Environmental Filtering and Disturbance Drive Multi-Dimensional Plant Diversity Across Successional Stages

Understanding how environmental factors, disturbance regimes, and successional processes jointly shape plant community structure and diversity is a central challenge in ecology, particularly under accelerating global environmental change. Traditional assessments of plant diversity have largely relied on taxonomic metrics such as species richness, which often fail to capture functional differentiation, evolutionary history, and spatial organization within communities. This limitation hampers our ability to interpret ecological processes, evaluate conservation effectiveness, and monitor ecosystem recovery. This dissertation investigates the drivers and dynamics of plant community diversity across contrasting ecosystems by integrating taxonomic, functional, phylogenetic, and spatially explicit diversity dimensions. Specifically, the study examines the combined effects of soil properties and surface-cover components on plant diversity, compares multiple diversity dimensions between strictly protected and managed forests, evaluates the sensitivity of spatially explicit compositional diversity to successional change, and assesses how post-fire forest structural dynamics influence understory diversity recovery. Results demonstrate that soil pH exerts a strong influence on species richness by shaping the species pool, with soil surface-cover components mitigating the expected negative effects of elevated soil temperature on richness. By contrast, soil moisture showed no statistically significant effect on diversity patterns. Strict protection regime does not necessarily lead to higher species richness and phylogenetic diversity, but exerts an influence on community composition, functional attributes, and the proportion of specialist species. Compositional diversity consistently captures fine-scale changes in community structure and successional dynamics that are overlooked by conventional indices; importantly, it exhibits a stable and directional response along forest successional gradients, underscoring its robustness and potential as an indicator for monitoring forest succession. Moreover, forest structural heterogeneity emerges as a key mediator linking disturbance history to understory diversity. Taken together, these results reveal that plant community assembly is governed by the interaction between strong environmental filtering and disturbance-driven structural heterogeneity, operating across fine spatial scales and successional stages. By integrating multiple diversity dimensions, this dissertation demonstrates that different metrics capture complementary aspects of community dynamics, highlighting the limitations of relying solely on species richness. This integrative framework provides a more comprehensive understanding of biodiversity patterns and offers a robust basis for evaluating conservation strategies, monitoring ecosystem recovery, and guiding biodiversity management under changing environmental conditions.