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Effects of tree buttresses on nutrient availability and macroinvertebrate species richness

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Title:
Effects of tree buttresses on nutrient availability and macroinvertebrate species richness
Translated Title:
Efectos de los contrafuertes del árbol en la disponibilidad de nutrientes y la riqueza de especies de macroinvertebrados ( )
Physical Description:
Book
Language:
English
Creator:
Mack, Alyson P

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Subjects / Keywords:
Soils composition   ( lcsh )
Invertebrates   ( lcsh )
Costa Rica--Puntarenas--Monteverde Zone--Monteverde   ( lcsh )
Composición del suelo
Invertebrados
Costa Rica--Puntarenas--Zona de Monteverde--Monteverde
Tropical Ecology Fall 2003
Ecología Tropical Otoño 2003
Genre:
Reports   ( lcsh )
Reports

Notes

Abstract:
This study tested the hypothesis that buttress microhabitats collect more leaf litter and have greater macroinvertebrate species richness, thereby increasing the leaf decomposition rate and providing more nutrientrich soil for the tree. Leaf litter deposition and decomposition rates, soil fertility (pH, N, P, |K), and macroinvertebrate species richness (S, Smarg) were compared between microhabitats in buttressed and nonbuttressed trees and open areas in the lower montane cloud forest of Monteverde, Costa Rica. Results showed no significant difference between microhabitat types for soil pH levels (Kruskall-Wallis test, H= 3.188), soil N (Kruskall-Wallis test, H= 3.388), soil P (Kruskall-Wallis test, H= 6.215), soil K (Kruskall-Wallis test, H= 4.304), deposition rates (Kruskall-Wallis test, H= 3.599), or decomposition rates (Kruskall-Wallis test, H= 1.746). There was no significant difference in species richness (S) between buttressed trees and non-buttressed trees (Kruskall-Wallis post hoc, q = 1.72) or between non-buttressed trees and open areas (Kruskall-Wallis post hoc, q = 2.64). However, the difference in S between buttressed trees and open areas was significant (Kruskall- Wallis post hoc, q = 4.36). Results suggest that increased leaf litter biomass in buttresses is due to their functioning as collection cavities. Similarities in soil fertility and decomposition rates may be attributed to edaphic and leaf litter heterogeneity within microhabitats. It is apparent that buttress microhabitats are unique in structure, microclimate, and macroinvertebrate community complexity; however results of this study are inconclusive as to whether buttresses actually provide the tree with more nutrients. The role of buttresses in improving local soil quality needs to be further examined, with more consideration given to spatial heterogeneity within microhabitats.
Abstract:
Este estudio probo la hipótesis de que el contrafuerte de los microhábitats recogen más basura de hojas y tienen una mayor riqueza de especies de macroinvertebrados, aumentando de este modo la tasa de descomposición de las hojas y el suelo rico proporciona más nutrientes para el árbol. La deposición de hojarasca y las tasas de descomposición, la fertilidad del suelo (pH, N, P, K, y la riqueza de especies de macroinvertebrados (S, Smarg) fueron comparados entre los microhábitats en los arboles con contrafuertes y sin contrafuertes y áreas abiertas en el bosque nuboso montano bajo de Monteverde, Costa Rica. Los resultados no mostraron diferencias significativas entre los tipos de microhábitats para los niveles de pH del suelo (prueba de Kruskall Wallis, H = 3. 188), suelos N (prueba de Kruskal Wallis, H = 3.388), el suelo P ( prueba de Kruskall Wallis, H = 6.215), el suelo K (la prueba de Kruskall Wallis, H = 4.304), las tasas de deposición (prueba de Kruskall Wallis, H = 3.599), o las tasas de descomposición (prueba de Kruskall Wallis, H = 1.746). No hubo diferencia significativa en la riqueza de especies (S) entre los árboles con contrafuertes y no contrafuertes (Kruskall Wallis post hoc, q = 1.72) o entre árboles no reforzadas y áreas abiertas (Kruskall Wallis post hoc, q = 2.64). Sin embargo, la diferencia en S entre los árboles con contrafuertes y áreas abiertas fue significativa (Kruskall Wallis post hoc, q = 4.36). Los resultados sugieren que el aumento de desechos de biomasa foliar en contrafuertes se debe a su funcionamiento como cavidades de colección. Las similitudes en la fertilidad del suelo y las tasas de descomposición pueden ser atribuidas a la heterogeneidad edáfica y la basura foliar dentro de los microhábitats. Es evidente que los microhábitats con contrafuertes son únicos en la estructura, en el microclima, y en la complejidad de la comunidad de macroinvertebrados, sin embargo los resultados de este estudio no son decisivos en cuanto a si los contrafuertes proporcionan verdaderamente al árbol con más alimentos nutritivos. El papel de los contrafuertes en la mejora de la calidad local del suelo debe de examinarse más a fondo, con más consideración dada la heterogeneidad espacial dentro de los microhábitats.
Language:
Text in English.
General Note:
Digitized by MVI

