Spatiotemporal variations of soil physical characteristics in rocky desertification areas of Guizhou karst-cluster depression

The karst peak cluster depression is ranked as the second place of eight rocky desertification control areas in our country, which is of 3.1 million hm2. Guizhou province is the region with most serious rocky desertification nationwide. In combination of field investigation with laboratory analysis and using SPSS19.0 statistics method, this work focused on the change of soil physical characteristics in different seasons and different landform parts of this region. The results show that，(1) There is big spatial and temporal differentiations. Besides a few loci with weak variation, others are characterized by medium degrees of variation related to complex and varied habitat types and heterogeneity of habitat height. (2) Soil physical characteristics do not change significantly with slopes, while showing prominent variations in different landforms (upper, middle and lower slopes) and different seasons (spring, summer, autumn, winter). (3) For different vegetation types, in addition to the non-capillary porosity, soil physical characteristics such as natural water content change significantly. In the areas with shrubbery and secondary woodland (economic fruit woods), the soil is relatively loose and the permeability is good, while in the coniferous forests or grassland areas, the soil is viscous and heavy, and the permeability is relatively poor.