Dispersal process driving subtropical forest reassembly: evidence from functional and phylogenetic analysis

Abstract

Understanding the mechanisms of secondary succession related to forest management practices is receiving increasing attention in community ecology and biodiversity conservation. Abiotic and biotic filtering are deterministic processes driving community reassembly. A functional trait or phylogeny‐based approach predicts that environmental filtering induced by clearcut‐logging results in functional/phylogenetic clustering in younger forests, while biotic filtering (competitive exclusion) promotes functional/phylogenetic overdispersion in old‐growth forests. From this perspective, we examined the patterns of functional/phylogenetic structures using tree community data (147 species × 170 plots). These data were chronosequenced from clearcut secondary forests to old‐growth subtropical forests in the Ryukyu Archipelago, with species’ trait data (leaf and stem) and species level phylogeny. To detect clustering or overdispersion in the functional and phylogenetic structures, we calculated the standardized effect size of mean nearest trait distance and mean nearest phylogenetic distance within the plots. Functional or phylogenetic clustering was relatively weak in secondary forests, and their directional change with increasing forest age was not generally detected. Mean nearest trait/phylogenetic distance for most plots fell within the range of random expectation. The results suggest that abiotic/biotic filtering related to functional traits or phylogenetic relatedness plays a diminished role in shaping species assembly during secondary succession in the subtropical forest. Our findings of functional and phylogenetic properties might shed light on the importance of dispersal (stochastic) processes in the regional species pool during community reassembly after anthropogenic disturbance. It will also contribute to the development of coordinated schemes that maintain potential species assembly processes in the subtropical forest.

Functional traits and environmental characteristics drive the degree of competitive intransitivity in European saltmarsh plant communities

“…This latter scenario suggests that competitive intransitivity mediated by environmental filtering might increase species’ functional equivalence, possible leading to comparable species fitness and to increased probability of species coexistence. This mechanism might explain the random assortment of functional traits in subtropical forest communities in spite of strong environmental filtering (Kusumoto et al., ).…”

“…Filtering for similar traits might intensify competitive interactions, but might also give rise to intransitive competitive loops that subsequently allow species coexistence. This latter scenario suggests that competitive intransitivity subtropical forest communities in spite of strong environmental filtering (Kusumoto et al, 2016).…”

“…For example, functional traits of coexisting species are often over-dispersed in plant communities (e.g. Westoby, Falster, Moles, Vesk, & Wright, 2002;Paine, Baraloto, Chave, & Herault, 2011; but see Kusumoto et al, 2016 andGallien, 2017), and this separation of species in trait space may generate sufficient niche differentiation to permit species coexistence (Adler, Fajardo, Kleinhesselink, & Kraft, 2013). However, a different although not mutually exclusive explanation for the observed degree of coexistence is that the mix of competitively counteracting traits, such as root and shoot competition (Zhang & Lamb, 2012), or complementary resource use (Yachi & Loreau, 2007), generates a dynamic balance of competitive strength through ICNs, which allows for species coexistence in spite of high niche overlap.…”