Stefan Graf

PDF der Diplomarbeit im Hochschulschriften-Service der Universität Wien

Diversity and resource use of understorey bats in forest and agroforestry systems at the margin of Lore Lindu National Park (Central Sulawesi, Indonesia)

Tropical landscapes are increasingly dominated by agriculture. However, still little is known about the contribution of land-use systems to preserving tropical biodiversity. Particularly, species that survive in forest remnants often interact closely with these agro-ecosystems. This study quantifies for the first time the importance of agroforestry systems in maintaining species diversity of forest understorey bats in Sulawesi, Indonesia. Therefore, we compared bat diversity of forest and cacao agroforestry systems and tested how changes in bat species assemblages are related to changes of structural habitat complexity. Bats were sampled by mist-netting in the understorey of natural forest, secondary forest and cacao agroforestry systems with a heterogeneous and a homogeneous shade tree layer (N = 4 replicate sites per habitat type) in Kulawi Valley at the western margin of Lore Lindu National Park. A total of 13 species were recorded during 8,592 net-meter-hours. The richness estimators Chao 2 and second-order Jackknife indicated a completeness of our species inventories of 62.2 and 79.8%, respectively. Abundances and species richness were greater in the understorey of agroforestry systems than in forests. Especially agroforestry systems with a diverse layer of shade trees (partly remaining from the formerly logged natural forest) and embedded in the forest margin appeared to harbor a high fraction of the local bat assemblage. Species composition did not differ between habitat types; rather bat assemblages appeared to be nested. However, results have to be interpreted cautiously due to the very small sample size achieved for our forest sites. Mean canopy closure and density of tall trees (dbh ≥ 50 cm) differed significantly between habitats. The abundance of two bat species (Cynopterus brachyotis and Rousettus amplexicaudatus) was negatively affected by increasing canopy closure; the abundance of one bat species (Rousettus celebensis) was negatively correlated with the number of tall trees. Other species showed at least a similar trend of decreasing abundances with increasing canopy closure and density of large trees. Our results suggest that cacao agroforestry systems have the potential to act as important feeding habitats for bats in the buffer zone of protected forest remnants in Indonesia.