OOS 31-8 - The variation of tree beta diversity across a global network of forest plots

Wednesday, August 8, 2012: 4:00 PM
B110, Oregon Convention Center
Miquel De Cáceres1, Pierre Legendre2, Renato Valencia3, Min Cao4, Li-Wan Chang5, George B. Chuyong6, Richard Condit7, Zhanqing Hao8, Chang-Fu Hsieh9, Stephen P. Hubbell10, David Kenfack11, Keping Ma12, Xiangcheng Mi12, Nur Supardi Md. Noor13, Abdul Rahman Kassim14, Sheng-Hsin Su15, I-Fang Sun16, Duncan Thomas17, Wanhui Ye18 and Fangliang He19, (1)Département de Sciences Biologiques, Université de Montréal, Montréal, QC, Canada, (2)Université de Montréal, Montreal, QC, Canada, (3)Laboratorio de Ecología de Plantas, Herbario QCA, Pontificia Universidad Católica del Ecuador, Quito, Ecuador, (4)Xishuangbanna Tropical Botanical Garden, CAS, Kunming, China, (5)Fushan Research Center, Taiwan Forestry Research Institute, Yilan, Taiwan, (6)Plant and Animal Sciences, University of Buea, Buea, Cameroon, (7)Smithsonian Tropical Research Institute, Panama, (8)Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China, (9)Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan, (10)Smithsonian Tropical Research Institute, Panamá City, Panama, (11)Center for Tropical Forest Science & Smithsonian Global Earth Observatory, Washington, DC, (12)State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China, (13)Forest Research Institute Malaysia, Kepong, Malaysia, (14)Forestry and Environment Division, Forest Research Institute Malaysia, Kepong, Malaysia, (15)Taiwan Forestry Research Institute, Taipei, Taiwan, (16)Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, Taiwan, (17)Oregon State University, Corvallis, OR, (18)South China Botanical Garden, Chinese Academy of Sciences, China, Guangzhou, China, (19)School of Life Sciences, Sun Yat-sen University, Guangzhou, China

Beta diversity captures a fundamental facet of the spatial pattern of species assemblages. Several processes can contribute to creating compositional differences among local communities, such as environmental filtering, biotic interactions and dispersal limitation. With the aim of understanding why some forests of the world exhibit higher tree beta diversity values than others, we asked: (a) What is the contribution of environmentally-related variation versus pure spatial and local stochastic variation to tree beta diversity assessed at the forest plot scale? (b) At what resolution are these beta diversity components more apparent? (c) What determines the variation in tree beta diversity observed across regions/continents? 

We compiled an unprecedented data set of ten large-scale stem-mapping forest plots differing in latitude, tree species richness and topographic variability. We assessed the tree beta diversity found within each forest plot separately. The non-directional variation in tree species composition among cells of the plot was our beta diversity measure. We compared the beta diversity of each plot to the value expected under a null model. We also apportioned the beta diversity into four components: pure topographic, spatially-structured topographic, pure spatial and unexplained. We used linear mixed models to interpret the variation of beta diversity values across the plots.


Total tree beta diversity within a forest plot decreased with increasing cell size, and increased with tree species richness and the amount of topographic variability of the plot. The topography-related component of beta diversity was correlated with the amount of topographic variability but was unrelated to its species richness. The unexplained variation was correlated with the beta diversity expected under the null model and with species richness. Because different beta diversity components have different determinants, comparisons of tree beta diversity across regions should quantify not only overall variation in species composition but also its components. Global-scale patterns in tree beta diversity are largely coupled with changes in gamma richness due to the relationship between the latter and the variation generated by local stochastic assembly processes.