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Forest regeneration under Ficus tuerckheimii and Sideroxylon portoricense in former pasturelands. Michael Perkins Department of Biological and Environmental Sciences, Morehead State University, Morehead, Kentucky, 40351, USA Abstract Forest regenerati on in abandoned pastures is often slower than in areas of natural disturbance. Lack of seed dispersers is often the major limiting factor. Shade trees left in pastures are potential perch sites and food sources for birds that act as seed dispersers. This study compared diversity and stem density of colonizing tree species under the crowns of Ficus tuerckheimii and Sideroxylon portoricense and compared change in diversity from a previous study measuring the same parameters at the same site. Ficus tuerckhe imii had a significantly greater diversity of seedlings than Sideroxylon portoricense For Ficus and Sideroxylon significant negative correlation was found between stem density and distance from the trunk of both species. Both species of trees are effect ive as nuclear species for seed dispersal and aid in accelerating forest regeneration. Resumen La regeneracin de bosques en potreros abanonados es a menudo ms lenta que en areas con perturbaciones naturales. La falta de dispersores de semillas es el factor restrictivo ms importante. Los rboles para sombra en los potreros son lugares de percha potencial y de fuentes de comida para aves que son dispersores de semillas. Este estudio compar la diversidad y densidad de tallos de especies de rboles colonizadoras debajo de las copas de Ficus tuerckheimii y Sideroxylon portoricense Se compar el cambio de la diversidad con un estudio anterior que midi las mismas caractersticas en el mismo sitio. Ficus tuerckheimii present una diversidad consider ablemente mayor de plntulas que Sideroxylon portoricense Las dos especies, Ficus y Sideroxylon mostraron una correlacin negativa significativa entre la densidad de tallos de plntulas y la distancia al tronco de ambos rboles. Ambas especies de rb oles son efectivas como especies clave para la dispersin de semillas y ayudan a acelerar la regeneracin del bosque. Introduction Abandoned pastures are poor sites for forest regeneration and are often slower in recovery as compared to disturbance types such as hurricane and treefall gaps (Cubina and Aide 2001). This can result from factors such as predation of seeds and seedlings, destruction of the seedbank due to trampling, shortage of mycorrhizae and competition with grasses (Nepstad et al. 1990, Cu bina and Aide 2001). Attraction of seed dispersers is crucial to replenishing the seed bank and subsequently, regenerating abandoned pastures. Seed recruitment is an important component of the regeneration of pastures and is dependent on dispersal by ver tebrates, especially birds, or by wind. Many species of birds are less likely to disperse seeds into agricultural sites due to their avoidance of open areas, which may increase their risk of predation (Howe and Smallwood 1982, Groom 2000). This limits th e types of plants that will be recruited into regenerating areas
(Groom 2000, Tabarelli and Peres 2002). The presence of shade trees in abandoned pastures can foster regeneration of forests by attracting birds and arboreal mammals, which have the potential to function as seed dispersers (Holl 1999). Habitat loss, fragmentation, and selective hunting have led to the loss of large gaped bird species and large mammals that are capable of dispersing large seeds in Malaysia (Corlett 1998). These pressures are present in Costa Rica as well. Studying tree species composition in regenerating pastures over time can indicate if management practices are effectively aiding in the replenishment of the tree species found in the areas pre disturbance. The density of recolonizing species around shade trees has been shown to be greater than the densities observed in edges or open areas (Groom 2000). Schuster (2000) evaluated regeneration effectiveness of two shade tree species, Ficus tuerckheimii (Moraceae) and Siderox ylon portoricense (Sapotaceae), in an abandoned pasture in Monteverde, Costa Rica. He used the diversity of seedlings under and near the shade significant difference i n regenerating plant diversity between the areas under the canopies of Sideroxylon portoricense and Ficus tuerckheimii The goal of this study was to repeat seedling s as a function of shade tree type and distance from the trunk of the shade tree. It is predicted that this study will show no significant differences in the trends observed by Schuster. Methods and Materials Study Site The study site was located in pre montane moist lifezone (Holdridge) with an average rainfall of 2519 mm/yr (Clark et al. 2000). The study was conducted on a (ca. 5 ha.) farm located near the main road in Monteverde, Costa Rica, across from the Monteverde lly belonged to the late Miguel and Molly Figuerola, who willed the property to the Monteverde Conservation League (MCL). From 1976 1995, the farm was used for dairy production during which, the understory vegetation was