新疆北部六种草地类型土壤碳氮磷生态化学计量特征

Spatial variations in soil carbon, nitrogen, and phosphorus concentration, as well as their ecological stoichiometry, in grasslands are related to the function and stability of grassland ecosystems. The Irtysh River Basin features a significant disparity in altitude, notable climate variation, and diverse grassland types that display a vertical zonal distribution. However, the influence of altitude, climate, soil properties, and vegetation on the spatial patterns of soil carbon, nitrogen, and phosphorus stoichiometry in the Irtysh River Basin, which is a typical pastoral area in Xinjiang, has not been fully understood. This study investigated 65 sample points from six main grassland types (temperate desert, temperate desert steppe, temperate steppe, temperate meadow steppe, mountain meadow, alpine meadow) in the Irtysh River Basin, at depths of 0-10 cm and 10-20 cm. The results were as follows: (1) The soil organic carbon (39.06-62.59 gkg-1), total nitrogen (3.87-6.95 gkg-1), and total phosphorus concentration (0.53-1.59 gkg-1) of alpine meadow, mountain meadow, and temperate meadow steppe were higher than the average values of Chinese soil (24.56 gkg-11.88 gkg-10.56 gkg-1). However, the soil C : N (5.03-9.97) and C : P ratios (7.50-52.38) of six grassland types were lower than the average values of Chinese or global soil, as well as the soil N: P ratios (1.53-3.72) of temperate steppe, temperate desert steppe, and temperate desert (11.4064.303.90). (2) The concentrations of soil carbon, nitrogen, and phosphorus, as well as C : N and C : P ratios, increased significantly with increasing altitude (328-2655 m), precipitation and decreasing temperature. These parameters also showed significant correlations with soil physicochemical properties and vegetation characteristics. With increasing altitude and precipitation, and decreasing temperature, the differences in soil carbon and nitrogen concentration, and soil C : P ratios gradually increased among soil layers. (3) The results of the structural equation model (SEM) showed that altitude and climate factors had the highest impact on soil carbon, nitrogen, and phosphorus concentration, as well as their ecological stoichiometry. Altitude affected soil carbon, nitrogen, and phosphorus concentration by changing temperature, precipitation, vegetation characteristics, and soil physicochemical properties, ultimately affecting ecological stoichiometry. Future research should further investigate the impact of climate change on soil carbon, nitrogen, and phosphorus concentration, as well as on their ecological stoichiometry, at a regional scale. This paper provides basic data and a theoretical basis for estimating soil nutrient storage, as well as for the protection and utilization of grassland ecosystems in the Irtysh River Basin.