This study investigated the ecological stoichiometric characteristics of the plant-litter-soil continuum, as well as nutrient resorption and utilization efficiency, in mixed communities of Luo mountain, Ningxia, to reveal the nutrient allocation and utilization strategies, and to provide a scientific foundation for vegetation protection and sustainable management in this region.

Four typical mixed communities were investigated: mixed alpine shrub community, mixed low-mountain shrub community, mixed coniferous community and mixed conifer-broadleaf community. This study systematically analyzed the differences in C, N, P contents, and stoichiometric ratios across plant organs, litter and soil. It quantified their coupling relationships, homeostasis, resorption and utilization efficiencies of C, N, and P nutrients.

1) Across all communities, the C content was lowest in roots, while the N and P contents were the highest in leaves. The C/N was the lowest in leaves; The C/P was the highest in branches; And the N/P was the lowest in roots. In addition, the plant P content was lower in the two shrub mixed communities compared to the two tree mixed communities, while the C/P and N/P were higher; 2) The litter C/N of the mixed conifer-broadleaf community was significantly higher than that in the mixed alpine shrub community (F=7.72, P<0.05); 3) Soil C and C/P (F=33.44, P<0.05; F=47.64, P<0.05) in the two mixed tree communities, and soil N and N/P (F=17.76, P<0.05; F=55.00, P<0.05) in the mixed coniferous community were all significantly higher than in the two mixed shrub communities; 4) Significant positive correlations were found in P content across plant organs, litter, and soil (P<0.05). Position and aspect significantly influenced ecological stoichiometric characteristics. The homeostasis of P, C/P, and N/P in leaves, branches, and roots was found to be sensitive; 5) The N and P reabsorption efficiency was stronger in the two mixed tree communities compared to the two mixed shrub communities. The nutrient utilization efficiency of P was higher than that of N and C across all communities.

Plant growth in mixed shrub communities was P-limited, while mixed tree communities were N-limited. P exhibited strong interconnections among components and higher utilization efficiency.