Canopy Leaf Traits, Basal Area, and Age Predict Functional Patterns of Regenerating Communities in Secondary Subtropical Forests

Abstract

Secondary forests originate from natural regeneration after fallow (succession) or restoration. Species assembly in these communities, which can affect ecosystem functions and successional trajectories, is very unpredictable. Trait-based trajectories can shed light on the recovery of ecosystem functions and enable predictions of how the regenerating communities will change with forest age. Regeneration communities are affected by initial conditions and also by canopy structure and functional traits that alter dispersers' attractiveness and coexistence mechanisms. Here we evaluated how community functional traits change over time and tested if functional diversity and composition of the established canopy, as well as the structure of the canopy and forest age, influence the functional structure of regenerating tree communities when compared to their reference forests. For this, we calculated dissimilarity in trait composition (community-weighted means) and in functional diversity of regenerating communities of each succession/restoration stand, using the tree stratum of nearby mature forests as baseline values. Functional trait information comprises leaf, wood density, and reproductive traits from tree species. Our community data contain information from natural successional forests and restoration sites, in the South-Brazilian Atlantic Forest. Predictor variables of functional dissimilarities were forest age, canopy structural variables, canopy functional composition, and functional diversity. Results showed leaf traits (leaf dry matter content, leaf nitrogen content, leaf nitrogen-phosphorus ratio) and seed mass varying with forest age. Canopy functional composition based on leaf traits and total basal area significantly predicted multiple trait functional dissimilarity between the regeneration component of secondary forests and their reference community values. Dissimilarity increased when the canopy was composed of species with more acquisitive traits. Difference in functional diversity was only influenced by forest age. Mid-stage secondary forests showed lower functional diversity than early-stage forests. Our results indicated the importance of canopy traits on the natural regeneration of secondary subtropical forests. If functional similarity with reference forests is a desired objective in order to recover ecosystem functions through natural regeneration, leaf functional traits of canopy trees that establish or are planted in degraded areas must be considered in the successional processes.

Quercus wutaishanica shrub affects temperate forest community composition and soil properties under different restoration stage

“…This may be because of the existence of pioneer species in the early restoration of the Q. wutaishanica community, which recruited a large number of species, and the lack of abiotic or biotic filtration, resulting in an increase in species diversity. With restoration, the species colonization rate was higher and the mortality rate was lower in the understory, while some dominant species and herbs eventually dominated in the understory, thus changing species diversity [66]. In the present study, plant species diversity first increased and then decreased (Fig 2).…”

Tropical forest succession increases tree taxonomic and functional richness but decreases evenness

“…First, during succession, light‐demanding, early‐successional species remain present in the forest canopy (Peña‐Claros, 2003; Rüger et al., 2023) or are maintained in gaps. At the same time, the build‐up of vegetation and shading leads to the establishment of shade‐tolerant, late‐successional species with different trait values in the forest understory (Müller et al., 2021), which leads to an increase in the occupied functional trait space. Second, generally milder abiotic conditions (e.g.…”

“…Most studies that assess functional evenness or other abundance‐weighted functional diversity indices (e.g. Rhao's quadratic entropy and functional divergence) did not find any changes during succession (Bhaskar et al., 2014; Makelele et al., 2021; Müller et al., 2021; Whitfeld et al., 2014). Functional dispersion (Fdis) is the only index assessed by these studies that does show successional changes.…”

A guide to between‐community functional dissimilarity measures

“…If the CWM represents the most frequent level of a qualitative trait within a community, CWMdis can take the values 0 (agreement) or 1 (mismatch). Since CWM is commonly used for representing the trait composition of communities, the Euclidean distance between CWMs is a natural way for comparing communities, either explicitly (Müller et al 2021, Engbersen et al 2022) or implicitly as part of a linear model (Moretti et al 2013, Prieto et al 2017). Ricotta et al (2015) investigated the relatedness of the distance between CWMs with the Rao‐based approach (see therein) and showed its applicability also on phylogenetic data.…”