The purpose of this study was to explore the spatial distribution of soil carbon, nitrogen and phosphorus in different plant communities in Baiyu mountain areas and the vertical distribution of their ecological stoichiometric characteristics, to reveal the nutrient characteristics of different plant communities, and provide scientific information for ecological management and vegetation restoration.

In this study, barren grassland, Medicago sativa grassland, Pinus tabuliformis, Ulmus macrocarpa, and Hippophae rhamnoides tree-shrub forest land were used as the research objects. At the same time, the differences in soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) content and stoichiometric ratio indicators of five typical plant communities in the 0-60 cm soil layer were analyzed.

(1) The soil nutrient contents in different plant communities decreased with the increase of soil depth, with a surface aggregation effect, which showed “arbor forest land > shrub land > grassland”. (2) Plant type and soil depth has certain effects on soil C, N, P contents and stoichiometric ratio, while their interaction effect was not significant, and the limiting degree was plant community > soil depth. (3) The soil C, N, P, C/P and N/P were much lower than those of the national average, and the C/N value was close to or higher than the average values of terrestrial and forest soils in China, which showed that soil P was relatively sufficient compared with other elements, the soil organic carbon sequestration capacity in this area was low, and plant growth was more susceptible to nitrogen limitation compared with other elements. (4) The correlations between N and N/P, and N/P, C/P and C were extremely significant (P < 0.001), and the correlation between C and N was extremely significant (P < 0.001). The correlation coefficient between P content and each index was small, and the correlation was weak. In different soil layers, N had the greatest impact on the PCA1 axis, indicating that the soil in the study area was mainly affected by SOC and TN, while N played a key role in the regulation of the relationship between N and P, and C also had a great influence on N, P and their stoichiometric ratios.

Compared with other elements, the soil P in Baiyu mountain areas is relatively sufficient, and the organic C sequestration capacity is low. The soil in this area is mainly affected by C and N, and the influence degree is N > C. Therefore, in practical production, artificial measures such as rain harvesting and afforestation and tree classification can be adopted to improve soil physicochemical properties and better promote the ecosystem nutrient cycling according to local conditions.