Format: ORAL

Fabien Spicher1, Flavien Collart2, Thing Shen3,4,5, Marianne Laslier1, Eva Gril1, Alain Vanderpoorten3 Jonathan Lenoir1

1 UMR CNRS 7058 “Ecologie et Dynamique des Systèmes Anthropisés” (EDYSAN), Université de Picardie Jules Verne, Amiens, France 2 Department of Ecology and Evolution (DEE), University of Lausanne, Lausanne, Switzerland 3 Institute of Botany, University of Liège, Liège, Belgium 4 Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, China 5 Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China

At the interface between atmosphere and vegetation, epiphytes are exposed to dramatic variations of light exposure and microclimatic conditions along a tree, from the buffered conditions at the base to the amplified conditions in the outer canopy. They appear therefore as an ideal model to assess the impact of the spatial variation in microclimatic conditions at fine scales and its change under ongoing climate warming. A canopy crane giving access to 1.1 ha of tropical rainforest in Yunnan (China) was used to record hourly light, temperature and relative humidity from 54 sensors during 3 years and 408 plots of epiphytic bryophyte communities. To quantify how microclimates are buffered or amplified relative to macroclimates, we implemented, at each sensor, linear regressions between the hourly variation in microclimate and macroclimate. The slope of this regression represents an integrative parameter describing the buffering (slope 1) or amplification (slope 1) capacity of the canopy. We then employed a series of spatially-explicit predictors of canopy structure derived from a terrestrial LiDAR scan to predict the slope of the macro-microclimate relationship. This resulted in a spatially-explicit model of microclimatic variation in 3D, allowing for predicting the microclimatic conditions that prevail at any point in the canopy under present and future macroclimatic conditions. Microclimatic variation accounted for 33% and 18% of the variation in vertical turnover in mosses and liverworts, respectively, highlighting the crucial role of microclimates in determining the composition of epiphytic communities. Ensemble of small models were finally implemented to predict the distribution of the dominant species under present climatic conditions and evaluate the shift of their distribution under ongoing climate change.