Analysis of species pair associations combined with functional traits reveals the effects of environmental filtering and biotic interactions in an unmanaged temperate forest

We investigated the drivers of interspecific spatial associations among forest woody species by analysing how environmental filtering, hierarchical competition, limiting similarity and colonisation effects shape functional trait distributions and vary with successional stage.

The study was conducted in a 3.8‐ha temperate forest established through natural recolonisation in an urban setting in Brussels, Belgium.

We mapped all trees ≥1.3 m in height, characterised 22 functional traits for the 27 most abundant species, and quantified 25 environmental variables. Pairwise spatial associations were related to functional and environmental distances using an innovative analytical framework.

Environmental filtering is the strongest driver of species associations in this forest, but it interacts with hierarchical competition. Limiting similarity has a minor influence on species co‐occurrence patterns. Colonisation effects obscure the signals of environmental filtering and hierarchical competition and artificially reinforce those of limiting similarity. Additionally, species pair associations are linked to successional stages.

Combining interspecific spatial associations, functional traits and successional strategies provides a robust framework to disentangle species assemblage mechanisms in natural forests.