Ecological soil C, N, and P stoichiometry of different land use patterns in the agriculture-pasture ecotone of Northern China

The way of land use affects soil nutrients and influences of stoichiometry characteristics was investigated by analyzing four different types of shallow soil (0-25 cm) taken from four different land (grazed grassland, enclosure grassland, abandoned land, farmland) in the northern piedmont of Yinshan Mountain, and the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and stoichiometry characteristics were determined. The results were as follows: (1) In general the soil was impoverished and the nutrient content was low in the study area. The soil SOC, TN, and TP were 14.57, 0.63, and 0.76 g/kg, respectively, and the AN and AP were 39.87 and 6.72 mg/kg, respectively. These five indicators showed modest variations. (2) Soil nutrient content and stoichiometry characteristics were significantly affected by land use patterns. The SOC, TN, and AN in grassland (grazed grassland and enclosure grassland) were higher than those in agricultural land (abandoned land and farmland), whereas the TP and AP were lower than those in agricultural land. The C∶N, C∶P, and C∶P ratios in grassland were higher than in agricultural land. Furthermore, the optimal fitting relationship showed that the C∶N and C∶P ratios were mainly affected by SOC, whereas the C∶P ratio was mainly affected by N, which indicated that both factors affected the C, N, and P stoichiometry characteristics in the study area soils. These results have important implications for the theoretical improvement of soil ecological stoichiometry and provide a scientific basis for constructing an ecologically functional recovery program for the fragile ecological zone located in the agriculture-pasture ecotone of northern China.