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La riqueza de especies de plantas vasculares epfitas que viven sobre Catura y variedades de caf hibrido en San Luis, Costa Rica
Species richness of epiphytic vascular plants living on Catura and Hbrido coffee varieties in San Lus, Costa Rica
Coffea arabica is a widespread crop, existing both in monocultures as a cultivated variety of tree and in mixed organic farms in numerous varieties. This study takes place on an organic farm where the varieties host diverse species of vascular epiphytes. This study compares the species richness of vascular epiphytes on trunks and stumps of the cultivated variety known locally as caturra and also several closely related traditional varieties collectively known locally as hbrido.
Results show that exposure to sunlight was significantly more influential than the type of coffee variety in determining the average richness per tree. However, the caturra cultivar thrives under full sunlight, whereas hbrido cultivars do best with shade, possibly allowing caturra to be better
hosts for vascular epiphytes. Other studies state epiphyte species richness increases with tree size. Tree size was not a variable in this study, but this would be a good idea for further study.
Coffea arabica es un cultivo generalizado, existiendo tanto en el monocultivo como una variedad cultivada de rboles y en fincas orgnicas mezcladas en numerosas variedades. Este estudio se lleva a cabo en una finca orgnica donde las variedades albergan diversas especies de epifitas vasculares. Este estudio compara la riqueza de especies de epifitas vasculares en troncos y tocones de la variedad cultivada conocida localmente como Caturra y tambin varias variedades tradicionales estrechamente relacionados conocidos localmente como hibrido. Los resultados muestran que la exposicin a la luz solar fue significativamente ms influyente que el tipo de variedad del caf en determinar el porcentaje de riqueza por rbol. Sin embargo, la variedad Caturra prospera bajo plena luz del sol, mientras que los cultivos hbridos hacen mejor con sombra, posiblemente permitiendo a caturra a ser mejores anfitriones para las epifitas vasculares. Otros estudios indican que la riqueza de especies de epifitas aumenta con el tamao del rbol. El tamao del rbol no era una variable en este estudio, pero esta sera una buena idea para su posterior estudio.
Text in English.
Costa Rica--Puntarenas--Monteverde Zone--San Luis
Costa Rica--Puntarenas--Zona de Monteverde--San Luis
Tropical Ecology Summer 2010
Ecologa Tropical Verano 2010
t Monteverde Institute : Tropical Ecology
Species richness of epiphytic vascular plants living on Catura and Hbrido coffee varieties in San Lus, Costa Rica Trevor Biggs Department of Biology ABSTRACT Coffea arabica is a widespread crop, existing both in monocultures as a cultivated variety o f tree and in mixed organic farms in numerous varieties. This study takes place on an organic farm where the varieties host diverse species of vascular epiphytes. This study compares the species richness of vascular epiphytes on trunks and stumps of the cultivated variety known locally as caturra and also several closely related traditional varieties collectively known locally as hbrido Results show that exposure to sunlight was significantly more influential than the type of coffee variety in determin ing the average richness per tree. However, the caturra cultivar thrives under full sunlight, whereas hbrido cultivars do best with shade, possibly allowing caturra to be better hosts for vascular epiphytes. Other studies state epiphyte species richness increases with tree size. Tree size was not a variable in this study, but this would be a good idea for further study. INTRODUCTION As tropical forest is being destroyed to make space for agriculture, conservation biologists are especially concerned ab out subsequent massive species extinctions and losses of biodiversity. For this reason it is helpful to know what species can adapt to a developed area, an organic farm in upper region of San Luis, Costa Rica. This farm primarily consisted of coffee tree s ( Coffea spp. ). There are nearly seven million tons of coffee produced annually worldwide from 100,000 km^2 of land. At least forty nine of the fifty four coffee producing countries in the world exist partially or entirely within the Intertropical Conver gence Zone (ITCZ) (International Coffee Organization (ICO)). Eighty five percent of terrestrial species live in this region. With such a large abundance of growing coffee in a region of such high species richness, it can be useful to know how species res pond to coffee farms. In this study I observe species richness of vascular epiphytes on the coffee trees. Species richness refers to how many different species exist, irrelevant of their population sizes. Epiphytes are plants that grow up along other pla nts for their support. They absorb water from the air or from pockets of water on the surface of the host tree. It is estimated that 20,000 to 25,000 species of vascular epiphytes exist worldwide (Zotz and Hietz 2001). They make up approximately ten per et al. 2002). Epiphytes may serve a crucial role as good for the rich invertebrate and fish fauna of the littoral zone of lakes and rivers (Cattaneo 1983). They also exert a moderating effect on microclimatic condition s of forest canopy, therefore protecting small animals, especially arthropods, whose fitness is rigidly limited by microclimatic conditions (Stuntz, Simon, and Zotz 2002). Through studies like this and similar others,
