Structural Indicator Response of Soil Quality to Forestry Cultivation on the Loess Plateau of China

Soil quality is defined as capacity of a specific kind of soil to function within natural or managed ecosystem boundaries, to sustain biological productivity, maintain environmental quality, and promote plant and animal health. It is increasingly proposed as an integrative indicator of environmental quality, food security and economic viability. Soil structure is a base for its ecological function and sensitive to environmental disturbance, especially in the areas where soil material is chemically homogeneous. The present paper introduces a downscale method to evaluate soil structural quality of loess soil. Depth of topsoil, aggregate stability, organic matter, micromorphological characteristics and porosity, were investigated in loess soil in forestland and cultivated land, and statistically quantified by computer software. After 10 years cultivation, the 60cm-depth of topsoil had been completely depleted; soil porosity indicator had decreased by 69% and macro-pore space, by 26%. All the soil structural indicators imply the soil quality has greatly declined because the vegetation destroyed and the land cultivated. Soil erosion rate in the 10 year cultivated land was a thousand times of that in the forestland. It implies that soil structural indicators were a sensitive proxy indicator for soil quality in that region.