation is denser, the landform and substrate is less fertile or more well-drained, or may result from selection for more productive individuals in the case of the anthropogenic populations. It is also possible that the Tuxcacuesco population has been established for less time than the anthropogenic populations.

The small orchard population of don Felipe is comparable to the population at Corcovado in terms of height and to Mt. Alto and Lagunillas in canopy diameter (Table 2). The greater diameter trunks observed in don Felipe's orchard might be attributed to the fact that vegetatively propagated individuals branch closer to the ground and have greater diameters closer to the ground (see Pimienta-Barrios and Nobel 1994:


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TABLE 4 . REGRESSION EQUATIONS FOR EACH SITE TO PREDICT FRUIT PRODUCTION BASED FRUIT-BEARING

INDIVIDUALS. FRUIT PRODUCTION AT TUXCACUESCO COULD NOT BE PREDICTED FROM VEGETATIVE CHAR-

ACTERISTICS.

Mt . A l t o F r u i t n o = - 192 .5 + ( C a n o p y d i a m e t e r ) 90 .7 + ( D B H ) 4 0 r 2 = 0 . 5 4 P < 0 001

C o r c o v a d o F r u i t n o = - 4 1 5 6 + ( C a n o p y d m m e t e r ) 2 1 4 9 r 2 = 0 4 2 P < 0 001

L a g u n i l l a s F r m t n o = - 3 5 7 7 + ( C a n o p y d m m e t e r ) 64 .2 + ( H e i g h t ) 4 3 7 r 2 = 0 . 4 6 P < 0 001

L i m o n c d l o F r m t n o = - 2 2 7 + ( C a n o p y d m m e t e r ) 4 2 7 r 2 = 0 . 3 0 P < 0 . 0 0 1

L a s U r r a c a s F r m t n o = - 7 6 0 + ( C a n o p y d m m e t e r ) 72 .8 r 2 = 0 .43 P < 0 001

d o n Fe l i pe F r u i t n o = - 3 0 7 + ( D B H ) 3 4 r 2 = 0 .19 P < 0 .05

Fig. 2). On average these pitayas produce approximately the same amount of fruit as the population at El Limoncillo which is located only two kilometers to the south (Table 3).

The five remaining relict populations are vari- able in terms of stand structure and fruit production. The population at Corcovado is the most distinctive having the lowest density of plants per 0.1 ha 2 and the shortest and most productive individuals. The Corcovado population also has significantly greater dbh than other populations if only fruiting individuals are considered (Tables 2 and 3).

At the other extreme, the greater density population at E1 Limoncillo has significantly fewer fruits per individual than the other populations, is composed of smaller diameter individuals than all populations except Las Urracas and is comprised of shorter individuals than those at Lagunillas and Las Urracas (Tables 2 and 3). Variation in stand structure and fruit production of these populations demonstrates considerable overlap between E1 Limoncillo and the other populations though individuals at Lagunillas and Las Urracas are taller than those at other sites.

While these five populations exhibit considerable variation in stand structure, low regeneration is one general trend they share. The number of individuals smaller than 20 cm dbh ranges from 2 to 30 percent and the number less than 10 cm dbh comprises less than 5 percent except at Corcovado and E1 Limoncillo. The abundance of small-dbh individuals at Corcovado is due to recent planting by the land owner. Only the population at El Limoncillo appears to exhibit significant regeneration. If this apparently low per- centage is indicative of the regenerating capacity of these populations and is not a natural char- acteristic of the species (Peters' [1994] Type II or HI; see also Steenbergh and Lowe 1977), the future of these populations appears threatened.

Relatively higher regeneraUon at El Limoncillo may result because access is restricted to collectors and the fact that the area is not cultivated and is lightly grazed.

No clear association is evident between the apparent antiquity of these populations (as estimated from archaeological surface indications) and stand characteristics except at Corcovado. Individuals at Corcovado are shorter and more productive than in other populations, two traits that are advantageous to humans. This population is associated with archaeological horizons (Classic-Postclassic) when population density appears to have been at Its highest in the Autlan-E1 Grullo Valley (Kelly 1945). We sus- pect that these short but highly productive individuals are the result of human selection for greater and more easily harvested fruit production. Future study of this population will allow us to test this hypothesis.

PRODUCTIVITY

We hypothesized that part of the observed variation in fruit production might be explained by the density of individuals occurring within 0.1 ha. Density does explain a sigmficant portion of the variation in pitaya size and production when individuals of all size categories are included (Table 2) but explains little of the variation m pltaya size or productivity among populations when only fruit-bearing individuals are considered (Table 3).

