Do the distribution patterns of plant functional traits change during early secondary succession in tropical montane cloud forests?

Abstract

Several ecological processes intervene in the assembling of plant communities, such as environmental filtering and biotic interactions (e.g., competition, facilitation). The analysis of the distribution of the functional traits of plants helps to identify which of these processes is involved in the succession of a plant community assembly. We analyzed the distribution patterns of two groups of functional traits in a chronosequence spanning the first 40 years of secondary succession (SS) of a plant community of the tropical montane cloud forest (TMCF). One group of traits (leaf area, leaf thickness, leaf phosphorous and leaf nitrogen) is associated to the resource-acquisition strategy, and the second group to the conservation strategy (wood density, leaf dry mass per area unit, leaf density and leaf carbon). For each group, two multi-trait indices were quantified, namely functional divergence and dispersion. The number of individuals per plot was randomized in order to produce a null model and analyze the simulated index-distribution patterns. Then, the standardized size effect (SES) was calculated. Our results showed that both, divergence and dispersion, decreased towards the end of the successional gradient, leading to convergent patterns in the conservation traits group. The SES acquired negative values, which suggests that convergent patterns may be driven by environmental filtering. Functional diversity showed a tendency to decrease even when a species turnover between successional stages had occurred (ANOSIM, R Global = 0.64, P = 0.01). The dominance of Oreomunnea mexicana, at the end of the chronosequence, may have a particularly important role in the observed functional convergence.