Abstract booklet - gtö – Society for Tropical Ecology

36 PARALLEL SESSION HALL H IV: AFRICAN SAVANNAS BIODIVERSITYPARALLEL SESSION HALL H IV: AFRICAN SAVANNAS BIODIVERSITY 37ABRUPT SHIFTS IN SAVANNA TREE COVERALONG A PRECIPITATION GRADIENTTHE INTERPLAY OF CLIMATE CHANGE AND HUMAN PRESSURE INPREDICTIVE VEGETATION MODELLING, WEST AFRICAMONDAY 15:30 Hall H IVCharly Favier 1 , Laurent Bremond 2 , Julie Aleman 2 , Marc A. Dubois 3 , Jean-Michel Yangakola 4 , Charly Favier 11ISEM - Univ. Montpellier 2, Montpellier, FR, charly.favier@um2.fr, 2 CBAE - Univ.Montpellier 2, Montpellier, France, 3 SPEC - CEA, Saclay, France, 4 Université deBangui, Bangui, Central African RepublicHow savanna tree covers are determined by natural and man-induced forcingsremains under debate. Small-scale studies have led to conflicting models andlarge-scale studies are ambiguous on the link between tree covers and climate.Along a climatic North-South transect in Central Africa, this study aims to answerthree debated questions: is there identifiable mean savanna structure undergiven climate? Does tree cover always increase with water availability or is therea depression in tree cover in the most humid sites? Is there a continuous trendor a stepwise trend? An original analysis of coarse scale satellite date allowed usto show that the vegetation pattern along the transect is made of a successionof stable states, each of them consisting of patches asynchronously exploring awide range of configurations around the average one. The transitions betweenthem are discontinuous transitions, resulting in regions of mosaics of alternativestable states, in contrast with continuous evolution of climate and species pools.The observed large-scale predictability of savanna structures is significant forsavanna modeling, resilience studies and paleoenvironmental studies.Jonathan Heubes 1 , Rüdiger Wittig 1 , Georg Zizka 1 , Karen Hahn 11BiK-F, Frankfurt, DE, jonathan.heubes@senckenberg.deClimate and land use change are the most influential factors for futurebiodiversity. Especially in African savannas, land use change is expected tohave a high impact. Thus, our objectives are (1) to quantify the importance ofland use and climate on plant species distributions across Burkina Faso, WestAfrica and (2) to project future species richness (2050) considering climateand land use changes. To evaluate the importance of land use we ran stepwisegeneralized additive models for each plant species with climatic parameters,only. In a second step, we regressed the residuals of the climate-drivenmodels against the land use variables to extract relevant land use parameters.Finally, we derived future (2050) richness patterns, considering both climateand land use variables. We used the climate model MIROC-medres whileland use simulations were generated by LandSHIFT. Our results partly showan improvement of the explanatory and predictive power of the models inconsideration of land use. Strongly modified plant species richness patternsemerge by 2050, accounting for land use impact. We conclude to consider landuse as an important factor when projecting future species richness patterns forAfrican savanna ecosystems.MONDAY 15:45 Hall H IVgtöSociety for Tropical Ecology | Gesellschaft für Tropenökologie e.V. Status and future of tropical biodiversity | Frankfurt, 21 - 24 February 2011gtö