Effects of land use type on soil nutrients in the semiarid area of western Jilin Province——A case study in Tongyu County of Jilin

Taking Tongyu County as a typical study area,this paper evaluated the effects of land use type and its changes on soil nutrients in the surface soil of semiarid area of western Jilin Province.Field soil sample data and land use data were used to identify land use changes within two typical periods of 1986 and 2006,to examine soil nutrient changes between 1986 and 2006,and to analyze the relationship between land use changes and soil nutrient changes.The results indicated that the spatial pattern of land use types in Tongyu County had obvious changes in recent 20 years.The area percentage of cropland increased by 53%,while that of grassland declined from 27.3% to 13.5%.The level of soil nutrients in the surface soil of Tongyu County is very low.Total nitrogen,total phosphorus and total potassium of 2006 decreased significantly in comparison with 1986,while soil organic matter and available nutrients had no significant difference between 1986 and 2006.Among samples of 2006,significant differences between cropland,grassland and woodland were found on soil nutrients including total phosphorus and available potassium.Except total phosphorus,total potassium and available potassium,the contents of other soil nutrients in salina land were obviously lower than those in cropland,grassland and woodland.Land use changes had resulted in soil nutrient changes in the study area.Land reclamation led to the increase of soil organic matter,but other land use conversion resulted in the decrease of soil organic matter.Most total nutrients declined,while available nutrients increased after the conversion of land use type.