Average canopy diameter is the best predictor of production in fruiting individuals from anthropogenic populations (Table 4). Fruit production in the Mt. Alto and Lagunillas populations was explained further by variables other than canopy diameter. Production of more than 100 fruits per individual occurs when canopy diameter exceeds 2 meters. Maximum production occurs m individuals hawng canopies greater than


5 meters. Presumably, greater canopy diameter reflects the greater number of branches and surface area for fruit production. Unfortunately we did not quantify branch number. On average, approximately 40 percent of the variation in fruit production can be explained by variation in vegetative characteristics of these individuals. If canopy diameter and dbh accurately reflect the age structure of these populations, then one possible explanation for the relatively low productivity of the population at E1 Limoncillo is that it is somewhat younger than the others. Other factors may explain the differences in productivity among sites. Further study of the effects of density of the surrounding vegetation (especially that of the pltaya cimarr6n), the efficacy of pol- linator(s) and substrate fertility on fruit production at each site will shed light on the observed differences.

SOCIAL AND ECONOMIC IMPORTANCE OF THE PITAYA

Interviews with pitaya collectors indicate that extraction and commercialization are important regional economic alternatives both to land owners and landless peasants. Of the seven populations described here, five are subject to commercial exploitation. The E1 Corcovado population is currently harvested and commercialized by the landowner who estimated commercial value of this population to exceed N$75 per day during the period of peak production (monetary equivalents when these data were collected was approximately N$3.2:$1 US). The population at E1 Limoncillo is located on ejido grazing lands where access to commercial exploitation of pitaya fruit is restricted. Collectors at E1 Limon- cillo pay a nominal fee (in 1993 it was N$250 per year) to harvest in an area of one to two hectares. Collection at Mt. Alto, Lagunillas and Las Urracas is not restricted.

The fruit produced at Corcovado is harvested by the landowner and sold by his wife. Fruit is harvested by both men and women at the other sites and only a few of these collectors have land-tenure fights. Both men and women collect, remove the spines from the fruit and offer it for sale to passersby at Mt. Alto, although there may be a gender division of labor among family members with collection assumed by one person and processing and sale assumed by another. Which sex dedicates time to harvesting or commercialization depends upon alternative liveli-

hood opportunities and the family demands placed on each individual's time. On one occa- sion, 11 of 15 collectors at Mt. Alto were women, while on numerous occasions at Las Urracas and E1 Limoncillo, all were men. None of these collectors had land tenure fights. At these and other sites collectors may sell their daily harvest to intermediaries who resell pitaya on the coast where it is not locally available or to the larger cities where demand is greater. Purchase price by an intermediary is usually less than half that offered to the consumer.

The economic reward for pitaya collection and sale appears to be adequate for landless peasants, especially those who have few other economic alternatives, Based upon interviews with thirty collectors and vendors, price per fruit varies during the six to nine week harvest period. All collectors indicated that the first week or two of the fruiting period and the last week were times of relatively low fruit availability. Most persons interviewed devote time to harvest and sale of pitayas only during the period of peak production one or two weeks after it first be- comes available and before production diminish- es during the last week. During the first weeks, price per fruit is 50% higher than during the four or more weeks of peak production. Price may again decrease by as much as 20% during the last week(s) of production. Daily individual earnings vary accordingly reaching their highest point, N$ 59 per day, during the first few weeks of fruit availability, decreasing slightly during the following three to six weeks to N$ 51 per day, and dropping to N$ 21 per day during the last week. These daily earnings are greater than the most frequently cited alternative sources of income which paid N$15 to 25 per day in other agricultural activities.

We initially believed that collection intensity was a major determinant of the apparent low regeneration of these populations. Based on harvesting patterns of collectors at Mt. Alto, we estimate that under economically-motivated conditions, as much as 80% of all the fruit produced by the population is collected for sale. This would remove a significant proportion of seed for regeneration. This estimate does not contem- plate the number of immature fruits that are in- advertently knocked down or destroyed in the harvesting process. Obviously, fruit harvesting is an important factor affecting regeneration. This in combination with cultivation of the soil


and both intensive and extensive cattle grazing appear to pose a threat to these anthropogenic populations.

