3.1 Effects of grassland conversion on soil physicochemical properties
Grassland cultivation significantly decreased SOC, STN, soil moisture and pH, but did not change the C:N ratio (Figure 1, Table S1). We also observed significant decreases in SOC, STN and STP concentrations at increasing soil depths in grassland across all three sites (Table S1). However, the SOC, STN and STP concentrations in cropland did not differ significantly among different soil layers (Table S1). Moreover, we found significant decreases in >1mm soil aggregation and increases in <1mm soil aggregations (Figure S2) in the cropland sites compared with the reference grasslands. Furthermore, grassland conversion to cropland significantly declined the soil NH4+-N concentration, but increased the NO3--N concentration (Figure S3).