cleared and planted with Cynodon n lemfuensis (Poaceae). Cows were removed from the land in 1995, at which point regeneration began. The methods followed Schuster (2000) with the exception of the use of five individuals of each shade around shade trees that were at least 10 m apart so as to avoid crown overlap and seed rain overlap, but two of the S. portoricense (#23 and #41) (the numbering system was established by William Haber after the MCL took over the property) used by Schuster were found to be 7 m apart, so # 41 was excluded from this study. One less F. tuerckheimii was sampled to maintain an even representation of each species. A shade tree from the previous study was misidentified as S. portoricense (#9) and is actually Pout eria exfoliata (Sapotaceae), but was included with the S. portoricense Sampling took place from July 28, 2005 through August 2, 2005. Three transects measuring 10m x 1m, at compass points 0, 120 and 240, were established, beginning 0.5 m from the bas e of each shade tree trunk. The transects were divided into ten 1 m x 1 m plots. Woody plants taller than 50 cm were identified and counted. Percent
herbaceous cover was visually estimated and recorded for plots containing herbaceous vegetation. Plant species were identified to species using help from Dr. Carlos Guindon and Haber et al. (2000). One plant was identified to genus ( Cestrum spp. ) and three were not identified (sp #5, sp 1a, sp 2a). The Shannon Weiner diversity index was used to determine diversity under the two selected species of shade tree. A modified t test was used to determine if a significant difference exists between the diversity indices for the two species. Combined diversity of all plots located a given distance away from the shade tree species were calculated using the Shannon Weiner diversity index. Each distance was compared between the two species using a modified t test to determine if a significant difference between the ten sets of diversity indices existed. A paired t test was used to determine if there was significant difference in stem densities between the two study species as a function of distance. A Spearman rank correlation was used to determine with each Ficus and Sideroxylon if a relationship existed between the distance from shade tree and the diversity and stem density of the plants colonizing underneath. Spearman rank correlations and simple regressions were performed using Statview v.5.0.1 Results Ficus had significantly greater diversity of woody plants Sideroxylon (modified t test, p < 0.001) (Table 2). Diversity as a function of distance from the shade tree trunk showed no significant difference between Ficus and Sideroxylon (paired t test, p = 0.1191). Stem density a s a function of distance from the trunk of Ficus and Sideroxylon also showed no significant difference (paired t test, t = 2.040, p = 0.07). No significant correlation was found between diversity and distance from the trunk of Ficus (R s = 0.382, p = 0.25 2) or Sideroxylon (R s = 0.309, p = 0.354). A significant negative correlation was found between stem density and distance from the Ficus (R s = .770, p = 0.021) and Sideroxylon (R s = .770, p = 0.021) (Figures 1 and 2). Ficus had significantly greater d iversity indices than Sideroxylon at the following distances: 3 m (p < 0.01), 4 m (p < 0.001) and 8 m (p < 0.05) (Table 2). Ficus had a significantly greater diversity test, p < 0.001). Sideroxylon had a significantly t test, p < 0.001). A total of 45 species were found in the 868 stems sampled, under the eight shade trees combined. Ficus had 37 total species and Sideroxylon had 30 total species. Nine of the ten most abundant species were bird dispersed, while only one species in the study was wind dispersed (Table 1). Schuster (2000) sampled 10 trees and found 858 woody individuals in 50 different species with 36 bird and two wind dispersed species. Ficus had 42 species under its crown, while Sideroxylon had 31 species. The data was standardized by dividing the number of shade trees sampled by the number of stems found under their crowns The number of stems per shade tree was 86.8 for both species combined, 98.5 for Ficus and 118.5 for Sideroxylon Schuster found 85.8 stems per shade tree, combined, 108.6 for Ficus and 63 for Sideroxylon (Figure 3). Schuster found 24 species that wer e not found in the current study, with Solanum umbellatum (13) being the only species with 10 or more individuals. The current study found 14 species that were not found by Schuster, with Eugenia acapulcensis (12),
