Response of Soil Micro-structure to Land Use Shifting in the Loess Plateau of China.
Xiubin He Sr., Inst of Mountain Hazards and Environment, No 9, Block 4, South Renmin Rd,, Chengdu, 610041, China and Guobin Liu, Inst of Soil and Water Conservation, 26 Xinong Rd, Yangling, 712100, China.
Soil structure is a base for its ecological functions and sensitive to environmental disturbance, especially in the areas where soil material is chemically homogeneous. Soil bulk samples and undisturbed samples were taken in farming land, different-year-old (3 years, 8 years and 20 years) grasslands restored from farmlands and permanent grassland in the loess hilly-gully region of the Loess Plateau, China. Analysis on soil texture, bulk density, organic matter, aggregate and thin section investigation had been carried out to understand the effects of land use shifting on soil micro-structure. The soil organic matter in the topsoil of farming land is 0.842% and 5.921% in permanent grassland; soil bulk density is 1.04 g.cm-3in farming land and 0.65 g.cm-3 in permanent grassland; and aggregate stabilities are 28.21% and 73.84%, respectively. Micromorphological features were dominated by small granular and subangular structures, voids of earthworms or roots, a number of micro-aggregates and abundant pore space in the samples from the permanent grassland. The thin sections from the farming land are characterized by very fine granular structure with groundmass of silasepic and abundant secondary calcium carbonate. Those imply that land use shifting had greatly influenced on the structure of the loessial soil and consequently its ecological function. And soil micro-structural indicators could be a sensitive proxy indicator for soil quality assessment in that region.