Abstract booklet - gtö – Society for Tropical Ecology

48 PARALLEL SESSION H IV: CLIMATE CHANGE AND SEASONALITYPARALLEL SESSION H IV: CLIMATE CHANGE AND SEASONALITY49MODELLING THE DYNAMICS OF RAINFORESTS. HOW STRONG ISTHE IMPACT OF DROUGHT ON TROPICAL RAINFORESTS IN MADA-GASCAR?INFLUENCE OF CLIMATIC SEASONALITY ON THE DIVERSITY ANDASSEMBLAGE COMPOSITION OF HUMMINGBIRDS AND THEIRFOOD PLANTS: WHAT CAN WE DEDUCE FOR CLIMATE CHANGE?Rico Fischer 1 , Hans-Jürgen Dobner 2 , Andreas Huth 1Stefan Abrahamczyk 1 , Michael Kessler 21 Helmholtz-Centre UFZ, Leipzig, DE, rico.fischer@ufz.de, 2 2HTWK Leipzig - Universityof Applied Sciences, Leipzig, DE1 University of Zurich, Zurich, CH, abraha@systbot.uzh.ch, 2 University of Zurich,Zurich, CHTUESDAY 10:15 Hall H IVThe rainforests in Madagascar with their high degree of endemism belong tothe hot spots of biodiversity. Since up to 90% of forests are destroyed, many scientistsbelieve that they should be considered among the highest conservationpriorities on Earth.The long-term responses of forests on droughts cannot be easily measured.Therefore and for extrapolations of short-term field measurements we needvegetation models. In this study we use the process-based, individual-orientedsimulation model FORMIX3. The main processes of this model are tree growth,mortality, regeneration and competition. Tree growth is calculated on a carbonbalance. The parameters of the model have been estimated based on field dataof a rainforest in the south of Madagascar. This data has also been used to developstem diameter increment functions by statistical methods.The objective of this study is to understand how drought modifies biomass,species composition, productivity and carbon flux of a rainforest as a functionof annual rainfall. The impact of drought on plants is modeled by calculatingstress factors. Depending on the scenarios we observed a reduction of 30% inbiomass and 40% in production.Hummingbirds mainly feed on nectar and are thus strongly linked to their foodplants. We conducted a survey of hummingbirds and their food plans along alatitudinal gradient in six Bolivian lowland forests. The latitudinal gradient alsorepresents a gradient in temperature and precipitation seasonality. At each locality,species numbers of hummingbirds and their food plants as well as hummingbirdabundance and numbers of flowers were registered once in both therainy and dry seasons. We found that climatic seasonality had a strong impacton the diversity of food plant species, which in turn determines the number offlowers and hence nectar availability. Species number and abundance of hummingbirdswas related to the number of flowers but not to the diversity of foodplants. Focussing on changes in species richness and assemblage compositionbetween seasons, climatic seasonality was the most important factor. Therefore,we predict that climate change will mainly directly affect the hummingbirdfood plants. These in turn will have an influence on the diversity and assemblagecomposition of hummingbirds. However, because the abundance of singlefood plants has far-reaching impacts on the hummingbird assemblages, specificresponses of hummingbird assemblages to climate change are impossibleto predict.TUESDAY 10:30 Hall H IVgtöSociety for Tropical Ecology | Gesellschaft für Tropenökologie e.V. Status and future of tropical biodiversity | Frankfurt, 21 - 24 February 2011gtö