hopefully increasing knowledge of vas cular epiphyte host tree relationships can help to preserve their diversity and their important ecological roles. Specifically, this study compares and contrasts epiphytic species richness on different genetic varieties of Coffea arabica One such variety is locally known as Caturra. Caturra is known for being cultivated by people, doing best in full sun, producing more fruit, being shorter, and having a shorter lifespan (Perfecto et al 1996). The other genetic varieties collectively fall under the grou p called Hbrido. The Hbrido varieties are known for doing best in shady areas, being taller, and having a longer lifespan (Perfecto et al 1996). Because Caturra and Hbrido prefer different levels of sunlight, they tend to be found in different locati ons (personal observation). This study conducts two observational designs. One is in order to see if vascular epiphytes prefer either Caturra or Hbrido simply based on any difference in their composition. The other is to see if vascular epiphytes prefe r either variety in practice, based on where the trees actually grow. MATERIALS AND METHODS Study Site Data for this study were collected at the organic farm of the Leitn family in upper San Luis, Costa Rica. The elevation is approximately 1,100 m. The farm stands on a region previously considered a premontane moist forest by the Holdridge Life Zones. A premontane moist forest typically experiences one to four meters of annual precipitation and a Potential Evapotranspiration (PET) ratio of 0.5 to 1.0. The PET ratio is the rate of water loss to the rate of water gain of a system, such as an ecosystem. The farmers do not add synthetic agrochemicals, such as certain fertilizers, pesticides, and herbicides, to the farm. Some areas of the farm are dominat ed by a single crop, and others are very mixed. Some areas are shaded by canopy trees and others not. Comparison 1: Old stumps of Caturra and Hbrido The numbers of different species of vascular epiphytes on large stumps of Caturra and Hbrido tree were m easured. These stumps were found in areas where they were more abundant than other trees. Larger stumps were sought for selection. Each stump was located within two meters of a stump of the other variety (together making a pair), so the only notable dif ferences between them were tree variety, size, shape, and age. However, all stumps used were at least twenty years old (Eugenio Vargas Leitn, personal communication), so there was some consistency. Pairs with similar numbers of cuts and similar size wer e preferred for observation because this could alter the surface area of the stump. The diameter, height, and number of cuts made were measured for each stump. Diameter measurements were converted to circumference, and along with height measurements it c ould be used to estimate the total surface area of the stump. Vascular epiphytes were identified by visible morphological traits (e.g., roots, flowers). If the category of a vascular epiphyte species was known, the species was identified as a member of th at category with a letter to distinguish it from others of the same category (e.g., Orchid B). If the species could not be identified, it was identified for future reference by category of unkowns (e.g., Unkown E). No letter was used for more than one sp ecies of the same category.
A photograph was taken of each species so to ensure proper identification if the species were later on another sample. The sample size was twenty. Comparison 2: Old trunks of Caturra and Hbrido In this case the numbers of dif ferent species of vascular epiphytes on the trunks of the two coffee varieties were recorded. Only adult trunks were used. Epiphytes were not recorded if they were not attached to the trunk below eye level. Diameter of the base of each trunk was measure d and so was the height at which the trunk began growth (in the case that it grew out of a previous cut) because these have an effect on the total surface area available for epiphytes. Trunks were selected from regions where they were the most abundant tre e type. Those which grew directly from the ground and those which appeared fully grown were preferred for selection. Vascular epiphytes were identified by morphological traits. A photograph was taken of each species so to ensure proper identification if the species were later on another sample. The sample size was twenty. RESULTS Comparison 1 Average species richness of Caturra and Hbrido stumps were not significantly different (Mann Whitney U test, P = 0.91, n = 20; Figure 1). The twenty samples of Caturra stumps collectively hosted twenty one different species, while the twenty Hbrido stumps hosted twenty two total. There were fourteen species qualitative index of for community similarity of C = 0.65 (i.e. 65% of species are in common and a value of 1.00 would represent entirely similar communities). Comparison 2 Average species richness of Caturra an Hbrido trunks were significantly different (Mann Whitney U test, P = 0.027, n = 20; Figure 1). The twenty samples of Caturra trunks collectively hosted sixteen species, while the twenty Hbrido trunks hosted seven total. There were six species common to both trunk varieties. These values yield a value for the community similarit y of C = 0.52 (i.e. 52% of species are in common). This means that vascular epiphyte species richness varied more between different trunks varieties than between different stump varieties. Other observations A Kruskal Wallis comparing all four categories (Caturra stumps, Hbrido stumps, Caturra trunks, and Hbrido trunks) shows that there is significant difference in average vascular epiphyte species richness between every group except between Caturra stumps and Hbrido stumps (H = 28.6, P < 0.0001, n = 20 ). Stumps observed all had relatively short trunks growing from them because they had been cut back. For this reason, trunks had fewer branches, stems, and leaves shading them. It also appeared that more sun reached stumps than trunks in general because branches only grew from the trunks, so there were more leaves shading the trunks. The vascular epiphytes observed on the most individuals (from any of the four groups) were Fern A (51 counts), Fern B (31), Unkown O (24), and
