Effects of Soil Quality Arising from the Conversion of Intrazonal Grassland in an Agro-Pasturage Ecotone of China

Abstract

Understanding the effects of land-use changes on soil property is crucial for the sustainable development in an agro-pastoral ecotone of China. Although grassland conversion is an important land-use change in northern China, most studies have focused on zonal grassland areas and the intrazonal grassland areas have been ignored, which is not climatic climax of natural grassland, because it is constrained by terrain, surface water, components of the earth surface and other ecological factors. The present study aims to determine the effects of the conversion of intrazonal grassland into cropland on soil properties in the Bashang area where a typical agro-pastoral ecotone of northern China is found. The results showed that intrazonal grassland conversion and subsequent tillage practices increased soil bulk density and decreased soil porosity, capillary moisture capacity, and soil nutrients content. Available soil zinc content in the study area was at extremely low level, which could not meet the need of crop growing based on the soil trace elements appraisal criteria of China. On the average, the conversion of intrazonal grassland into cropland led soil organic carbon density (SOCD) decreased from 22.49 kg m-2 to 13.24 kg m-2, and soil total nitrogen density (STND) from 2.23 kg m-2 to 1.27 kg m-2; that is, the meadow conversion resulted in a 41-43% reduction of SOCD and STND in 0–60 cm soil depth over about 20 years. To conserve the present status, the further conversion of grassland into cropland should be stopped, and encourage the restoration of cropped area into grassland to combat the soil desertification and degradation in the agro-pasturage ecotone of Northern China.