Ecological drivers of spatial community dissimilarity, species replacement and species nestedness across temperate forests
Funding information: National Natural Science Foundation of China, Grant/Award Number: 31722010 and 31770666; Chinese Academy of Sciences, Grant/Award Number: XDPB0203; National Key Research and Development Program of China, Grant/Award Number: 2016YFC0500300; Smithsonian Global Earth Observatory Initiative; HSBC Climate Partnership; International Center for Advanced Renewable Energy and Sustainability; National Science Foundation, Grant/Award Number: DEB 1557094; Tyson Research Center; The 1923 Fund; Cofrin Center for Biodiversity; European Research Council (ERC), Grant/Award Number: 233066
Abstract
Aims
Patterns of spatial community dissimilarity have inspired a large body of theory in ecology and biogeography. Yet key gaps remain in our understanding of the local‐scale ecological processes underlying species replacement and species nestedness, the two fundamental components of spatial community dissimilarity. Here, we examined the relative influence of dispersal limitation, habitat filtering and interspecific species interactions on local‐scale patterns of the replacement and nestedness components in eight stem‐mapped temperate forest mega‐plots at different ontogenetic stages (large versus small trees).
Location
Eight large (20–35 ha), fully mapped temperate forest plots in northern China and northern U.S.A.
Time period
2004–2016.
Major taxa studied
Woody plants.
Methods
We combined decomposition of community dissimilarity (based on the Ružička index) and spatial point‐pattern analysis to compare the spatial (i.e., distance‐dependent) replacement and nestedness components of each plot with that expected under five spatially explicit null models representing different hypotheses on community‐assembly mechanisms.
Results
Our analyses revealed complex results. In all eight forests, spatial community dissimilarity was best explained by species replacement among local tree assemblages and by a null model based on dispersal limitation. In contrast, spatial nestedness for large and small trees was best explained by random placement and habitat filtering, respectively, in addition to dispersal limitation. However, interspecific interactions did not contribute to local replacement and nestedness.
Main conclusions
Species replacement is the predominant process accounting for spatial community dissimilarity in these temperate forests and caused largely by local‐scale species clustering associated with dispersal limitation. Nestedness, in contrast, is less prevalent and primarily associated with larger variation in local species richness as caused by spatial richness gradients or ‘hotspots’ of local species richness. The novel use of replacement and nestedness measures in point pattern analysis is a promising approach to assess local‐scale biodiversity patterns and to explore their causes.
