Species Rarity and Topography Determine the Plant Functional Structure Along the Successional Pathway in Heterogeneous Degraded Karst Forests

Abstract

Understanding the dynamics of plant functional community structure along the successional pathway is crucial for natural resource conservation and environmental management, especially in those specially degraded ecosystems. This study established forest dynamic plots along the successional pathway in degraded karst forests to measure six plant functional traits: specific leaf area, leaf dry matter content, leaf thickness, leaf carbon content, leaf nitrogen content, and leaf phosphorus content. By implementing Grime's CSR strategy and employing a ternary functional diversity diagram framework, the variations in ternary plant ecological strategies and functional diversity were quantified. The results showed that the plants with competitive strategies increased along the succession, while plants with S-strategy decreased. The functional diversity declined from the early- to mid-successional stages, followed by an increase in the late-successional stage, with a corresponding inverse trend in functional redundancy. Furthermore, there was a decrease in species dominance from the early- to mid-successional stage, which contributed to the trade-off between functional diversity and redundancy. The topographic roughness and soil pH value were the main abiotic factors determining the variation in functional diversity among successional stages. Species rarity positively impacted functional diversity but negatively affected functional redundancy, highlighting the role of rare species in maintaining ecosystem functionality and emphasizing the vulnerability of karst ecosystems to environmental changes. This study provides valuable insights into the successional mechanisms in karst forests, thereby facilitating the development of effective conservation and environmental management.