A permutation test and spatial cross-validation approach to assess models of interspecific competition between trees

• Published in: PloS one Vol. 15; no. 3; p. e0229930
• Main Authors: Allen, David, Kim, Albert Y.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11.03.2020; Public Library of Science (PLoS)
• Subjects: Analysis; Bayes Theorem; Bayesian analysis; Biology and Life Sciences; Censuses; Competition; Computer and Information Sciences; Ecology and Environmental Sciences; Ecosystem; Estimation; Forest ecosystems; Forests; Growth models; Identity; Interspecific; Mathematical models; Neighborhoods; Permutations; Phylogenetics; Phylogeny; Physical Sciences; Plant communities; Plant populations; Population Dynamics; Regression analysis; Regression models; Research and Analysis Methods; Setting (Literature); Species; Species Specificity; Tree growth; Trees; Trees - growth & development; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0229930

Measuring species-specific competitive interactions is key to understanding plant communities. Repeat censused large forest dynamics plots offer an ideal setting to measure these interactions by estimating the species-specific competitive effect on neighboring tree growth. Estimating these interaction values can be difficult, however, because the number of them grows with the square of the number of species. Furthermore, confidence in the estimates can be overestimated if any spatial structure of model errors is not considered. Here we measured these interactions in a forest dynamics plot in a transitional oak-hickory forest. We analytically fit Bayesian linear regression models of annual tree radial growth as a function of that tree's species, its size, and its neighboring trees. We then compared these models to test whether the identity of a tree's neighbors matters and if so at what level: based on trait grouping, based on phylogenetic family, or based on species. We used a spatial cross-validation scheme to better estimate model errors while avoiding potentially over-fitting our models. Since our model is analytically solvable we can rapidly evaluate it, which allows our proposed cross-validation scheme to be computationally feasible. We found that the identity of the focal and competitor trees mattered for competitive interactions, but surprisingly, identity mattered at the family rather than species-level.