Abstract: The study used field investigation and chemical analysis to explore soil nutrient contents under grassland,woodland and cultivated land in the farming-pastoral ecotone in Siziwang banner,Inner Mongolia.Principal component analysis was used to evaluate the soil nutrient contents,and the results were compared with soil nutrient contents determined in the Second Soil Survey in 1982.Average of soil organic matter content in grassland and woodland was 21.22 g/kg and 23.14 g/kg,respectively,which was significantly higher than that of cultivated land.Furthermore,the average values of total nitrogen,available nitrogen and available potassium were also higher than for cultivated land.Overall,the soil nutrient content level of cultivated land was lower than that of grassland and woodland.Principal component analysis showed that soil nutrients under the different land use types followed a ranking of woodland>grassland>cultivated land.Compared with 1982,the organic matter content of grassland and cultivated land had increased by 104.0% and 21.6% respectively in 2017.Thus,although soil nutrient content was restored under each type of land use,the degree of restoration in grassland was better than that of cultivated land.According to the above results,increasing the protection of woodland and grassland,and the management of cultivated land are better choices for maintaining the soil sustainable development in the Farming-pastoral ecotone which in Siziwang banner,Inner Mongolia.

Key words: Farming-pastoral ecotone;Land use;Soil nutrient content