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Efecto del dimetro de Ficus tuerckheimii, presencia del rbol husped, hbitat y orientacin en la diversidad y abundancia de epifitas
Effect of Ficus tuerckheimii diameter, host tree presence, habitat and orientation on epiphyte diversity and abundance
Ficus tuerckheimii, a species of strangler fig found in the cloud forests of Monteverde, is a keystone species for a multitude of animals as well as epiphytic plants. In the study, epiphyte richness on Ficus tuerckheimii was analyzed in order to determine if epiphyte species richness was related to elevation, circumference,
hollowness, location, percent of area covered by epiphytes and compass point orientation. Thirty Ficus tuerckheimii were studied in pasture and forest areas between 1400-1500 m elevations. A significant relationship was found between epiphyte species richness in forest habitats versus open (Mann Whitney
U=28, P=.0083). Significance was also found between species richness and percent area covered (P=.01). More species richness was found on hollow Ficus tuerckheimii, but was not proven significant. These findings suggest that conservation efforts to preserve older forested land may be most important for
preserving epiphyte species richness as well as organism diversity associated with these trees.
Ficus tuerckheimii, un tipo de higuern estrangulador que se encuentra en los bosques nubosos de Monteverde, es una clave de especies de la cual dependen una multitud de animales as como de las plantas epfitas. La diversidad de epfitas en Ficus tuerckheimii se estudi con el fin de determinar si la riqueza de especies de epfitas estuvo afectada por una variedad de factores que incluye la elevacin, circunferencia, el espacio vaco adentro, ubicacin, porcentaje de rea cubierta por epfitas y el punto de orientacin de la brjula. Se estudi treinta Ficus tuerckheimii en las reas con potrero y bosque entre los 1400-1500m de elevacin. Se encontr relaciones significativas entre riqueza de especies y hbitats con bosque as como el porcentaje del rea cubierta. Se encontr una tendencia positiva entre la riqueza de especies y el espacio vaco adentro del Ficus tuerckheimii, pero no se prob que es significativo. Estos resultados sugieren que el terreno con el bosque ms antiguo puede ser ms importante para preservar la riqueza de especies de ficus as como la diversidad de organismos asociados con los rboles.
Text in English.
Monteverde Biological Station (Costa Rica)
Diversidad de especies
Estacin Biolgica de Monteverde (Costa Rica)
Tropical Ecology Summer 2004
Ecologa Tropical Verano 2004
t Monteverde Institute : Tropical Ecology
1 Effect of Ficus tuerckheimii diameter, host tree presence, habitat and orientation on epiphyte diversity and abundance Christina Tierno Department of Biology, University of Maryland, College Park Abstract Ficus tuerckheimii, a species of strangler fig f ound in the cloud forests of Monteverde, is a keystone species for a multitude of animals as well as epiphytic plants. In the study, epiphyte richness on Ficus tuerckheimii was analyzed in order to determine if epiphyte species richness was related to ele vation, circumference, hollowness, location, percent of area covered by epiphytes and compass point orientation. Thirty Ficus tuerckheimii were studied in pasture and forest areas between 1400 1500 m elevations. A significant relationship was found betwee n epiphyte species richness in forest habitats versus open (Mann Whitney U=28, P=.0083). Significance was also found between species richness and percent area covered (P=.01). More species richness was found on hollow Ficus tuerckheimii , but was not pro ven significant. These findings suggest that conservation efforts to preserve older forested land may be most important for preserving epiphyte species richness as well as organism diversity associated with these trees. Resumen Ficus tuerckheimii , un t ipo de higuerÃ³n estrangulador que se encuentra en los bosques nubosos de Monteverde, es una especial clave de la cual dependen una multitude de animals asÃ como de plantas epÃfitas. La diversidad de epÃfitas en Ficus tuerckheimii se estudiÃ³ con el fin de determinar si la riqueza de especias de epÃfitas estuvo afectada por una variadad de factores que incluye elevacÃon, circunferencia, el espacio vacÃo adentro, ubicacÃon, porcentaje de area cubierta por epÃfitas y el punto de orientaciÃ³n de la brujula. Se estudiÃ³ trenta Ficus tuerckheimii en areas con potrero y bosque entre 1400 1500m de elevaciÃ³n. Se encontrÃ³ relaciones significativas entre riqueza de especias y