DISCUSSION AND CONCLUSIONS

The occurrence of high density pitaya populations on archaeological sites suggests that they are of precolumbian origin. However, this asser- tion should not be misinterpreted to suggest that the individuals themselves are ancient. While there is no published method for accurately ag- ing these columnar cacti, local informants suggest that a large individual is productive for perhaps 40 to 60 years, a period of time equalling two human generations. While this estimate may be considerable for an orchard crop, even if this estimate were doubled to take juvenile and se- nescent periods into consideration, the life span would not be sufficient to extend across the 600 years needed to link the most recently occupied archaeological sites--at E1 Limoncillo and the huerto of don Felipe--with the present day. It seems more likely that existing populations are descended from cultivated, encouraged, or tol- erated ancestors established during the pre-Co- lumbian era. Many elements of the managed prehispanic vegetation of the area have survived to the present day (Kelly 1945; Laitner Benz and Benz 1994).

The generally high harvesting rate and small seedling pool, except in areas protected by fenc- es, such as Corcovado and don Felipe's huerta, leads us to believe that fruit collection and alternative forms of land use place these populations in a very tenuous situation. It seems probable that simultaneous and alternative forms of land use further reduce the regenerative potential of these populations. Livestock grazing and cultivation of the soil could be expected to jeop- ardize the establishment of seedlings as well as endanger the shallow root systems of older individuals.

While many of the biological, physical, and social aspects of these productive populations await further research, their immediate protection should be considered. Demands placed on land are increasing at an alarming rate and the traditional post-Columbian methods of land use appear to pose the greatest threats to these populations. Conservation of these sites as living archaeological/ethnobotamcal museums (Wilkes 1993) is one logical alternative. Cultivation of the pitaya is a viable form of land use in other

T A B L E 5 . A N N U A L P R O D U C T I O N ESTIMATES FOR

THE A N T H R O P O G E N I C PITAYA P O P U L A T I O N S FROM

S O U T H E R N J A L I S C O .

Annual production Site tons hectare -~

Huerta de Sayula, Jal.* 5.0 (17 max) Huerta de Dn. Fehpe 0.5 Las Urracas 1.1 El Llmoncdlo 1.6 Rinc6n de Luisa 2.1 Corcovado 2.3 Monte Alto 2.4

* Ptmlenta-Bamos y Nobel (1994) The huerta from Sayula described by Ptmlenta and Noble has approximately 600 plants/ha, individuals 25 years old produce between 44-98 frmts per mthwdual Their esamates are based on an average fruit weight of 122 gms per fruit Estimated fruit weight from our sites Is 100 gms, total number of fruits produced per hectare at each site is presented m Table 3

parts of Jalisco and Colima (Pimienta-Barrios and Nobel 1994; S. Lemus pers. comm.) and these relict populations approximately equal the annual production of recently planted varieties without additional start-up costs (Table 5). Set- ting these areas aside to protect the archaeological as well as biological patrimony seems jus- tified. Combining tourism with agricultural production should be examined as a way of con- serving in situ these cultural, economic and ecological resources.

ACKNOWLEDGMENTS This research was supported by the Blodwerslty Support Program,

Earthwatch Volunteers and the Umverslty of Guadalajam H Iltls, L S~tnchez-Velazquez, E Plmlenta and two anonymous reviewers com- mented on an earher draft This paper was written while the first author was on sabbatical at the Botamcal Research Institute of Texas Thanks for support and encouragment are due to S Sohmar, B Llpscomb, J Plpoly and the entire BRIT staff for their hospltahty and enthusiasm S Dalh and S Burkett drafted Fig 1

LITERATURE CITED

Benz, Bruce F., and Karen Laitner Benz. n.d Re- laclones culturales de la cerfimlca de Tuxcacuesco y Morett vistas desde El Colomo, Jalisco Memoria del IV Coloqmo de Occldentalistas. ORSTOM- Universidad de Guadalajara, Guadalajara. (in press)

Bravo-Hollis, Helia, and Hernando Sdnehez-Mejor- ada R. 1991. Las cact~ceas de M6xlco. Volumes I-III. UNAM, Mexico.

Kelly, Isabel. 1945. The archaeology of the Auddn- Tuxcacuesco area of Jalisco. I. The Autl~in Zone. Umverslty of California Press: Berkeley

�9 1949. The archaeology of the Autlfin-Tux- cacuesco area of Jalisco II: The Tuxcacuesco-Za- potitlfin Zone. University of California Press: Berkeley.