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usfldc doi - M39-00438
usfldc handle - m39.438
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This study tested the hypothesis that buttress microhabitats collect more leaf litter and have greater
macroinvertebrate species richness, thereby increasing the leaf decomposition rate and providing more nutrientrich
soil for the tree. Leaf litter deposition and decomposition rates, soil fertility (pH, [N], [P], |K]), and
macroinvertebrate species richness (S, Smarg) were compared between microhabitats in buttressed and nonbuttressed
trees and open areas in the lower montane cloud forest of Monteverde, Costa Rica. Results showed
no significant difference between microhabitat types for soil pH levels (Kruskall-Wallis test, H= 3.188), soil
[N] (Kruskall-Wallis test, H= 3.388), soil [P] (Kruskall-Wallis test, H= 6.215), soil [K] (Kruskall-Wallis test,
H= 4.304), deposition rates (Kruskall-Wallis test, H= 3.599), or decomposition rates (Kruskall-Wallis test, H=
1.746). There was no significant difference in species richness (S) between buttressed trees and non-buttressed
trees (Kruskall-Wallis post hoc, q = 1.72) or between non-buttressed trees and open areas (Kruskall-Wallis post
hoc, q = 2.64). However, the difference in S between buttressed trees and open areas was significant (Kruskall-
Wallis post hoc, q = 4.36). Results suggest that increased leaf litter biomass in buttresses is due to their
functioning as collection cavities. Similarities in soil fertility and decomposition rates may be attributed to
edaphic and leaf litter heterogeneity within microhabitats. It is apparent that buttress microhabitats are unique in
structure, microclimate, and macroinvertebrate community complexity; however results of this study are
inconclusive as to whether buttresses actually provide the tree with more nutrients. The role of buttresses in
improving local soil quality needs to be further examined, with more consideration given to spatial heterogeneity
within microhabitats.
Este estudio probo la hiptesis de que el contrafuerte de los microhbitats recogen ms basura de hojas y tienen una mayor riqueza de especies de macroinvertebrados, aumentando de este modo la tasa de descomposicin de las hojas y el suelo rico proporciona ms nutrientes para el rbol. La deposicin de hojarasca y las tasas de descomposicin, la fertilidad del suelo (pH, [N], [P], [K], y la riqueza de especies de macroinvertebrados (S, Smarg) fueron comparados entre los microhbitats en los arboles con contrafuertes y sin contrafuertes y reas abiertas en el bosque nuboso montano bajo de Monteverde, Costa Rica. Los resultados no mostraron diferencias significativas entre los tipos de microhbitats para los niveles de pH del suelo (prueba de Kruskall Wallis, H = 3. 188), suelos [N] (prueba de Kruskal Wallis, H = 3.388), el suelo [P] ( prueba de Kruskall Wallis, H = 6.215), el suelo [K] (la prueba de Kruskall Wallis, H = 4.304), las tasas de deposicin (prueba de Kruskall Wallis, H = 3.599), o las tasas de descomposicin (prueba de Kruskall Wallis, H = 1.746). No hubo diferencia significativa en la riqueza de especies (S) entre los rboles con contrafuertes y no contrafuertes (Kruskall Wallis post hoc, q = 1.72) o entre rboles no reforzadas y reas abiertas (Kruskall Wallis post hoc, q = 2.64). Sin embargo, la diferencia en S entre los rboles con contrafuertes y reas abiertas fue significativa (Kruskall Wallis post hoc, q = 4.36). Los resultados sugieren que el aumento de desechos de biomasa foliar en contrafuertes se debe a su funcionamiento como cavidades de coleccin. Las similitudes en la fertilidad del suelo y las tasas de descomposicin pueden ser atribuidas a la heterogeneidad edfica y la basura foliar dentro de los microhbitats. Es evidente que los microhbitats con contrafuertes son nicos en la estructura, en el microclima, y en la complejidad de la comunidad de macroinvertebrados, sin embargo los resultados de este estudio no son decisivos en cuanto a si los contrafuertes proporcionan verdaderamente al rbol con ms alimentos nutritivos. El papel de los contrafuertes en la mejora de la calidad local del suelo debe de examinarse ms a fondo, con ms consideracin dada la heterogeneidad espacial dentro de los microhbitats.
546
Text in English.
650
Soils composition
Invertebrates
Costa Rica--Puntarenas--Monteverde Zone--Monteverde
4
Composicin del suelo
Invertebrados
Costa Rica--Puntarenas--Zona de Monteverde--Monteverde
653
Tropical Ecology Fall 2003
Ecologa Tropical Otoo 2003
655
Reports
720
MVI
773
t Monteverde Institute : Tropical Ecology
856
u http://digital.lib.usf.edu/?m39.438