Bunchosia macrophylla (10) and Koanophyl lon pittieri (10) being the only species having 10 or more individuals. Ocotea whiteii represented 44% of all stems under Sideroxylon with 210 individuals. Hampea appendiculata represented 37% of all stems under Ficus with 148 individuals. Discussion The higher species diversity under the Ficus could be attributed to a higher abundance and greater richness of birds providing heavy and diverse seed rain (Wheelright et al. 1984). More birds are likely to visit Ficus for its fruits, which contain small seed s and occur irregularly year round. Birds are also likely to visit Ficus for the fruits of its host (if alive), and its large spreading crown (C. Guindon, pers. comm.). Ocotea whiteii dominated the number of stems (44%) at Sideroxylon plots, which drove down species evenness and thus diversity as compared to Ficus The strong trend of declining stem density as a function of distance from the shade tree base is attributable to physical features provided by the tree. Micro climatic conditions near the base of the trees provide a stable moisture source as well as a relatively stable temperature, which would favor seed germination (Uhl et al. 1982). Dispersers may spend more time near the interior of the tree as it may provide more protection from predators. Density would be lower as you move away from the trunk and the amount of shade is reduced, thus allowing for increased competition for seedlings from herbaceous species, such as Cynodon nlemfuensis which was prevalent throughout remaining pasture areas (Appendix 1). Significantly higher diversity at 3m, 4m, and 8m away from the Ficus as compared to Sideroxylon is not a trend that is supported by other literature. The difference in crown morphologies, between Ficus and Sideroxylon could contribute to th is. Comparing Schuster (2000) to the current study, an 11% decrease in species richness under Ficus was outpaced by the 27% loss in number of stems. These data indicate causation of overall increase in diversity for Ficus between the studies. Under th e Ficus competition for light increases under the developing canopy leading to domination of some species and individuals and suppression of others (Weiner 1990, Vandemeer et al. 2000). Sideroxylon had a 3% loss in richness coupled with a 50% increase i n stem density. Under Sideroxylon O whittei represented approximately 16% of stems in the first study and 44% in the current study, which reduced species evenness and thus diversity. The high ratio of bird dispersed species to wind dispersed species is common in a more mature forest stand (Tabarelli and Peres 2002). These data combined with data occurred at high levels soon after abandonment and has remained high. Acknowledgements I would like express my deep gratitude to Carlos Guindon for guiding me towards this project, teaching me the vast depths of plant identification in the tropics and for shining the light of reason and inspiration when times were dark. Nathaniel Talbot and Maria Jost were instrumental in keeping the smile on my face and making a better life for all those around them. Thank you all.
Literature Cited Corlett, R. T. 1998. Frugivory and seed dispersal by vertebrates in the Oriental(Indo malayan) Region. Biological Review 73: 413 448 Cubina, A., and T. M. Aide. 2001. The effect of distance from forest edge on seed rain and soil seed bank in a tropical pasture. Biotropica 33 (2): 260 267. Groom, M. 2000. Patterns in the regeneration of lauraceous trees in abandoned pastures. In N. Nadkarni and N. Wheelwright (Eds.). Monteverde: ecology and conservation of a tropical cloud forest, pp. 442 444. Oxford University Press, New York Haber, W. A., W. Zuchowski and E. Bello. 2000. An introduct ion to cloud forest trees: Monteverde, Costa Rica, 2 nd ed. Mountain Gem Publications, Monteverde de Puntarenas, Costa Rica Holl, K. 1999. Factors limiting tropical rain forest regeneration in abandoned pasture:seed rain, seed germination, microclimate and soil. Biotropica 30 (2): 229 239. Howe, H. F., and J. Smallwood. 1982. Ecology of seed dispersal. Annu. Rev. Ecol. Syst. 13: 201 228 Clark, K., R. O. Burtn, P.R. Butler. The physical environment. In N. Nadkarni and N. Wheelwright (Eds.). Mont everde: ecology and conservation of a tropical cloud forest, pp. 15 38. Oxford University Press, New York. Nepstad, D., C. Uhl, and E. A. Serrao. 1990. Surmounting barriers to forest regeneration in abandoned, highly degraded pastures: a case study from Paragominas, Para, Brazil. pp. 215 229 In A. B. Anderson (Ed.) Alternatives to deforestation: steps toward sustainable use of the Amazon rainforest. Columbia University Press, New York. Schuster, B. 2000. Regeneration of an abandoned pasture: diversi ty under nuclear trees. CIEE. Monteverde Summer 2000. pp. 13 26. Tabarelli, M. and C.A. Peres. 2002. Abiotic and vertebrate seed dispersal in the Brazilian Atlantic forest: implications for forest regeneration. Biological Conservation 106: 165 176. Uhl, C., H. Clark and K. Clark. 1982. Successional patterns associated with slash and burn agriculture in the upper Rio Negro region of the Amazon Basin. Biotropica 4: 249 254. Vandermeer, J. H., D. H. Boucher, I. G. de la Cerda, and I. Perfecto. 2001. Gro wth and development of the thinning canopy in a post hurricane tropical rain forest in Nicaragua. Forest Ecology and Management 148: 221 242. Weiner, J. 1990. Asymmetric competition in plant populations. Trends in Ecological Evolution 5: 360 364 Wheelr ight, N., W. A. Haber, K. G. Murray, and C. Guindon. 1984. Tropical fruit eating birds and their food plants: a survey Costa Rican lower montane forest. Biotropica 16: 173 192.