Laitner Benz, Karen, and Bruce F. Benz. 1994 Las condiclones culturales y ambientales en la Reserva de la Blosfera Sierra de Manantl~in en tiempo de la Conquista: Una perspectlva de los documentos et- nohist6ncos secundarios Estudios del Hombre 1: 15-46. Umversidad de Guadalajara.

Peters, Charles M. 1994 Sustainable harvest of non- timber plant resources in tropical moist forest: An ecological primer Washington, D.C.: Biodiversity Support Program-WWE

Hmienta-Barrios, Eulogio, and Park S. Nobel. 1994. Pltaya (Stenocereus spp., Cactaceae): An ancient and modern fruit crop of Mexico. Economic Botany 48:76-83.

Steenbergh, Warren F., and Charles H. Lowe.

1977. Ecology of the Saguaro: II. Reproduction, germination, establishment, growth and survival of the young plant. National Park Service Monograph Series No. 8 U.S. Government Printing Office, Washington, D C

SPSS. 1990. Statistical package for the social sci- ences. SPSS, Inc., Chicago.

Wilkes, H. Garrison. 1993. E1 teosmte en M6xlco como modelo para la conservacl6n in situ: Un reto. Pages 257-270 in B. E Benz, (Comp.), Biologfa, ecologfa y conservaci6n del g6nero Zea. Universl- dad de Guadalajara, Guadalajara, Jalisco, Mexico.

Wilkinson, Leland. 1990. SYSTAT: The system for statlstacs. SYSTAT, Inc., Evanston, IL.

�9 1990. SYGRAPH: The system for graphics SYSTAT, Inc., Evanston, IL

BOOK REVIEW

Local Knowledge and Agricultural Decision Mak- ing in the Philippines. Virginia D. Nazarea-San- doval 1995. Cornell University Press, Sage House, 512 E. State Street, Ithaca, NY 14850 xm + 226 pp. (hardcover). $49.95 ISBN 0-8014-2801-7

This book presents a study of the interaction between mental models and agricultural decision making of a small sample of inhabitants of a community in the Philippines, and how this interacuon is shaped by socioeconomic stratification and gender differences. The mental models (cogmzed models) refer to maps of the community, folk taxonomles of plants and arthropods, and the evaluatmn of major land use options. Agricul- tural decision making refers to the allocation of land, time and food. These decisions occur in the context of an operational reality--the hiophysical factors and the socioeconomic condmons that this people face.

The topic and the goal of the book are ambitious. Nazarea-Sandoval offers an stamulatmg and competent ethnography of the village studied, presenting a good historical perspecnve on the changes in land tenure, the use of resources and the economic acuvmes that have occurred there. She does an m-depth study of 12 households, representing three socioeconomic strata (high, middle and low), from whom she elicits the cognized models, and describes their operational reality

I found the techniques used to elicit the mental models entacing. Unfortunately, her treatment of the operational reality and its interacUon with the cognized models is weak. First, the characterization and presen- tation of the operational reality are poor. For example, although a key topic is the allocation of time, she does not present a complete calendar of economic activmes throughout the year. Therefore, one has little idea of

the rhythms and seasonal variation of the system, par- tlcularly of the labor bottlenecks and how these are addressed. Second, quantitative data are poorly presented and difficult to follow. Third, she makes asser- tions that go beyond her data. For example, to explain why some households keep on producing nee even though there are less demanding, and possibly more lucrative economic activiues, she says that the farmers feel the obligation to do so Yet, she does not present data that actually shows that such alternative activities are indeed superior m terms of labor demand, profit or risk. Fourth, there are inconsistencies m the interpre- tation of the relationship between the cogmzed models and the operational reality. For example, she notes that m the maps of the community, middle-ranking households do not distinguish fish ponds and rice fields, and lump these categories into "wetlands," m contrasts with the other two groups She argues that this indicates a lower salience for an innovative strategy (fish ponds), and associates it with middle class conserva- tism However, when one examines the data on land allocation, the middle-ranking households have as much land devoted to fish ponds as the higher status ones.

Although the book has some good points, it falls to deliver on the central part of the study, Le., dealing with the relationship between indigenous knowledge and decision making. I would recommend consulting this book only to those interested in the techmques to elicit indigenous knowledge.

MAURICIO R. BELLON IRRI (INTERNATIONAL RICE RESEARCH INSTITUTE)

PHILIPPINES RESEARCH CENTER LOS BAfilOS, LAGUNA

PHILIPPINES

Documents

The Structure And Productivity Of Relict Stands Of Pitaya (Stenocereus Queretaroensis; Cactaceae), Jalisco, Mexico