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Effects of tree buttresses on nutrient availability and macroinvertebrate species richness Alyson P. Mack Department of Biology, Gordon College ___________________________________________________________________________ ABSTRACT This study tested the hypothesis that buttress microhabitats collect more leaf litter and have greater macroinvertebrate species richness, thereby increasing the leaf decomposition rate and providing more nutrient rich soil for the tree. Leaf litter deposition and decomposition rates, soil fertility (pH, [N], [P], |K] ), and macroinver tebrate species richness (S, Smarg ) were compared between microhabitats in buttressed and non buttressed trees and open areas in the lower montane cloud forest of Monteverde, Costa Rica. Results showed no significant difference between microhabitat types for soil pH levels ( Kruskall Wallis test, H= 3.188), soil [N] (Kruskal l Wallis test, H= 3.388), soil [P] (Kruskal l Wallis test H= 6.215), soil [K] (Kruskal l Wallis test, H= 4.304), deposition rates (Kruskal l Wallis test, H= 3.599), or decomposition rates (Kruskal l Wallis test, H= 1.746). There was no significant difference in species richness (S) between buttressed trees and non buttressed trees (Kruskal l Wallis post hoc, q = 1.72) or between non buttressed trees and open areas (Kruskal l Wallis post hoc, q = 2.64). However, the difference in S between buttressed trees and open areas was significant (Kruskal l Wallis post hoc, q = 4.36). Results suggest that increased leaf litter biomass in buttresses is due to their functioning as collection cavities. Similarities in soil fertility and decomposition rates may be attributed to edaphic and leaf litter heterogeneity within microhabita ts. It is apparent that buttress microhabitats are unique in structure, microclimate, and macroinvertebrate community complexity; however results of this study are inconclusive as to whether buttresses actually provide the tree with more nutrients. The rol e of buttresses in improving local soil quality needs to be further examined, with more consideration given to spatial heterogeneity within microhabitats. RESUMEN Este estudio prob la hip tesis que sostiene reunir de micro hbitats m s basura de hoja y tiene riqueza m s grande de especie de macroinvertebrate, con lo cual aumen tando la tasa de la descomposici n de hoja y proporcionando ms t ierra rica de alimento nutritivo para el rbol Deposicin de basura de hoja y tasas de descomposicin la fecundidad de tierra (pH, [N] [ P], [ K] ), y riqueza de especie de macroinvertebrate (S, S marg ) fueron comparados entre micro hbitats en so stuvo y no sostuvo rboles y abre r eas en el bosque m s bajo de nube de montane de Monteverde, Costa Rica. Los resultados mostraron no diferencia significativa entre de tipo micro hbitats para niveles de pH de tierra (la prueba de Kruskall Wallis, H = 3.188), la tierra [N] (la prueba de Kruskal l Wallis, H = 3.388), la tierra [P] (la prueba de Kruskal l Wallis, H = 6.215), la tierra [K] (la prueba de Kruskal l Wallis, H = 4.304), las tasas de deposicin (la prueba de Kruskal l Wallis, H = 3.599), ni las tasas de la descomposicin (la prueba de Kruskal l Wallis, H = 1.746). No haba la diferencia significativa en la riqueza ( S) de la especie entre sostuvo rboles y no sostuvo rboles (Kruskall W allis anuncia este, q=1.72) o entre no sostuvo rboles y abre reas (Kruskal l Wallis anuncia este, q = 2.64). Si n embargo, la di ferencia en el S entre sostuvo rboles y abre reas eran significativo (Kruskal l Wallis anuncia e ste, q = 4.36). Los resultados sugieren

