Effects of grazing on spatial distribution of shear strength in Inner Mongolia Grassland

To understand the change of soil shear strength and its’ spatial distribution, two sites: Continuous Grazing (CG) and Un-grazed since 1979 (UG79) were investigated by Hand-held vane tester. In each site, a regular sampling grid which covered an area of 105 m×135 m and included 100 points was positioned by GPS. The results showed that, CG induced the reduction of porosity and the increase in bulk density which resulted in the greater shear strength than UG79 within higher litter and soil organic matter. At both UG79 and CG sites, the obvious difference in spatial distribution of shear strength from dry soil water condition to moderate soil water condition indicated that soil water content, at some extent, determined the spatial distribution of shear strength. However, such capacity was limited when soil water content increased, which suggested that soil has the ability to maintain spatial distribution of shear strength itself.