Perfilhamento como estratégia ecológica de espécies arbóreas: representatividade, padrões evolutivos e impacto na coleta de dados em florestas tropicais

Abstract

Resprouting, which consists of the emission of stems by trees after disturbances, is one of the most common ecological strategies in tree communities. Through resprouting, the individual increases its chances of survival by improving the resources obtaining as he has already established hydraulic and root systems. Thus, resprouting is understood as a regeneration strategy that opposes regeneration from seeds and seedlings. Although resprouting is widely present in tropical forests, little is known about its representativeness, ecological patterns, which are the main determining factors and how this strategy can influence the sampling of tree communities. Here these issues were explored in two papers. The first one explores the patterns of ecological representativeness of resprouting in dry tropical forests, also evaluating which are its main determinants (taxonomic identity vs. environment) and whether there is a phylogenetic structuring in its expression in genera (phylogenetic sign). We used two resprouting variables: the frequency, which consists of the relationship between the number of resprouted trees and the total number of individuals; and the average number of stems per tree. Our results indicate that species with low and medium resprouting frequency are the most representative species in these forests, in which it can be adopted or not as a strategy of persistence in the community due to the local restriction. We also found that resprouting variables are mainly determined by taxonomic identity, so that resprouting varies within a limit determined by the species' patterns. Finally, we did not find a phylogenetic sign for the two variables, which suggests that the phylogenetic structuring of these characteristics is mainly associated with processes of evolutionary convergence between distant lineages and evolutionary divergence between close lineages. In the second, we evaluate how methodological choices (minimum size of inclusion and method of inclusion) impact the sampling of four vegetational variables (number of trees, number of stems, biomass and species richness) in three types of tropical forests (evergreen forests, semi-deciduous and deciduous forests). For the inclusion method, we considered two methods: the by-stem method, in which the diameter of the isolated stems is considered; and the by-tree method, in which the equivalent diameter is obtained considering all of the individual's stems. Thus, in the by-tree method, stems smaller than the minimum size can be included in the sampling, if the equivalent diameter of the individual reaches the minimum size. We found that these methodological choices mainly impact deciduous and semideciduous forests, in which the adoption of the by-stem method and larger sizes of minimum diameter implies undersampling of the real ecological patterns of the number of trees, stems and species richness. In these vegetation types where resprouting is important, species may never be sampled using the by-stem method, even though they have several stems that together would reach the minimum size, if the by-tree method were adopted. Based on the results, we suggest the widespread adoption of the by-tree method and not using high minimum sizes mainly in forest types where resprouting is an important strategy.