关键词: 土壤有机碳密度(SOCD), 全氮密度(TND), 土地利用类型, 土壤质地, 植被退化

Abstract: The authors collected soil samples from 94 profiles in Inner Mongolia covering 4 land use types: cropland, abandoned cropland, artificial forest and steppe, in which steppe can be further classified into sandy steppe and non-sandy steppe. It is found that soil organic carbon density (SOCD) is affected by soil texture. It increases with the content of clay (<2m), fine silt (2-16m) and coarse silt (16-63m). However, total nitrogen density (TND) is affected both by soil texture and land use types. Non-sandy steppe has the highest TND. Cultivation leads to the decreasing of TND but not SOCD. The expected increase in SOCD of artificial forest does not realize. Since the requirement of soil nutrient and water is large, artificial forest may even cause strong negative effects on soil fertility and sustainability. It is also found that soil nutrient decreases when mean annual temperature (MAT) increases. Under global warming, the region may turn to an important carbon source. Soil nutrient decreases with vegetation degradation, so the protection of steppe vegetation from over grazing is very important.

Key words: soil organic carbon density (SOCD), soil total nitrogen density (TND), land use types, soil texture, plant degradation