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que la biomasa aumentada de basur a de hoja en contrafuertes est debido a su funcionar como cavidades d e coleccin Las similitudes en la fecundidad de tierra y tasas de descomposicin pueden ser atribuidas al edaphic y la heterogeneidad de la basura de la hoja dent ro de micro hbitats Es aparente que ese micro hbitats de contr afuerte es extraordinario en la estructura, en el microclima, y en la complejidad de la comunidad de macroinvertebrate, sin embargo los resultados de este estudio son no decisivos en cuanto a si contrafuertes proporcionan verdaderamente el r bol con m s alimentos nutritivos. El papel de contrafuertes a mejorar la calidad local de tierra necesita ser an m s examinado, con m s consideraci n dada a la heterogeneidad espacial dentro de micro hbitats INTRODUCTION The adaptive role of buttressing in tropical canopy trees is an issue of longstanding debate among scientists that has prompted the formulation of several hypotheses. Buttresses may be a response to mechanical strain and tension (Richards 1996 ; Smith 1972) a defense against nearby plant competitors or woody vines (Black 1979), a physical support (Richards 1996; Hartshorn 1983; Smith 1972), or a means to improve local soil quality. The latter "nutrient hypothesis", which is the focus of this study, proposes that buttress cavities improve the collection of organic debris and moisture. Buttress microhabitats would support a richer detritivore macroinvertebrate community, increasing decomposition rates and thus increasing the amount of nutrients available to th e tree. Nitrogen, Phosphorous, and Potassium are elements that most frequently limit plan t production (Brady and Weil 1996 ), while soil pH affects the plants' ability to absorb these nutrients from the soil (Killham 1994). Nitrogen is important for the gro wth and development of roots as well as the uptake of other nutrients (Taize and Zeiger 1991). Phosphorous reduces the amount of water loss from stomata and increases the roots' ability to absorb water. Potassium aids in photosynthesis, N fixation, and roo t growth. Buttressing, which may enhance the availability of these nutrients through increased decomposition rates, would therefore be advantageous in nutrient poor tropical soils (Jordan 1985). Soil fertility is improved by increased rates of leaf litter deposition and decomposition. Buttresses may aid in the accumulation of excess leaf litter. Nguyen (1996 ) showed that the bowl shaped microhabitats formed between tension buttresses and the trunk base contained greater leaf litter abundance in comparison t o down slope buttress microhabitats. Decomposition rates increase with increased moisture, temperature (Jordan 1985), and detritivore community diversity, as leaf litter macroinvertebrates, along with bacteria and fungi, are vital for the transformation of dead organic matter to essen tial soil nutrients. Nguyen (1996 ) showed that buttresses are significantly higher in moisture content. A diverse macroinvertebrate community may be more attracted to buttresses as they decrease exposure to sunlight and wind (Marks 1995). In previous studies, positive correlations have been found between arthropod in vertebrate abundance, richness, and diversity and environmental factors such as higher moisture levels (LeDoux 1988; Frith and Frith 1990), greater depth of leaf litter (Seidler 1992; Lee 1993; Marks 1995), and leaf litter heterogeneity (Lee 1993). These a re all conditions that

