Determinants of species abundance for eastern North American trees

Authors

  • Dingliang Xing,

    1. State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
    2. University of Chinese Academy of Sciences, Beijing, China
    Search for more papers by this author
  • Nathan G. Swenson,

    1. Department of Plant Biology, Michigan State University, East Lansing, MI, USA
    Search for more papers by this author
  • Michael D. Weiser,

    1. Department of Biology, University of Oklahoma, Norman, OK, USA
    Search for more papers by this author
  • Zhanqing Hao

    Corresponding author
    1. State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
    • Correspondence: Zhanqing Hao, State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China.

      E-mail: hzq@iae.ac.cn

    Search for more papers by this author

Abstract

Aim

We aimed to quantify the relative contributions of trait-based selection and the flow of individuals across space created by differences in species abundance, i.e. mass effects, in determining local-scale species relative abundance (SRA) at 0.07 ha, 1° grid cell and subregion grains.

Location

The eastern USA.

Methods

We coupled a maximum entropy model (MaxEnt) with nine species-specific plant traits and a continental-scale forest inventory dataset to perform our analyses. Mass effects were estimated using the next grain size up as the metacommunity (or the eastern USA at the subregion grain, and also at the 1° grid cell grain in a fourth analysis). Permutation tests were conducted to test the significance of trait constraints. The Kullback–Leibler divergence index was used to decompose the information content in each assemblage SRA.

Results

Trait constraints were significant in predicting community structures at coarse scales, but were largely not significant at fine or medium scales. At the 0.07 ha grain little of the variation in local SRA can be explained by either trait constraints or a regional SRA. At the 1° grain c. 61% of the variation could be accounted for by a regional SRA represented by subregions. At the subregion grain c. 74% of the variation could be accounted for by trait constraints and the SRA of the entire study area.

Main conclusions

Our results suggest that the relative importance of community assembly processes is scale dependent. Estimated mass effects predominated at small spatial scales where environmental gradients were weak. Trait-based selection was hard to detect at small scales and was strongest at large scales where environmental gradients are stronger. The fact that, at all scales, mass effects accounted for more variation in assemblage SRA than trait-based selection in our analyses suggests that regional processes are important in determining community structures more locally.

Ancillary