关键词: 封育, 水平沟, 鱼鳞坑, 土壤理化性质, 土壤质量, 典型草原

Abstract: Study of soil physico-chemical properties and their change over time under different grassland ecological restoration practices provides scientific data for use in regional planning. This research compared soil properties under traditionally grazed grassland (Control) and 3 restoration practices in place for 15 years on hill slopes: grazing exclusion by fencing, contour trenching, and short trenches placed in a fish scale pattern. Data on soil particle size, bulk density, fractal D value, water retention, porosity, organic matter, and nitrogen, phosphorous and potassium concentrations were evaluated using principal component analysis and a soil quality comprehensive index (SQI) defining recovery of soil quality under the different measures was constructed. The results indicated: 1) Soils on contour-trenched land had the highest content of clay particles, while the highest content of silt occurred in grazed grassland, and land with fish-scale pits had the highest sand content. The fractal dimension (D value) of soil particle volume ranked in order from highest to lowest contour trenches, grazing exclusion, fish-scale pits and grazed control. Vertical variation through the profile in soil particle size was weak. 2) The highest soil bulk density occurred on the grazed control land (1.14 g·cm^-3), followed by grazing exclusion, contour trenches and fish-scale pit land. Thus, the evaluated remediation practices significantly reduced the soil bulk density and increased soil total porosity and water holding capacity. However, the remediation practices had little effect on soil capillary porosity and non-capillary porosity. The vertical variation soil physical properties was not statistically significant. 3) The soil organic matter, total nitrogen and alkali-nitrogen showed a gradient: grazing exclusion>grazed control>fish-scale pits>contour trenches. The available potassium of soil in grazed control land was higher than with grazing exclusion, and fish-scale pits had the lowest available potassium among the 4 treatments. Soil nutrient concentrations were higher in the upper soil layers. 4) The comprehensive index of soil quality was: grazing exclusion (0.719)>contour trenching (0.348)>grazed control (0.337)>fish-scale pits (0.281). Based on this study of soil physical and chemical properties under the 3 restoration practices, it is concluded that grazing exclusion (fencing) provides the most significant improvement in soil quality and is the most appropriate ecological restoration measure for grassland in the study area.

Key words: enclosure, contour trenches, fish-scale pits, physical and chemical properties of soil, soil quality, typical steppe