Dynamics of soil microbial biomass carbon under different land-use in an ecotone in inner Mongolia Mountains of north China

The diversity of land use and incidence of wind erosion are common characteristics in inner Mongolia Mountains of north China. It is known that land use changes soil physical, chemical and biological properties. The objective of this study was to investigate the effects of land use on soil microbial biomass carbon (SMBC). Fumigation extraction method was used for measuring SMBC. Three land use types (forest land, grass land and farmland) and three depths of soil profile (0 - 10, 10 - 20 and 20 - 30 cm) were selected to monitor SMBC. The SMBC measurements were performed biweekly in farmland planted with spring oats from June to August 2005. The results showed that the mean SMBC of the 30 cm soil layer was highest in forest land with 493.8 mg kg(-1), which was 2.5 times that of grassland and 5.5 times that of farm-land. The SMBC of farmland under no-tillage (NT) increased with the fixed number of year practicing no-tillage. In forest land and grassland, the SMBC decreased with the soil depth. In farmland under no-tillage, the SMBC was highest in the 0-10 cm layer and lowest in of the 10-20 cm layer. However, the SMBC in farmland under plough tillage (PT) was adversely affected. Seasonal variations in SMBC concentrations were found in the farmland plot during plant growth periods. Our study suggested that land reclamation should be confined in appropriate scale and use of NT could protect the soil from biological degradation and maintain soil quality as compared with PT management.