habitates con bosque asi como el porcentaje de area cubierta. Se encontrÃ³ una tendencia posit iva entre riqueza de especias y el espacio vacio adentro de Ficus tuerckheimii , pero no se probÃ³ que es significativo. Estos resultados sugieren que terreno con bosque mÃ¡s antiguo puede ser mÃ¡s importante para preservar riqueza de especias de ficus asi co mo diversidad de organismos asociados con los Ã¡rboles. Introduction Strangler figs ( Ficus , Moraceae) serve as very important tree species in tropical forests. According to Putz and Holbrook (1986), strangler figs begin as epiphytes in canopy trees; thei r root systems grow toward the ground, increasing nutrient and water availability. After reaching the forest floor, the roots coalesce, forming a self supporting, very irregular trunk. The crevices formed by the roots are home to a multitude of plant and animal species. Fruit production makes stranglers a keystone species to ecosystems in the tropics (Forsyth 1984). The interior of strangler figs is hollow once the host tree dies. It is thought that the cause of death of the host tree is shading of its crown by the fig rather than its tightly fused roots. Ficus tuerckheimii (Moraceae) is a prevalent canopy species of strangler, in the Monteverde Cloud Forest, Costa Rica, with an average height of 20 40 meters (Haber, 2000).
2 Epiphytes are also an eco logically important group of organisms, as they make up one third of lowland flora and account for 60% of individual plants in the Neotropics (Rundel 1996). Epiphyte biomass in Neotropical forests can comprise 35 50% of tree leaf biomass (Tanner 1977). E piphytic diversity and abundance has been shown to enlarge mineral availability to the ecosystem (Nadkarni 1986), and they provide significant contributions to nutrient cycling as well as habitats for small microorganisms (Delacroix 2001). Thus, strangler figs are of further importance to tropical forests by housing this abundant group of plants. The purpose of this study was to determine if epiphytic diversity and coverage on F. tuerckheimii was related to tree circumference and whether the tree was hol low. It was hypothesized that there would be a positive correlation between epiphyte diversity and coverage and tree circumference and significantly more epiphytes on hollow trees. Species richness was also compared between orientation (North, South, Eas t, West) and whether the F. tuerckheimii was found in pasture or forest. These comparisons were used to determine what factors significantly influence epiphytic richness on F. tuerckheimii for the purpose of identifying which aspects are the most important to both epiphyte and fig conservation. Materials and Methods Study Site Epiphyte load on Ficus tuerckheimi was measured at the EstaciÃ³n BiolÃ³gica and surrounding areas within the Monteverde community, between the elevations of 1400 1500 meters. F. tue rckheimi in both pasture and secondary forested areas were sampled. Sample Collection Thirty Ficus tuerckheimi were located for data collection within this narrow elevation gradient to minimize elevational effects on epiphytic diversity and coverage. For each tree, epiphyte species, coverage and diameter at breast height (DBH) of each F. tuerckheimi was measured. Data was determined using a one half square meter grid attached to the tree. Measurements were restricted to four samples taken at breast hei ght on each tree at the four cardinal directions (N,S,E,W). The number of morphospecies and percent coverage of each as well as total percent cover of all epiphytes found within the grid was recorded. Via the grid, direct observation was used to assess t he percent of epiphyte cover for each type of morphospecies as well as total epiphytic cover for each compass point. Digital images were taken of the epiphytes found using a digital Sony Cybershot camera in order to aid in identification. Species were det ermined to genus and family. Hollowness was defined as a completely decomposed host tree, leaving only the strangler fig standing. If the host tree was still present or decomposing, the Ficus tuerckheimii Sample An alysis A simple linear regression was used to ascertain if fig tree circumference was correlated with epiphyte richness, coverage and abundance. Simple linear regressions were also used to determine if elevation influenced species richness and percent co ver. ANOVAs were used to compare cardinal orientation vs. species richness and percent of epiphyte cover. A Mann Whitney U test was used between hollow and solid trees and forest and pasture trees to compare species richness.
