Leaf–Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry and Adaptation in Karst Plant Communities

In order to elucidate the factors regulating nutrient dynamics in plant–soil interactions across various latitudes within the karst climax community, this study focused on the karst forest climax community in Guizhou Province, Southwest China. We analyzed and compared the differences in carbon, nitrogen, and phosphorus content, as well as stoichiometry, in plant leaves and soils under various growing conditions. Additionally, redundancy analyses were conducted to investigate the stoichiometric correlations between plants and soil. The research findings indicate the following: (1) Leaf carbon content (LCC) and the carbon-to-nitrogen ratio (LCN) exhibit significant differences across various latitudes, with the lowest values observed in high-latitude regions. (2) Soil organic carbon (SOC) and the carbon-to-nitrogen ratio (SCN) also show significant variations across latitudes, with the lowest concentrations found in high-latitude regions and the highest in low-latitude regions. (3) The variability in leaf nutrient element ratios among karst region climax communities is greatest in low-latitude areas. This study found that the carbon content (LCC), nitrogen content (LNC), and carbon-to-nitrogen ratio (LCN) of leaves in karst climax community plants decrease as latitude increases. This suggests that plants regulate the nutrient utilization efficiency of carbon content (LCC), nitrogen content (LNC), and phosphorus content (LPC) in their leaves to maintain the nutrients necessary for their growth and development along the latitudinal gradient. The sensitivity of soil organic carbon (SOC), carbon-to-nitrogen (SCN), and carbon-to-phosphorus (SCP) ratios to latitudinal changes were particularly pronounced in the karst climax community. Additionally, plant leaf stoichiometry was significantly influenced by soil phosphorus content (SPC) in mid- and high-latitude regions, while factors other than soil nitrogen content (SNC) had a more substantial impact on plant leaf stoichiometry in low-latitude areas. The findings of this study are highly significant for guiding nutrient management in karst forest ecosystems and for the restoration of degraded karst forest vegetation.