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are likely to appear in buttresses, therefore creating a suitable microhabitat for a more diverse macroinvertebrate community and increasing rates of decomposition. The purpose of this study is to determine whether buttresses increas e the nutrients available to the tree. This will be determined by examining differences in soil fertility (pH, [N], [P], [K]), deposition and decomposition rate, and invertebrate species richness between buttressed and non buttressed trees. I propose that buttressed trees will have increased soil fertility, greater deposition and decomposition rate, and greater macroinvertebrate species richness than non buttressed trees. METHODS Study Site This s tudy was conducted at 1550 1650 m secondary forest of the Pacific slope near the Estacin de Biol gica de Monteverde, Costa Rica (10 18' N, 84 48' W), from October 18, 2003 to November 18, 2003 (the end of the rainy season). It typically rained in the afternoon and often throughout the night for the duration of this study. Sampling Procedure and Analysis Ten buttressed trees and ten non buttressed trees were chosen without regard to species. Ten open areas served as control sites to compare the effects of being near a buttressed or non buttressed tree. Soil fertility. Soil samples were collected from 18 sites (six samples per microhabitat type) by first clearing away organic matter and then removing the top layer of soil (0 5 cm deep). Soil pH, [N], [P], and [K] were measured using a LaMotte soil analysis kit. A Kruskal Wallis test was run to determine whether there was a difference in soil fertility between microhabitat types. Decomposition rate. A mesh bag contai ning 100 g of dry, heterogeneous leaf litter was secured at each of the 30 study sites on 10/23/03. After 23 days, the bags were collected and the mass of the leaf litter was measured again, yielding decomposition rates. A Kruskal Wallis test was run to de termine whether there was a difference in decomposition rate between microhabitat types. Deposition rate. An open topped, wire mesh box was secured in each of the 30 study sites on 10/29/03. The mass of fallen leaf litter was measured in the field on 11/3/ 03 11 /8/03, and 11/14/03. Boxes were emptied each time to prevent overflow. The total mass of litter deposited per study site during the 17 day period was used to calculate deposition rates. A Kruskal Wallis test was run to determine whether there was a d ifference in deposition rate between microhabitat types. Macroinvertebrate species richness. A leaf litter sa mple was collected from each of 1 8 study sites (six samples per microhabitat type). Macroinvertebrates were separated from leaf litter samples using Berlese funnels for 24 hours. The species richness (S) was counted for each sample, and the number of individuals (N) was counted for three

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samples of each microhabitat type. The Margalef index of species richness (S marg ) was calculated for those nine samples. A Kruskal Wallis test was used to determine whether there was a difference in S between microhabitat types. Kruskal Wallis post hoc tests were then run to determine whether there were differences in S between individual pairs of microhabitats. RESULTS Soil Fertility There was no significant difference between microhabitat types for pH levels (Kruskal Wallis test, H= 3.188), [N] (Kruskal Wallis test, H= 3.388), [P] (Kruskal Wallis test, H= 6.215), or [K] (Kruskal Wallis test, H= 4.304). [P] was nearing sign ificance, with mean values (in l bs/acre) of 58.3 35.0 and 108.3 for buttressed trees, non buttressed trees, and open areas, respectively (Table 1). Deposition Rate There was no significa nt difference between microhabitat types for deposition rates (Kruskal Wallis test, H= 3.599). Mean values between microhabitat types are reported in Table 1. Decomposition Rate There was no significant difference between microhabitat types for decompositi on rates (Kruskal Wallis test, H= 1.746). Mean values between microhabitat types are reported in Table 1. Macroinvertebrate Species Richness (S) There was a significant difference between microhabitat types for S (Kruskal Wallis test, H= 9.680). Further analysis showed a significant difference in S between buttressed trees and open areas (Kruskal Wallis post hoc, q= 4.36, Fig. 1). There was no significant difference in S between buttressed trees and non buttressed trees (Kruskal Wallis post hoc, q=1.72), but while there was also no significant difference in S between non buttressed trees and open areas (Kruskal Wallis post hoc, q= 2.64), the difference was approaching significance. The S marg values for buttressed trees appear to be highe r than non buttressed trees, and significantly higher than open areas, which would correspond with the results for S, however, no statistical analyses could be performed due to small sample size (Fig. 2).

