Understory herbaceous plants are an important component of forest ecosystems, playing important roles in species diversity and forest dynamics in forests. However, the current understanding of the biodiversity of forest communities is mostly from woody plants, and knowledge of community structure and species diversity for understory herbaceous plants remains scarce. In a subtropical forest in China, we investigated understory vascular herbaceous diversity from 300 plots (5 × 5 m) in the main growing season. In this study, we analyzed the community structure and diversity pattern of the understory herbaceous community and linked the species diversity pattern to both abiotic and biotic environments. We found a rich diversity of understory herbaceous communities in this forest (81 species belonging to 55 genera), and floristic elements at the genus level were dominated by tropical elements, followed by temperate elements. The diversity pattern of the understory herbaceous showed a significant habitat preference, with the highest diversity in the lowland valleys and then followed by in middle slopes. In addition, herbaceous diversity was significantly affected by both abiotic factors (such as terrain convexity) and biotic factors (such as the diversity of surrounding woody plants). Our study indicated that species diversity of understory herbaceous showed a remarkable habitat preference, such as lowland valleys, and highlighted the importance of both abiotic and biotic environments in driving herbaceous diversity patterns in the subtropical forest understory.

“Interspecific associations” refers to the interrelationship among different species in a particular spatial distribution, which plays an important role in species distribution, community assembly, and responses to environmental changes. However, the strength and/or direction of interspecific associations may vary with environmental gradients and scales. To understand the effects of habitat types and research scales on interspecific associations in subtropical forests, we modeled the interspecific associations for more than 15,000 individuals representing 74 co-occurring species from three habitat types and three scales by using the variance ratio and the Spearman rank correlation coefficient. We found that overall interspecific associations at a community level exhibited significant positive associations for most habitat types and scales. Moreover, interspecific associations of pairwise species have strong habitat dependence, and the association strengths decreased with the increase in elevation (change in habitat types). However, the scale dependence of pairwise interspecific associations varies with habitat types. The strength of interspecific associations increased with the increasing scales (10 m × 10 m, 20 m × 20 m, and 40 m × 40 m) at low-valleys and mid-hillside habitats, while the scale-dependent effect was not detected at high-ridges. In conclusion, our study highlights the importance of environmental gradients and research scales on interspecific associations in diverse subtropical forests, and environmental gradients and research scales should be considered in future studies.

Temporal change of beta diversity provides a better understanding of the extent and consequences of species composition in forest communities with the ongoing global climate change. However, relatively little is known about temporal beta diversity changes across vertical stratification in the forest. In this study, we divided more than 5,000 tree individuals from a mixed broadleaf-conifer forest into four vertical strata (i.e., shrub, subcanopy, lower canopy, and upper canopy) to quantify how vertical stratification drives the temporal change of taxonomic and phylogenetic beta diversity. We found that taxonomic beta diversity significantly decreased while phylogenetic beta diversity showed an insignificant increase after 5 years. When considering vertical stratification, taxonomic beta diversity in the subcanopy, lower canopy, and upper canopy significantly changed with inconsistent directions, but phylogenetic beta diversity in the shrub significantly increased. Moreover, the significant decrease in taxonomic beta diversity is mainly driven by changes in species composition in shrub and subcanopy stratification (with 85.89% contributions). The changes in phylogenetic beta diversity are driven by shifts in the shrub and upper canopy (with 96.02% contributions). Our study suggests that taking community vertical stratification into consideration contributes to a better understanding of temporal beta diversity in forest communities.