Figure 1. Relationship between stem density of woody plants under fou r Ficus tuerckheimii in an abandoned pasture as a function of distance from the tree base (Spearman Rank correlation, R s = .770, p = 0.021). Figure 2. Relationship of stem density of woody plants under Sideroxylon portoricense in an abandoned pas ture as a function of distance from the tree base (Spearman Rank correlation, R s = .770, p = 0.021).
Figure 3. Comparison of stems per tree under Ficus and Sideroxylon from Schuster (2000) and the current study. Table 1. Abundance of plants regenerating under four Ficus tuerckheimii and four Sideroxylon portoricense in an abandoned pasture. The right column shows seed dispersal types (AM = arboreal mammal, BD = bird, BT = bat, BL = ballistic, GR = gravity, TM = terrestri al mammal, WD = wind). Species Total Abundance Ficus tuerckheimii Sideroxylon portoricense Seed Dispersal Ocotea whiteii 212 2 210 BD Hampea appendiculata 173 148 25 BD Ocotea monteverdensis 105 35 70 BD Viburnum costaricanum 70 22 48 BD Styrax argen tatus 48 31 17 BD Cestrum megalophyllum 41 33 8 BD Cinnamomum neurophyllum 34 20 14 BD Nectandra membranaceae 19 8 11 BD Myrsine coriaceae 17 2 15 BD Daphnopsis americana 12 6 6 TM Eugenia acapulcensis 12 6 6 BD, BT Cestrum #2 12 6 6 BD Koanophyllo n pittieri 10 9 1 WD Citharexylum costaricensis 9 9 0 BD Solanum aphyodendron 9 5 4 BT Coffea arabica 8 1 7 BD Sp #5 6 0 6 ?
Pouteria exfoliata 6 2 4 AM Tapirira mexicana 5 4 1 BD Cinnamomum cinnamomifolium 5 4 1 BD Meliosma vernicosa 4 4 0 AM, BD Oreopanax xalapensis 4 4 0 BD Meliosma idiopoda 4 4 0 BD Sapium glandulosum 3 3 0 BD Cupania glabra 3 2 1 BD Erythrina lanceolata 3 2 1 TM Piper hispidum 2 2 0 BT Piper auritum 2 2 0 BT Bunchosia macrophylla 2 0 2 BD Conostegia xalapensis 2 0 2 BD Ocotea tenera 2 2 0 BD Ardisia palmana 2 2 0 BD Erythroxylum macrophyllum 2 2 0 BD Sideroxylon portoricense 2 0 2 BD Palicourea padifolia 1 1 0 BD Quercus insignis 1 1 0 AM, TM Styphnolobium monteviridis 1 1 0 AM Pouteria reticulata 1 0 0 BD Ocot ea floribunda 1 0 1 BD Stauranthus perforatus 1 1 0 BD Cecropia obtusifolia 1 0 1 BD, BT Croton mexicanus 1 0 1 BL Sp 1a 1 0 1 ? Sp 2a 1 0 1 ? Table 2. Overall comparison of diversity under the crown of Ficus and Sideroxylon and comparison of each distance as a function of diversity between Ficus and Sideroxylon Values t v p Distance Ficus Sideroxylon 1 m 1.818 85.689 > 0.05 1.0655 0.9248 2 m 1.379 94.559 > 0.05 0.7959 0.6387 3 m 2.704 115.947 < 0.01 0.8826 0.6270 4 m 4.454 115.889 < 0 .001 1.0569 0.6660 5 m 1.119 79.850 > 0.05 0.9808 0.8517 6 m 1.261 64.815 > 0.05 0.8572 0.9562 7 m 1.970 61.549 > 0.05 0.8020 0.9689 8 m 2.094 83.295 < 0.05 0.8980 0.6843 9 m 1.553 58.321 > 0.05 0.9261 0.7887 10 m 1.358 36.334 > 0.05 0.7492 0.9042 Overall 4.1767 837.032 < 0.001 1.0880 0.9100
