Soil Nutrients and Ecological Stoichiometry Under Different Land Use Types in the Western Songnen Plain in China

Understanding soil nutrients and stoichiometry across land-use types is essential for semiarid ecosystem management. We selected 130 sampling sites across four land-use types (dryland, paddy field, grassland, and forestland) in the Western Songnen Plain of China. We measured soil pH, nutrients (SOC, TN, TP, TK, and TS), trace elements (Mn, Zn, Cu, F, Se, and Cl), and oxides (MgO, CaO, Fe2O3, SiO2, and TiO2). One-way analysis of variance (ANOVA), Pearson correlation analysis, and redundancy analysis (RDA) were used to assess nutrient concentrations, stoichiometric ratios, and their environmental drivers. Our results showed that soils were generally alkaline, with the highest pH in grassland. Dryland had significantly higher SOC (12.47 g/kg), TN (1.05 g/kg), and TP (0.22 g/kg) than grassland (9.58, 0.79, and 0.19 g/kg, respectively). Forestland had the highest TK (23.18 g/kg). Most total nutrient concentrations were positively correlated with trace-element concentrations, except for TK. The C:N of paddy field (12.38) was significantly lower than those of grassland (14.24) and forestland (14.42), while both N:P (10.92) and N:K (0.13) were significantly higher than those in grassland (8.63, 0.11). The P:K of dryland (0.0137) was significantly higher than those in grassland (0.0108) and forestland soils (0.0106). RDA identified SOC and TP as common major factors associated with variation in nutrient stoichiometry, explaining 96.1%, 34.8%, 94.1%, and 93.2% of the variation in dryland, paddy field, grassland, and forestland, respectively. In addition, trace elements and oxides also explained the variation to varying degrees. This study provides a basis for sustainable land-use management in semiarid regions.