COS 65-4
Species pool functional diversity and environmental heterogeneity jointly influence beta-diversity in temperate forests

Wednesday, August 12, 2015: 9:00 AM
323, Baltimore Convention Center
Marko J. Spasojevic, Biology, Washington University in St. Louis, St. Louis, MO
James A. Lutz, Department of Wildland Resources, Utah State University, Logan, UT
Sean M. McMahon, Smithsonian Environmental Research Center, Smithsonian Institution Global Earth Observatory, Edgewater, MD
Andrew Larson, College of Forestry & Conservation, University of Montana, Missoula, MT
Geoffrey G. Parker, Smithsonian Environmental Research Center, Edgewater, MD
Christopher Catano, Biology, Washington University in St. Louis, St. Louis, MO
Dilys Vela Díaz, Biology, Washington University in St. Louis, St. Louis, MO
Jonathan A. Myers, Washington University in St. Louis, St. Louis, MO
Benjamin L. Turner, Smithsonian Tropical Research Institute, Ancon, Panama

A key goal in ecology is to disentangle how multiple processes at different scales influence patterns of biodiversity. Variation in biodiversity can arise from local-scale niche-based processes such as competition and environmental filtering as well as from regional-scale processes such as dispersal and speciation. However, the extent to which the assembly of communities is driven by local-scale processes, regional-scale processes, or the interplay between them remains unresolved. At local scales, assembly mechanisms are often inferred from patterns of functional-trait diversity. At regional-scales, in contrast, few studies have explicitly integrated functional traits into studies of community assembly. Here, we examined patterns of beta-diversity (spatial variation in species or functional composition) across three sites that differed in regional species-pool functional diversity to partition the relative importance of local- and regional-scale processes on the assembly of woody plant communities. Within the Smithsonian ForestGeo network, we compared taxonomic and functional beta-diversity across three biogeographic regions predicted to vary in species-pool functional diversity: western coniferous forest; central deciduous forest; and eastern deciduous forest. We used a null-modeling approach to examine how environmental heterogeneity (soils & topography) and species-pool functional diversity (leaf, stem and seed traits) may jointly influence patterns of beta-diversity.


The three forests varied in environmental heterogeneity, functional beta-diversity, and species-pool functional diversity. However, environmental heterogeneity alone could not account for observed differences in functional beta-diversity among forests. Functional beta-diversity was highest in the western coniferous forest with the lowest environmental heterogeneity, and lowest in the central deciduous forest with the highest environmental heterogeneity. Moreover, species-pool functional diversity was also highest in the western coniferous forest and lowest in the central-deciduous forest, suggesting an important influence species-pool functional diversity on patterns of beta-diversity. Indeed, after accounting for differences in species-pool functional diversity with a null model, we found that patterns of beta-diversity are more similar among forests than would be predicted if beta-diversity was solely due to local environmental variation. Our results suggest that greater trait diversity at the regional scale (higher species-pool functional diversity) may increase the potential for species to partition local-scale environmental variation, leading to greater spatial variation in biodiversity (beta-diversity) within a site. Our study provides new insights into how local and regional processes jointly influence patterns of forest biodiversity and ecosystem services that depend on trait variation among co-occurring species.