Patterns of Change in Plant Leaf Functional Traits Along an Altitudinal Gradient in a Karst Climax Community

Exploring the changes in plant leaf functional traits in response to altitude across various altitudinal gradients of climax communities in karst regions can elucidate the characteristics of survival strategy adaptations among plant communities. This understanding may also reveal the growth dynamics and driving factors of climax communities in unique habitats. In this study, we examined nine climax communities located in the karst region of Southwest China, categorizing them into three distinct altitude gradients: low-, middle-, and high-altitude communities. By integrating species characteristics and community structure, we analyzed the patterns of change in leaf functional traits among plant communities at different altitudinal gradients and the relationships between these functional traits and environmental factors across the varying altitudes. The results indicated the following: (1) There was a significant difference in the specific leaf area (SLA) of the community as altitude increased, with a gradual decrease observed. The traits exhibiting higher coefficients of variation (CVs) in the leaves of the karst vertex community included the leaf carbon-to-nitrogen ratio (LCN), leaf area (LA), and leaf dry matter content (LDMC). Additionally, the environmental factors with higher CVs included soil organic carbon (SOC), soil phosphorus content (SPC), and the soil carbon-to-phosphorus ratio (SCP). (2) Soil organic carbon content (SOC), total nitrogen content (SNC), carbon-to-phosphorus ratio (SCP), and nitrogen-to-phosphorus ratio (SNP) demonstrated significant differences with increasing altitude. (3) The primary environmental factors influencing plant communities in karst areas included soil nitrogen content (SNC), mean annual temperature (NJW), soil organic carbon content (SOC), soil phosphorus content (SPC), soil water content (SWC), and mean annual precipitation (NJS). Our results indicated that the variation in leaf functional traits with altitude in karst climax communities was inconsistent. Among these traits, the specific leaf area (SLA) showed the most significant variation, and karst climax communities appeared to adapt to environmental changes by regulating traits such as leaf area (LA), leaf dry matter content (LDMC), and leaf carbon-to-nitrogen ratio (LCN). Soil organic carbon (SOC) and soil phosphorus content (SPC) are key factors contributing to habitat heterogeneity in the karst region. The karst climax communities are influenced by both soil and climatic factors along the altitudinal gradient. As altitude increases, these communities tend to adopt a life strategy. Furthermore, high-altitude terminal communities in karst areas are more susceptible to environmental filtering, while low-altitude areas are more affected by limitations in similarity.