Analysis of soil microbial dynamics at a cropland-grassland interface in an agro-pastoral zone in a temperate steppe in northern China

Grassland conversion is common around the world, and numerous studies have documented the effect of grassland conversion on biotic and abiotic soil conditions. Soil microbes are a key component of the underground ecosystem and are important in the circulation of materials and energy. In this study, we investigated the variations in the microbial community structures at a cropland-grassland interface. We used the transect line method and phospholipid fatty acid analysis in an agro-pastoral zone in northern China. The results show that significant differences occurred in the soil microbial community structures between grassland and cropland environments. These differences had significant seasonal variations. The variation pattern of soil microbial communities was very different from that of soil physical and chemical properties. Three main conclusions are presented: (1) Significant differences in soil properties, phospholipid fatty acid contents and microbial community structures occurred between the grassland and cropland environments after decades of reclamation. (2) At the grassland-cropland interface, we found a transition zone where the soil microbial community showed dramatic variations. (3) In the transition zone, soil microbial community structures were subjected to a stronger influence from farmland environments before sowing, but grassland played a major role after the crops were harvested.