Multifractal analysis of species diversity and phylogenetic diversity in south subtropical evergreen broad-leaved forests

Patterns of species diversity and phylogenetic diversity at the community level are a major focus of current ecological research, and correctly revealing the scale effects of these patterns is of great significance for characterizing their spatial distributions and understanding the mechanisms of biodiversity formation. Traditional ecological methods cannot accurately describe the cross-scale complexity of species' spatial distribution patterns, but fractals are an excellent tool for explaining complex structures and scale effects. However, traditional fractal analysis only uses a single fractal dimension, which is not enough to comprehensively describe the fractal characteristics of community diversity patterns. Multifractal analysis, which consists of a series of spectral lines composed of fractal dimensions that express the fractal characteristics of species, is a better method for quantitatively describing the complexity of species diversity patterns and spectral diversity patterns in forest communities, as well as for deepening our understanding of the roles that ecological processes play at different scales. Therefore, multifractal analysis has incomparable advantages over traditional fractal analysis. Although multifractal analysis of species diversity provides some insights into diversity patterns, it is limited by the fact that it only considers the relative abundance of species and not the length of their evolutionary history, so it does not truly characterize interspecific differences. In order to more comprehensively understand the characteristics of community diversity patterns, it will be necessary to apply multifractal analysis to phylogenetic diversity patterns. In this study, we selected a sample plot 20 hm2 in size in the Dinghushan Nature Reserve, Guangdong Province, and we used the multifractal method to study the diversity patterns of species and phylogeny in the plot. The results showed that: (1) The spatial distribution patterns of species diversity and phylogenetic diversity in the South Asian tropical broad-leaved evergreen forest community were characterized by multiple fractals at the local scale. The spatial distributions of the dominant and rare species groups in the community were not uniform. (2) The richness and length of evolutionary history of the very dominant species group in the South Asian tropical broad-leaved evergreen forest community showed a decreasing trend, the length of evolutionary history of the very rare species group showed a decreasing trend, and the rate of change of its richness showed a decreasing trend, which may have been due to the influence of the altitudinal gradient, where an increase in altitude negatively impacts species richness and phylogenetic diversity. (3) The spatial distribution pattern of species described by the multifractal analysis of phylogenetic diversity was more detailed than that depicted by the multifractal analysis of species diversity, and this was mainly reflected in the characterization of the changes in the richness of the very rare species group and the length of evolutionary history. Multifractal analysis provides us with a convenient way to describe the composition and spatial pattern of community species groups, effectively revealing the patterns of species diversity and phylogenetic diversity in forest communities. This finding is of great significance for the conservation of species, showing their important contributions to the ecosystem and to the maintenance of ecosystem stability.