Soil macro-faunal communities along a cultivitated cropland chronosequence in semiarid agro-pastoral ecosystems, northern China

The semiarid agro-pastoral zone in northern China represents a typical degraded ecosystem under intensified human activities. This region has undergone profound land use changes during the past century, and natural grasslands have been progressively cultivated. However, the changes of soil macro-faunal community along a cultivated cropland chronosequence are largely unknown in this region. An investigation on soil properties and macro-fauna was carried out in 3, 10 and 20 years of tillage croplands, with an adjacent exclosure grassland as reference sites in Horqin Sand Land, northern China. Environmental parameters (soil bulk density, moisture, temperature, pH, electrical conductivity, organic carbon and total nitrogen) indicated a significant, negative effect of cultivation on soil conditions of exclosure grassland. Soil bulk density, temperature, pH, and electrical conductivity increased significantly, while soil moisture, organic carbon and total nitrogen decreased significantly after cultivation of grassland. There was considerable improvement of soil properties after 20 years of tillage, particularly in soil moisture, temperature and soil organic carbon and total nitrogen. Cultivation of grassland significantly decreased the density and richness, and them of functional groups, together with diversity index of soil macro-faunal community. But they increased progressively after 20 years of cultivation, though still significantly lower than that in the exlclosure grassland. Further, data for the different soil macro-faunal groups characterized specific responses and adaptation to varying soil conditions of croplands under tillage management with age. Soil moisture, pH and soil organic carbon and total nitrogen had the greatest influence on the faunal community structure. In conclusion, cultivation of exclosure grassland degraded the soil properties and soil macro-faunal diversity. Long-term (20 years) of tillage management could facilitate the recovery of soil properties, and also soil macro-faunal assemblies to some extent.