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DISCUSSION It was thought that buttressed trees would have increased soil fertility, a greater deposition and decomposition rate, and greater macroinvertebrate species richness than non buttressed trees. However, the results of this study showed no significant difference between microhabitat types for a ny of the parameters studied. A significant difference in macroinvertebrate species richness was found between buttressed trees and open areas, with a difference nearing significance between non buttressed trees and open areas. Soil Fertility In a previous study, no correlation was found between buttressed Quercus spp. and increased [N], [P], and [K] or more beneficial pH levels (Platt 2003). It was suggested that the similar nutrient levels between buttressed trees, non buttressed trees, and the control ar e due to a significant amount of root nutrient absorption. Similarly, in this study, as no trees were present near the control, nutrient depletion was probably not due to tree root absorption. Therefore, it is possible that excess nutrients available to th e buttressed and non buttressed trees were more rapidly absorbed, accounting for the similarities in soil fertility among microhabitats (Denslow 1987). This may explain why [P] was nearing significance (p= 0.0580), with buttressed and non buttressed trees having much lower average P levels than open areas (Table 1). As P is often a limiting factor in plant growth, it is likely that the trees were absorbing the available P, accounting for higher levels in the open areas. The extreme heterogeneity of leaf lit ter in tropical forests may also cause edaphic heterogeneity within microhabitats (Marks 1995; Maheswaran and Gunatilleke 1988), attributing the similarities in soil fertility to spatial scale and sample size. Deposition Rate Similarities in leaf deposition rate between microhabitats show that the cavities of buttresses do not have higher rates of leaf fall than the bases of non buttressed trees or open areas. However, Nguyen (1996) showed that buttresses are significantly high er in leaf litter depths, indicating that buttresses actually do function as collection cavities. Marks (1995) showed that increased leaf litter biomass was found below trees with epiphytes, which may have been influential in changing deposition rates betw een microhabitats. Also, the control open areas were in more disturbed secondary forest patches that contained more understory growth, more pioneer species, and smaller trees, a characteristic of treefall gaps. These areas typically have more wind and larg er, faster growing leaves (Denslow 1987), which may have caused more leaf litter of larger size to be blown into the collection boxes, rather than falling in directly. Due to the steep slopes of the study sites, the bases of non buttressed trees on the ups lope side may have accumulated leaf litter in the same way that buttressed trees do. However, it seems more likely that there is more movement of leaf litter near non buttressed trees

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and open areas, so further studies should consider deposition rates at d ifferent spatial and temporal scales. Macroinvertebrate Species Richness (S) The results of this study showed a significant difference in macroinvertebrate species richness between buttressed trees and open areas. The difference in macroinvertebrate specie s richness between non buttressed trees and open areas was approaching significance, while the difference between buttressed and non buttressed trees was not. Spatial heterogeneity within microhabitats may account for these differences. Microhabitats are e xtremely complex, heterogeneous, and dynamic. Small scale differences in structure, moisture level and orientation of habitats has major effects on invertebrate diversity, with communities being influenced by factors such as epiphytes, depth of leaf litter nutrient availability, and species immigration (Marks 1995). Increased leaf litter biomass increases litter heterogeneity and creates unique niches for organisms to inhabit. Also, as different types of leaves have different decomposition patterns (Mahesw aran and Gunatilleke 1988) greater accumulations of leaf litter of different leaf types would cause nutrients to be released at different times in different forms, thereby supporting a more diverse invertebrate community (Ezcurra and Becerra 1987). Further studies should examine macroinvertebrate species richness and the effects of heterogeneity within microhabitats to determine the benefits of buttressing in trees. Leaf Decomposition There was no significant difference between microhabitats f or leaf decomposition, which may be a reflection of climatic conditions or macroinvertebrate communities. Climatic conditions within microhabitat types probably vary greatly, although they were not directly tested in this study. Previous studies, however, have shown that buttresses contain greater moisture levels than other microhabitats (Nguyen 1996 ). This study did show a significant increase in macroinvertebrate species richness for buttressed trees, but it did not appear to affect the decomposition rate Decomposition rates vary for different leaf types (Maheswaran and Gunatilleke 1988) which may account for similarities in leaf decomposition rates. Differences in leaf litter heterogeneity may have a large impact on the patterns and time scale of decompo sition within microhabitats. Future studies may control for species in leaf litter to determine differences in decomposition rates based on buttress microhabitat conditions and macroinvertebrate communities alone. Concluding Remarks The "nutrient hypothesi s" for buttressing explored in this study has not been rejected, nor has it been fully supported. Buttress microhabitats are damper, appear to function as collecting cavities for leaf litter, and harbor more species rich macroinvertebrate communities. Howe ver, whether these microhabitat conditions increase decomposition

