1,720,972 research outputs found
The contribution of cacao agroforests to the conservation of lower canopy ant and beetle diversity in Indonesia
No full textThe ongoing destruction of tropical rainforests has increased the interest in the potential value of tropical agroforests for the conservation of biodiversity. Traditional, shaded agroforests may support high levels of biodiversity, for some groups even approaching that of undisturbed tropical forests. However, it is unclear to what extent forest fauna is represented in this diversity and how management affects forest fauna in agroforests. We studied lower canopy ant and beetle fauna in cacao agroforests and forests in Central Sulawesi, Indonesia, a region dominated by cacao agroforestry. We compared ant and beetle species richness and composition in forests and cacao agroforests and studied the impact of two aspects of management intensification (the decrease in shade tree diversity and in shade canopy cover) on ant and beetle diversity. The agroforests had three types of shade that represented a decrease in tree diversity (high, intermediate and low diversity). Species richness of ants and beetles in the canopies of the cacao trees was similar to that found in lower canopy forest trees. However, the composition of ant and beetle communities differed greatly between the agroforest and forest sites. Forest beetles suffered profoundly from the conversion to agroforests: only 12.5% of the beetle species recorded in the forest sites were also found in the agroforests and those species made up only 5% of all beetles collected from cacao. In contrast, forest ants were well represented in agroforests, with 75% of all species encountered in the forest sites also occurring on cacao. The reduction of shade tree diversity had no negative effect on ants and beetles on cacao trees. Beetle abundances and non-forest ant species richness even increased with decreasing shade tree diversity. Thinning of the shade canopy was related to a decrease in richness of forest ant species on cacao trees but not of beetles. The contrasting responses of ants and beetles to shade tree management emphasize that conservation plans that focus on one taxonomic group may not work for others. Overall ant and beetle diversity can remain high in shaded agroforests but the conservation of forest ants and beetles in particular depends primarily on the protection of natural forests, which for forest ants can be complemented by the conservation of adjacent shaded cacao agroforests
Shade tree management affects fruit abortion, insect pests and pathogens of cacao
No full textThe mortality of cacao fruits caused by early fruit abortion or insect and pathogen attacks was investigated in differently managedagroforestry systems in Central Sulawesi, Indonesia. Nine agroforestry systems shaded by three different types of tree stands were selected,which represented a decrease in structural heterogeneity: forest remnants, diverse planted trees and one or two species of planted leguminosetrees. After standardized manual cross-pollination, the development of 600 fruits on 54 trees (6 trees per agroforest) was followed during 18weeks of fruit development. In total, 432 of all fruits were lost before maturity, which seriously undermined yields. The proportion ofharvested fruits per tree (overall average: 27 4%) was not affected by canopy type. Although shade cover did not have a significant effect,losses due to fruit abortion were most likely under forest shade, where nitrogen-fixing leguminose shade trees were absent. Fruit losses due topathogenic infections and insect attacks increased with the homogenization of the agroforests, supporting the hypothesis that agriculturalhomogenization increases risks of pest outbreaks. In conclusion, shade management may be improved to increase yields from cacao usinghighly diversified natural shade agroforestry systems
Is productivity of cacao impeded by epiphytes? An experimental approach
No full textThe impact of epiphytes on cacao productivity was investigated in agroforests in Central Sulawesi, Indonesia. Effects of epiphyte removal on fruit-set success and eventual yields were studied on 80 trees in an experiment with a balanced full factorial design. The removal treatment had no significant effect on the eventual harvest of the cacao trees. Pollinator availability had the greatest impact on fruit-set success, whereas yields were mainly determined by site-specific factors that mediate fruit-abortion and occurrence of fungal diseases. The results illustrate that epiphytic flora dominated by non-vascular species may have no effects on cacao tree functioning and removal of non-vascular epiphytes is unnecessary for improving the productivity of cacao. Hence, farmers' labour can be reduced and conservation of the rich biodiversity outside natural forests supported. (c) 2007 Elsevier B.V. All rights reserved
Long-term change of ant community structure in cacao agroforestry landscapes in Indonesia
No full textLand-use change and agricultural intensification can strongly affect biodiversity in agricultural landscapes. Although many studies investigate management impacts, data on the long-term change of species communities in agroecosystems are scarce. We analysed the long-term change in diversity and composition of ant communities in cacao agroforestry systems in Central Sulawesi, Indonesia and attempted to disentangle the driving factors of this change. Ant communities were resampled in 2009 from sites for which previous surveys had been conducted either in 2001 (the rainforest-poor Palolo region) or 2003 (the rainforest-rich Kulawi region) using insecticide fogging. Ant community composition changed significantly over time in Palolo and Kulawi. The change in ant species richness differed between regions. Species richness increased in Kulawi, probably due to the increasing availability of nest sites and microhabitats as trees grow larger and older. In the Palolo region, species richness decreased, suggesting that the high local intensification and landscape-wide changes may have counteracted the effects of tree age. Changes in ant communities over time were significant, but were more difficult to explain than expected, despite clear difference in management changes within and between regions. The findings suggest that the landscape-scale differences between the two study regions play a more important role for species diversity and its composition than changes in local management. This highlights the importance of long-term studies across contrasting landscapes for better understanding the consequences land-use intensification has on tropical biodiversity
Bryophytes on tree trunks in natural forests, selectively logged forests and cacao agroforests in Central Sulawesi, Indonesia