Extreme climatic events are predicted to increase in frequency and magnitude as global climate change continues. Extreme climatic events have profound impacts on community structure and dynamics, but their effects on the dominant species within a community remains unclear. To explore this issue, we analyzed changes in population dynamics and dead individuals’ spatial pattern for several dominant species (Castanopsis eyrei, Schima superba, Pinus massoniana, and Daphniphyllum oldhamii) among different habitats in a subtropical forest before and after a significant winter storm that occurred in February 2008. Using the Gutianshan 24-ha forest plot as a representative sample, we found that the plot-level DBH of P. massoniana and C. eyrei significantly increased after the winter storm, while the plot-level basal area of P. massoniana and S. superba decreased significantly. In addition, P. massoniana was most affected by the storm (mortality: 9.08%; population change rate: −8.93%), followed by C. eyrei (mortality: 6.93%; population change rate: −4.91%). Small-diameter individuals experienced higher mortality rates, but the diameter structure of the dominant species at the population level remained basically stable. The number of individuals, the density of the dominant population, the number of mortalities, and the mortality rate of the dominant species differed among habitats. The spatial point patterns of the dead individuals at each life stage were mainly aggregated in distribution, and the degree of aggregation tended to decrease with increasing scale. In conclusion, the population dynamics of dominant species were significantly altered following the winter storm, but the extent of the changes varied with species. Our study suggests that analyzing the dominant species of a community contributes to a better understanding of the biological response of forest ecosystems in the face of extreme climatic events.

Biological invasions threaten biodiversity and ecosystem stability through stage-dependent functional trait mediation. However, the mechanistic linkages between invasion intensity and multidimensional functional traits remain inadequately characterized. To address this gap, we analyzed eight multidimensional functional traits across 290 subtropical herbaceous plots in Jinhua, China. By integrating invasion level, we evaluated how native and invasive species traits differentially regulate community invasibility, a metric quantifying a community’s susceptibility to biological invasion. Functional and taxonomic diversity exhibited hump-shaped patterns, peaking at moderate invasion before declining sharply under heavy invasion, while community invasibility increased markedly with invasion level. Native communities resisted invasion through persistent suppression of canopy height and stage-adaptive strategies: Leaf thickness emerged as a critical resistance trait under heavy invasion, counteracting invasive dominance. In contrast, invasive species initially prioritized rapid canopy occupation via height-mediated advantages, subsequently shifting toward stress tolerance (e.g., thickened leaves) and resource reallocation (e.g., root-shoot ratio adjustments) to consolidate dominance. Native abundance universally suppressed invasibility across all invasion stages, whereas invasive abundance amplified success only at advanced stages. Resistance was governed by stage-dependent trait trade-offs: Native leaf dry weight enhanced invasibility under light invasion but became ineffective as competition intensified. Conversely, invasive aboveground biomass and root-shoot ratio consistently promoted invasibility, reflecting prioritization of rapid resource acquisition. Our findings demonstrate that invasion outcomes depend on the spatiotemporal coordination of multidimensional functional traits. We propose an adaptive management framework for urban ecosystems emphasizing structural preservation (e.g., maintaining native canopy height) combined with stage-specific trait optimization of resistance traits to mitigate invasibility.

Anthropogenic disturbances significantly impact plant biodiversity in subtropical forests. While prior research has primarily concentrated on taxonomic diversity, other dimensions of biodiversity, such as phylogenetic and functional diversities, remain insufficiently explored. This study simultaneously investigated these three facets of plant diversity in subtropical forests with two distinct disturbance histories in eastern China, aiming to elucidate the effects of intermediate anthropogenic disturbances on biodiversity. Disturbed deciduous broadleaf forests exhibited markedly lower Pielou evenness index values compared to their conserved counterparts (p < 0.05). Disturbed evergreen broadleaf forests demonstrated significantly higher species richness, Shannon–Wiener index scores, and phylogenetic diversity relative to those found in conserved forests (p < 0.05). Furthermore, both disturbed deciduous broadleaf and mixed evergreen–deciduous broadleaf forests displayed significantly reduced functional richness and quadratic entropy coefficient values when compared with their conserved equivalents (p < 0.05). Forest type exerted a significant influence on all three dimensions of biodiversity (p < 0.05). In conclusion, intermediate anthropogenic disturbances have the potential to enhance both plant taxonomic and phylogenetic diversities while concurrently diminishing functional diversity within the subtropical forests of eastern China. The mechanisms driving responses in plant diversity to intermediate anthropogenic disturbances vary according to forest types.