Organization of Forest Understory Communities: Species Diversity, Taxonomic Distinctness, and Vertical Structure

Understanding the organization of forest understory communities is essential for deciphering ecosystem assembly mechanisms. This study evaluates understory plant communities through an integrated characterization of species diversity, taxonomic distinctness, and the vertical structure of plant height. Sampling was conducted across 17 plots (10 subplots each), where flora was inventoried and plant heights were measured. Based on these data, ten diversity and functional-structural indices were calculated, and community variability was assessed via multivariate analyses. Results show that species diversity is strongly associated with abundance evenness, whereas total abundance and species richness exhibit independent variation, playing no role in the spatial differentiation of communities. Taxonomic distinctness revealed a broad taxonomic spectrum (species from phylogenetically distant families and orders) and pronounced heterogeneity, with these indices being independent of species diversity. Plant height structure varies considerably, ranging from monotypic communities dominated by Carex pilosa to highly heterogeneous associations where low vernal species, tall megaforbs, and natural regeneration co-occur. Principal component analysis (PCA) demonstrated that PA1 (52.91%) defines the species diversity, evenness, and vertical structure gradient, while PA2 (18.93%) indicates an independent taxonomic and phylogenetic gradient, providing a robust perspective on understory complexity.