3 Results Epiphytic species richness was not significantly related to the distance of F. tuerckheimii trees (simple linear regression). Species richness was higher in hollow F. tuerckheimii trees but the difference was not statistically significant (P=0.08). Species richness was si gnificantly positively related to percent epiphyte cover (simple regression, P=0.01)(Fig. 1). Cardinal orientation was found not be a significantly related to percent epiphyte cover or species richness and elevation over the narrow range sampled was not s ignificantly correlated with either species richness or percent cover (simple linear regression). In comparing a sample size of 11 randomly selected Ficus tuerckheimii in pastures and 11 in forests, the species richness of epiphytes was found to be signifi cantly greater on the 11 F. tuerckheimii in forested areas than pasture areas (Mann Whitney U=28, P=0.0083) (Fig. 2). Discussion Epiphyte species richness was not found to be significantly positively related to F. tuerckheimii circumference as predicted. This may be because as F. tuerckheimii ages and increases in diameter the roots continue to coalesce, leaving less available crevices for epiphyte colonization. More epiphyte species were found on hollow trees than solid trees though it was not quite s tatistically significant. This may indicate that older trees, judged by level of host tree deterioration harbor more species. A significantly greater epiphytic richness was found on Ficus tuerckheimii in forested areas then in pastures. This may be due to an increased exposure to wind and harsh climate conditions in open areas making survival more difficult. Although trees were sampled in different conditions, comparative analysis was done and found that equal distributions of hollow trees and of circu mference ranges were found in both forest and pasture areas. This should, therefore, not affect the rest of the analyses preformed. Species richness was significantly correlated with percent epiphyte cover as expected. The more species present the more area of the tree was being covered. High area coverage increases available habitat for epiphyte dwelling organisms, therefore increasing overall diversity and importance for conservation. Orientation of sample did not affect the percent of area covered by epiphytes or species richness. A relationship was expected because it was thought that there would be more moisture on the North East sides due to the mist rolling over the Tilaran Mountain Range from prevailing N E trade winds. Elevation was not a si gnificant factor in species richness or percent cover, indicating that it was controlled by sampling within a narrow elevation range. In future studies it may be helpful to classify the epiphytes found to genus at minimum to get a more accurate measure of species richness. There are many factors that can affect epiphytic diversity and cover such as level of disturbance, moisture availability and amount of light gaps (Putz, 1986). Future studies should take these factors into account in order to more tigh tly control for these variables and get more accurate results of what influences epiphyte species richness on Ficus tuerckheimii. From the data collected, it can be inferred that hollow F. tuerckheimii found in forested areas have the most epiphyte species . As hollowness may indicate age and result
4 in higher epiphyte species richness, older forest areas, where large F. tuerckheimii can be found with fully decomposed host trees, will harbor the most diversity and abundance. This implies that areas of mature forest are most important for conservation of epiphyte diversity on F. tuerckheimii . Acknowledgements Thank you to Carlos for identifying massive amounts of epiphytes and help all along the way. Ollie and Maria, thanks for your computer genius and the h arsh editing. Carmen, thanks for the moral support. Thanks most of all Margaret for the late night pep talks. Literature cited Delacroix, D. 2001. Community structure of vascular epiphytes in a Costa Rican elfin forest. Forsyth, A. and K. Miyata. 1984. Tropical nature. New York. Haber, W. A., W. Zuchowski, and E. Bello. 2000. An introduction to cloud forest trees Monteverde, Costa Rica. Second Edition. Nadkarni, N.M. 1986. The nutritional effects of epiphytes on host trees with special r eference to alternation of precipitation chemistry. Puts, F.E., and M Holbrook. 1986. Notes on the natural history of hemiepiphytes. Rundel, P. W. and A. C. Gibson. 1996. Adaptive strategies of growth form and physiological ecology in neotropical low land rain forest plants. Tanner, E.V. J. 1977. Four montane rain forests of Jamaica: a quantitative characterization of the floristics, the soils and the foliar mineral levels, and a discussion of the interrelations. Journal of Ecology 65 : 885 918.
5 Figure 1. A significant relationship was found between epiphyte species richness on and average % coverage 30 F. tuerckheimii (Y=1.571 +.058* X) (R^2=.523) (P=0.01) Figure 2. Significantly more species of epiphytes were found on F. tuerckh eimii in forested areas (N=11) than pasture areas (N=11) (Mann Whitney U, U=28, P=0.008). Average % Cover Species Richness 8 7 6 5 4 3 2 1