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rate and improve local soil fertility remains to be determined. Future studies should focus on differences in edaphic and leaf litter heterogeneity within buttress microhabitats. It seems li kely that the complexity of buttress formation in tropical trees is due to a combination of factors and will not be fully explained by any single hypothesis ACKNOWLEDGMENTS I would like to thank Karen Masters, Alan Masters, Carmen Rojas, Andrew Rodstrom, Andres Vaughn, and Matt Gasner for helping me with this project, from the initial brainstorming down to the little nitpicky details. Thanks to Joe Northrup for his help with the Berlese funnels. Thanks to Michelle Murphy, Catherine Ross, and Joel Stonedale for keeping me entertained in the lower lab. Thanks especially to the Estacin Biologica de Monteverde for providing me with a place to do this study. _________________________________________________________________________________________ LITERATURE CI TED Black, H. L., and K. T. Harpe. 1979. The adaptive value of buttresses to tropical trees; additional hypotheses. Biotropica 11:240. Brady, N.C. and R. R. Weil. 1996. The Nature and Properties of Soils. Prentice Hall, New Jersey. Denslow, J. 1987. Tropical rainforest gaps and tree species diversity. Ann. Rev. Ecol. Syst. 18: 431 451. Ezcurra, E. and J. Becerra 1987. Experimental decomposition of litter from the Tamaulipan Cloud Forest A comparison of four simple models. Biotropica 19(4):290 296. Frith, D. and C, Frith. 1990. Seasonality of litter invertebrate populations in an Australian upland tropical rainforest. Biotropica22 (2): 181 190. Hartshorn, G S. 1983. Plants. In D. H. Janz en (ed.). Costa Rican Natural History. Univers ity of Chicago Press, Chicago. Jordan, D. F. 1985. Nutrient Cycling in Tropical Ecosystems. John Wiley and Sons, New York. Killham 1994. Soil Ecology. Cambridge University Press, Cambridge. LeDoux, C.M. 1988. Exploring the importance of moisture to invertebrate abundance in leaf litter. The Evergreen State College Winter Program Abroad in Monteverde, Costa Rica. Lee.T. 1993. Leaf litter depth and insect fauna. UCEAP, Monteverde, Costa Rica. Maheswaran, J. and I.A.U.N. Gunatilleke. 1988. Litter deco mposition in a lowland rain forest and a deforested area in Sri Lanka. Biotropica 20 (2): 90 99. Marks, D. 1995. Epiphytic litter fall and leaf litter invertebrate diversity. UCEAP/spring, Monteverde, Costa Rica. Nguyen, N. T. 1996. Comparing invertebrat e leaf litter habitats within tension and compression buttresses of trees on cloud forest inclines. CIEE/summer, Monteverde, Costa Rica Platt. M. 2003. Advantageous development of buttresses displayed in Quercus spp. CIEE/spring Monteverde Costa Rica.

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Richards, P. W. 1996. The Tropical Rain Forest: an ecological study. Cambridge University Press, Cambridge. Seidler, T. G. 1992. Some observations on the abundance and distribution of canopy litter invertebrates in a neotropical cloud forest. UCEAP/fall, Monteverde, Costa Rica. Smith, A. P. 1972. Buttressing of tropical trees: a descriptive model and new hypotheses. The American Naturalist 106:32 45. Taize, L and E. Zeiger. 1991. Plant Physiology. Benjamin/Cumming s Publishing Company, New York.

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___________________________________________________________________________________ Table 1. The mean (standard deviation) values for [N], [K], [P], pH, deposition rate and decomposition rate between microhabitat types. Concentrations are measured in lbs/acre, and rates are in g/day. [P] levels are nearing significance (Kruskal Wallis test, p = 0 .0580) with open areas containing much higher concentrations Buttress Non buttress Open area n Parameter Ave. x (s.d.) Ave. x (s.d.) Ave. x (s.d.) [N] 76.667 (64.70) 40 (17.89) 25 (17.61) 6 [K] 173.333 (76.60) 216.667 (48.03) 161.667 (22.29) 6 [P] 58.3 (20.41) 35 (23.45) 108.3 (73.60) 6 pH 6.3 (0.17) 6.13 (0.16) 6.3 (0.21) 6 Dep. Rate 0.599 (.294) 0.605 (.284) 0.415 (.314) 10 Decomp. Rate 0.946 (.556) 0.705 (.310) 0.698 (.355) 10