No full textForest disturbance and transformations into agricultural land alter tropical landscapes at drastic rates. Here, we investigate bryophyte assemblages on trunk bases in natural forest, selectively logged forest and cacao agroforests that are shaded by remnants of natural forest in Central Sulawesi. Overall, bryophyte richness per site did not differ between forest types. However, mosses and liverworts reacted differently in that moss richness was lowest in cacao agroforests, whereas liverwort communities were equally rich in all forest types. In terms of cover, mosses remained unaffected while liverwort cover decreased significantly in disturbed forest. Species composition of bryophytes clearly changed in cacao agroforests as compared to natural forests and selectively logged forests. In particular some drought-sensitive species were rare or absent in cacao agroforests and were replaced by drought-tolerant ones, thus underlining the importance of microclimatic changes. Moreover, differences in bryophyte species composition between large and small trees were only pronounced in cacao agroforests, presumably due to concomitant changes in stemflow of precipitation water. In conclusion, the bryophyte assemblages of selectively logged forests and cacao agroforests were as rich as in natural forest, but species turn-over was particularly high towards cacao agroforests probably due to microclimatic changes. Maintenance of shade cover is crucial to the conservation of the drought-sensitive forest species. (c) 2008 Published by Elsevier Ltd
Vertical distribution of epiphytic bryophytes in an Indonesian rainforest
No full textWe studied species richness, composition and vertical distribution of epiphytic bryophytes in submontane rainforest of Central Sulawesi. Bryophytes were sampled on eight canopy trees and on eight trees in the forest understorey. Microclimate was measured at trunk bases and at crown bases. The total recorded number of 146 epiphytic bryophyte species is among the highest ever reported for tropical forests and underlines the importance of the Malesian region as a global biodiversity hotspot. Species composition differed significantly between understorey trees and canopy tree trunks on the one hand, and the forest canopy on the other. Fourty-five percent of the bryophyte species were restricted to canopy tree crowns, 12% to the understorey. Dendroid and fan-like species mainly occurred in the forest understorey whereas tufts were most species rich in the tree crowns. The findings reflect the different microclimatic regimes and substrates found in the understorey and in the forest canopy. The results indicate that assessments of the bryophyte diversity of tropical forests are inadequate when understorey trees and tree crowns are excluded
Microclimate determines community composition but not richness of epiphytic understory bryophytes of rainforest and cacao agroforests in Indonesia
No full textManagement intensification in cultivated, tropical forests drives changes in the microclimate that can threaten native forest. ora and fauna. In this study, we use epiphytic bryophytes, known to be sensitive to microclimatic changes due to their lack of a protective cuticle and the exposed habitat, to investigate the predictive power of microclimate for changes in species richness and composition. Bryophytes were sampled from understory trees in natural forest and cacao (Theobroma cacao L.) trees in two types of cacao agroforests (natural shade trees and planted shade trees) in Central Sulawesi, Indonesia. The microclimate in the agroforests was characterised by low air humidity and high air temperature during the afternoon. Bryophyte species richness did not differ between habitat types but species composition changed markedly from the natural forest to the cacao agroforests. Although no correlation between species richness and microclimate values could be found, a series of matrix-based analyses revealed a significantly positive relationship between similarities in species composition and inmaximum values for temperature and minimum values for humidity, which suggests that microclimatic changes are a good predictor for high turnover of bryophyte community composition from natural forests to cacao agroforests.German Research Foundation [DFG-SFB 552]; European Communit
Advances in pollination ecology from tropical plantation crops
No full textAlthough ecologists traditionally focus on natural ecosystems, there is growing awareness that mixed landscapes of managed and unmanaged systems provide a research environment for understanding basic ecological relationships on a large scale. Here, we show how tropical agroforestry systems can be used to develop ideas about the mechanisms that influence species diversity and subsequent biotic interactions at different spatial scales. Our focus is on tropical plantation crops, mainly coffee and cacao, and their pollinators, which are of basic ecological interest as partners in an important mutualistic interaction. We review how insect-mediated pollination services depend on local agroforest and natural habitats in surrounding landscapes. Further, we evaluate the functional significance of pollinator diversity and the explanatory value of species traits, and we provide an intercontinental comparison of pollinator assemblages. We found that optimal pollination success might be best understood as a consequence of niche complementarities among pollinators in landscapes harboring various species. We further show that small cavity-nesting bees and small generalist beetles were especially affected by isolation from forest and that larger-bodied insects in the same landscapes were not similarly affected. We suggest that mixed tropical landscapes with agroforestry systems have great potential for future research on the interactions between plants and pollinators
The invasive Yellow Crazy Ant and the decline of forest ant diversity in Indonesian cacao agroforests
No full textThroughout the tropics, agroforests are often the only remaining habitat with a considerable tree cover. Agroforestry systems can support high numbers of species and are therefore frequently heralded as the future for tropical biodiversity conservation. However, anthropogenic habitat modification can facilitate species invasions that may suppress native fauna. We compared the ant fauna of lower canopy trees in natural rainforest sites with that of cacao trees in agroforests in Central Sulawesi, Indonesia in order to assess the effects of agroforestry on occurrence of the Yellow Crazy Ant Anoplolepis gracilipes, a common invasive species in the area, and its effects on overall ant richness. The agroforests differed in the type of shade-tree composition, tree density, canopy cover, and distance to the village. On average, 43% of the species in agroforests also occurred in the lower canopy of nearby primary forest and the number of forest ant species that occurred on cacao trees was not related to agroforestry characteristics. However, A. gracilipes was the most common non-forest ant species, and forest ant richness decreased significantly with the presence of this species. Our results indicate that agroforestry may have promoted the occurrence of A. gracilipes, possibly because tree management in agroforests negatively affects ant species that depend on trees for nesting and foraging, whereas A. gracilipes is a generalist when it comes to nesting sites and food preference. Thus, agroforestry management that includes the thinning of tree stands can facilitate ant invasions, thereby threatening the potential of cultivated land for the conservation of tropical ant diversity
Caveats to quantifying ecosystem services: fruit abortion blurs benefits from crop pollination
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