Members Only: Biotic interactions in the tropics - challenges for restoration and conservation
Wednesday, September 12, 2018
Posted by: Rebecca Shoer
Biotic interactions in the tropics_ challenges for restoration and conservation in the Anthropocene from Society for Ecol. Restoration on Vimeo.
When ecosystems are lost or transformed, not only is biodiversity simplified or displaced, but key interactions that modulate ecosystem structure and function are also affected. Therefore, restoration and conservation must have a complete view of the ecosystems to ensure their recovery.
This webinar explores how biotic interactions influence the restoration of natural tropical ecosystems. We examine how feeding interactions, such as predation and frugivory, affect the carbon cycle in the soil-atmosphere and in the trees. In addition, we will discuss changes in animal composition that may induce changes in the spatial organization of tree cohorts and its implication for restoration as a strategy for reviving and sustaining forests.
Finally, we will explore how changes in animal composition (pollinators and disperser) can be partially reversible if we develop functional ecosystem restoration strategies.
Mammal diversity influences the carbon cycle through trophic interactions in the Amazon.
Mar Sobral Department of Biology, Stanford University, Stanford, CA, 94305, USA
Department of Zoology, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain
Biodiversity affects many ecosystem functions and services, including carbon cycling and retention. While it is known that the efficiency of carbon capture and biomass production by ecological communities increases with species diversity, the role of vertebrate animals in the carbon cycle remains undocumented. Here, we use an extensive dataset collected in a high-diversity Amazonian system to parse out the relationship between animal and plant species richness, feeding interactions, tree biomass and carbon concentrations in soil. Mammal and tree species richness is positively related to tree biomass and carbon concentration in soil—and the relationship is mediated by organic remains produced by vertebrate feeding events. Our research advances knowledge of the links between biodiversity and carbon cycling and storage, supporting the view that whole community complexity—including vertebrate richness and trophic interactions—drives ecosystem function in tropical systems. Securing animal and plant diversity while protecting landscape integrity will contribute to soil nutrient content and carbon retention in the biosphere.
Defaunation increases the spatial clustering of lowland Western Amazonian tree communities.
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA
Declines of large vertebrates in tropical forests may reduce dispersal of tree species that rely on them, and the resulting undispersed seedlings might suffer increased distance- and density-dependent mortality. Consequently, extirpation of large vertebrates may alter the composition and spatial structure of plant communities and impair ecosystem functions like carbon storage. We analysed spatial patterns of tree recruitment within six forest plots along a defaunation gradient in western Amazonia. Defaunation increased the spatial aggregation of saplings of tree species reliant on hunted dispersers. The increase in sapling clustering persisted into older recruit cohorts, suggesting that hunting may initiate long-term spatial reorganisation of Amazonian tree communities. The lack of increased density-dependent thinning indicates that reduced dispersal did not increase mortality of large-vertebrate dispersed tree species that contribute disproportionately to forest biomass. We, therefore, caution against the fait accompli acceptance of the prediction by recent modelling studies that overhunting will precipitate a collapse in carbon sequestration by tropical forests.
Ecosystem restoration strengthens pollination network resilience and function
Christopher N. Kaiser-Bunbury
Senior Lecturer in Ecology & Conservation, Centre for Ecology and Conservation, University of Exeter, UK
Restoration of native plant communities is one strategy to mitigate the negative impacts of biodiversity loss, but there is little knowledge on whether restoration has a positive effect on ecosystem functions. In this study we monitored plant-pollinator interactions and pollination success over a full tropical field season (8 months) and across eight isolated mountaintop communities in the Seychelles, four of which had all exotic shrubs removed, the other four remained unchanged. We showed that restoration increased the number of pollinator species and native plan productivity. Changes in pollinator behaviour resulted in increased pollination, suggesting that the degradation of ecosystems through the introduction of exotic species is at least partially reversible. We proposed that the observed improvements to pollination may be in part due to the removal of exotic plants making native plants more accessible to pollinators.
Successional status, seed dispersal mode and overstorey species influence tree regeneration in tropical rain-forest fragments in the Western Ghats, India
Anand M. Osuri
Department of Ecology, Evolution and Environmental Biology, Columbia University.
Natural regeneration of tree communities in tropical forests is governed by several factors including abiotic conditions such as light and soil nutrients and biotic processes such as seed dispersal by animals. Anthropogenic disturbances such as forest fragmentation drive marked changes in both abiotic environments and biotic processes, resulting in altered and often diminished regeneration of forest trees in tropical human-dominated landscapes. Drawing on our scientific research and restoration efforts in India’s Western Ghats mountains, I will explore ideas on: (1) animal seed dispersal and its significance alongside other factors such as shade and soil for natural regeneration and recovery of degraded tropical forests; and (2) the importance and potential limitations of restoration as a strategy for reviving and sustaining forests with old-growth tree species in human-dominated tropical landscapes.