Peperomia A (23). Unkown O) wa s a small weedy like plant that also grew frequently from the ground. Figure 1. Species richness of vascular epiphytes averages 3.75 species per tree in both varieties of stumps. Caturra trunks average 2.5 species per tree, and Hbrido trunks average 1.25 species per tree. DISCUSSION Since all stumps were old (at least twenty years old) and pairs were sought for evenness in size, shape and microclimate, possibly the only notable variable was stump variety. This and the fact tha t trunk of the different varieties generally grew in different locations suggest that the cause of significant variation in vascular epiphytic species richness on trunks between the two tree variations was due to a change in microclimate. Because trunks i n groups of their own variety were sought for selection they were probably in locations with preferable levels of sunlight, so there must have been variation in microclimate between Caturra and Hbrido trunks. Varying microclimate may have caused there to be less overlap in species between trunk varieties (C = 0.52), opposed to more overlap with the
controlled microclimate of stump varieties (C = 0.65). These results suggest that environmental conditions other than substrate are more important to epiphyte s than substrate, at least in within the scope of coffee plants as the substrate, possibly explaining the difference in species richness of vascular epiphytes between Caturra and Hbrido trunks. There was also a significant difference in species richness b etween trunks of either variety and stumps of either variety. Since Caturra trunks were exposed to sun, the reason they still did not host as much species richness as stumps may due to the stumps being more exposed to this sun. Stumps were sought for sel ection partially on a basis for being wider. Also, stumps, being at the base of the tree where there are no branches, especially since branches were cut away in the process of making the bases to be stumps, are likely not to experience as much self shadin g by the leaves and branches as the trunks, which are surrounded by leaves and branches. It is also possible that only measuring trunks up to eye level eliminated measurement of potentially more suitable substrate for epiphytes. Higher areas of the trunk have fewer and often smaller branches above them, possibly allowing for more sun exposure. It has been observed that the number of epiphytic species and their biomass was closely related to tree size, but altitude was a stronger factor, and tree species had little to no influence (Hietz, Hietz Seifert, and Ursula 1995). This study does not observe different altitudes, but a future study may take altitude into consideration with coffee trees. What this observation of altitude significance has in common w ith this study is that it is an environmental condition. Observation 1 of this study agrees with the Hietz, Hietz Seifert and Ursula 1995 study that tree species made minimal difference to epiphyte species richness. For these reasons it seems epiphytes a re more concerned with environmental conditions than quality of substrate. This seems to be in accordance with the fact that epiphytes use trees to position themselves closer to the sun and not for food directly as parasites would. However, some correlat ive investigations have evidence that epiphytes vary in abundance between different potential hosts (Callaway et al 2002). Further investigation may clarify specific behind epiphyte preferences and how much variance between hosts can be significant in ep iphyte selection. Most likely this depends varies for each epiphyte host combination. Also, further study could test the importance of varying substrate for parasitic plants (those which use a host plant as a food source although they do not kill the hos t). My study did not look at epiphytes on branches. Epiphytic growth is more abundant on larger thicker branches and branches more perpendicular to the trunk (Ingram and Nadkarni 1993). Further study could investigate more variables of branches to disco ver if there is another valuable source for diverse species of vascular epiphytes. Possibly the end of branches have more due to more sun or less due to younger age. Results could give farmers or others a better idea about how they should prune if they a re concerning species richness. ACKNOWLEDGEMENTS I would like to thank all of the chefs who kept our CIEE group well fed and functioning, Jos
good example, Pab lo Allen for his good humor and brainpower, Raquel Martnez for her tranquil fun spirit, Kathy Rockwell for organizing so much adventuring and for an awesome birthday cake and hug, and last but not least, Alan and Karen Masters for being exceptional teache rs, role models, and friends. LITERATURE CITED Historical Data, International Coffee Organization http://www.ico.org/new_historical.asp PDF for 2000 to date for Total production, (Augst 7, 2010). ZOT Z, G. AND P. HIETZ. 2001. The physiological ecology of vascular epiphytes: current knowledge, open questions. Journal of Experimental Botany, Vol. 52, No. 364, pp. 2067 2078. CALLAWAY, R. M., K. P. REINHART, G. W. MOORE, D. J. MOORE, AND S. C. PENNINGS. 20 02. Epiphyte host preferences and host traits mechanisms for species specific interactions. Population Ecology. Vol. 132, pp. 221 230. CATTANEO A. 1983. Grazing on epiphytes. American Society of Limnology and Oceanography, Inc. Vol. 28, No. 4, pp 124 132. STUNTZ, S., U. SIMON, AND G ZOTZ. 2002. Rainforest air conditioning: the moderating influence of epiphytes on the microclimate in tropical tree crowns. International Journal of Biometeorology. Vol. 46, pp. 53 59. PERFECTO, I., R. A. RICE, R. GREENBERG, AND M. E. VAN DER VOORT. 1996. Shade Coffee: A Disappearing Refuge for Biodiversity. BioScience Vol. 46, No. 8, 598 608. HIETZ, P., HIETZ SEIFERT, AND URSULA. 1995. Composition and ecology of vascular epiphyte communities along an altitudinal gradient in cen tral Veracruz, Mexico. Journal of Vegetation Science, Vol. 6, 487 498. INGRAM, S. W. AND N. M. NADKARNI. 1993. Xomposition and Distribution of Epiphytic Organic Matter in a Neotropical Cloud Forest, Costa Rica. BIOTROPICA, Vol. 25, No. 4, pp. 370 383.