Appendix 1. Field notes on transect and plot conditions for four Ficus and four Sideroxylon. Ficus Trans. () Plot(s) Notes #64 120 6 Trunk of tree (#63) through 5% of plot 240 10 Ends at barbed wire fence; 3m from road #77 0 4 10 Entering grassy area; 70% cover with Cynodon nlemfuensis (CN) 120 5 10 Drainage present 240 5 10 Crown of tree (#77) present 7 70% CN 8 9 10 #35 0 8 40% herb. cover; 20% trail cover; @ forest edge 9 40% herb. cover 10 120 7 90% herb. cover; forest edge 9 100% herb. cover 10 #57 0 5 6 7 10 >95% CN 120 1 10 Completely through a tree crown 2 4 Drainage present Siderox. Trans. ( ) Plot(s) Notes #67 0 7 Armadillo burrow 40% 8 Stump 50% 9 50% CN 10 90% CN #23 0 2 30% herb. 3 70% herb. ; 20% trail 4 70% herb. 5 6 60% tree trunk (#61) 7 9 40% herb. 10 30% herb. 120 1 4 Contain tree crown 2 4 100% herb 5 6 7 8 240 1 2 3 5 6 8 9 10 >95% #17 0 3 10 Field edge 5 60% herb. 6 7 8 10 240 9 20% tree trunk (#15) #9 120 6 100% tree trunk (#12) 7
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La regeneracin del bosque debajo de Ficus tuerckheimii y Sideroxylon portoricense en los potreros antiguos
Forest regeneration under Ficus tuerckheimii and Sideroxylon portoricense in former pasturelands.
Forest regeneration in abandoned pastures is often slower than in areas of natural disturbance. Lack of seed dispersers is often the major limiting factor. Shade trees left in pastures are potential perch sites and food sources for birds that act as seed dispersers. This study compared diversity and stem density of colonizing tree species under the crowns of Ficus tuerckheimii and Sideroxylon portoricense and compared change in diversity from a previous study measuring the same parameters at the same site. Ficus tuerckheimii had a significantly greater diversity of seedlings than Sideroxylon portoricense. For Ficus and Sideroxylon,
significant negative correlation was found between stem-density and distance from the trunk of both species. Both species of trees are effective as nuclear species for seed dispersal and aid in accelerating forest regeneration.
La regeneracin de bosques en potreros abandonados es a menudo ms lenta que en reas con perturbaciones naturales. La falta de dispersores de semillas es el factor restrictivo ms importante. Los rboles para sombra en los potreros son lugares de percha potencial y de fuentes de comida para aves que son dispersores de semillas. Este estudio compar la diversidad y densidad de tallos de especies de rboles colonizadoras debajo de las copas de Ficus tuerckheimii y Sideroxylon portoricense. Se compar el cambio de la diversidad con un estudio anterior que midi las mismas caractersticas en el mismo sitio. Ficus tuerckheimii present una diversidad considerablemente mayor de plntulas que Sideroxylon portoricense. Las dos especies, Ficus y Sideroxylon, mostraron una correlacin negativa significativa entre la densidad de tallos de plntulas y la distancia al tronco de ambos rboles. Ambas especies de rboles son efectivas como especies clave para la dispersin de semillas y ayudan a acelerar la regeneracin del bosque.
Text in English.
Costa Rica--Puntarenas--Monteverde Zone
Regeneracin del bosque
Diversidad de especies
Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology Summer 2005
Fig tree (Ficus tuerckheimii)
Ecologia Tropical Verano 2005
Higuern (Ficus tuerckheimii)
t Monteverde Institute : Tropical Ecology