Examining the stoichiometry of C:N:P:K in the dynamics of foliar-litter-soil within dominant tree species across different altitudes in southern China

Ecological stoichiometry assessment provides insight into the interactions between foliar-litter-soil dynamics among dominant tree species and facilitates their conservation. However, little research has been carried out on such trends within mixed forest ecosystems in national forest nature reserves globally. The present study fills this knowledge gap by examining the ecological stoichiometry of dominant tree species at various altitudes in desirable nature reserves in southern China. This study concentrates on six representative plant communities, each pivotal in maintaining carbon (C), nitrogen (N), phosphorus (P), and potassium (K) balances, along with energy flows. The selected communities encompass two plantations comprising Cunninghamia lanceolata and Phyllostachys edulis and four natural forests, including evergreen broad-leaved forest (Manglietia conifera), evergreen deciduous broad-leaved mixed forest (Daphniphyllum macropodum and Acer davidii), deciduous broad-leaved forest consisting of Fagus longipetiolata, and coniferous forest (Tsuga chinensis). Furthermore, this study involved the measurement of C, N, P, and K contents in foliage, litter, and soil. The outcomes revealed significant variations in foliar, litter, and soil contents and stoichiometric attributes across dominant plant communities. Correlation analysis highlighted substantial positive associations between N and P contents in foliar and litter components, while soil N and P contents exhibited insignificance. Broad-leaved forests generally displayed higher leaf N and P contents compared to coniferous forests. However, exceptions observed in the N content of M. conifera and the P content of D. macropodum and F. longipetiolata. The high-altitude T. chinensis forest exhibited one of the highest ecological litter and soil ratios. Notably, T. chinensis soil demonstrated richness in N but deficiency in K, impacting foliar growth by limiting N and K availability. Additionally, the low N and P contents in litter hindered decomposition. Furthermore, the nutrient content and ratios of other nutrients remained relatively stable except for soil K and plant K, soil C: K, and litter C: K, which were consistent with homeostasis theory. These findings provide scientific evidence for nutrient cycle regulation, ecosystem protection, and valuable insights into complex ecological relationships in mixed forests.