Ecological Stoichiometry of Multiple Nutrients in Leymus chinensis and Soils Subjected to Long-Term Saline-Sodic Stress in Western Jilin Province, China

L. chinensis is considered an important plant for saline-sodic soil restoration. Ecological stoichiometry of multiple nutrient elements in Leymus chinensis (L. chinensis) and soils subjected to long-term saline-sodic stress remains unclear, which hinders our understanding of the mechanisms regulating nutrient cycling in the plant-soil environment. We examined nutrient element levels in saline-sodic soil and L. chinensis in western Jilin Province. Soil analysis revealed medium to high levels of available N, K, P, Mo, Mn, Fe, Cu, and Zn. The Mn/Fe and N/P ratios exceeded the national soil average of China, while those of Fe/Cu, Fe/Zn, and P/K were comparatively lower. Furthermore, L. chinensis exhibited deficiencies in the Mn, Zn, and P. Mo/Mn, Mo/Zn, and Fe/Zn ratios, which were significantly higher compared to healthy plants, while Mn/Fe and P/K showed the opposite trend. Soil pH had the most significant effect on element stoichiometry in both the soil and in L. chinensis. Particularly, the soil available Mn, Zn, K, along with L. chinensis Mn, Fe, Cu, and P levels exhibited sensitivity to pH fluctuations. Additionally, we observed significant synergistic or antagonistic effects between the soil available element concentration and stoichiometry ratios. Among these, only Mn, Fe, Fe/Zn, Mo/Zn, N/K, and Mo/Fe in L. chinensis were significantly modeled (P < 0.05). The Mo/Fe homeostasis index was the lowest at 0.97, followed by Fe (1.16), N/K (2.28), Mo/Zn (2.59), Fe/Zn (3.38), and Mn (4.92), while other elements and their stoichiometric ratios remained stable. Overall, L. chinensis, as the dominant species in saline-sodic soil, demonstrated high homeostasis.