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土壤质量是支撑地球生物圈和进行可持续农业生产的最重要的环境因子之一。以黄土丘陵沟壑区的纸坊沟流域为研究区,选取不同植被类型和不同恢复年限的样地8块,测定土壤微生物性质(微生物生物量碳、微生物生物量氮、微生物生物量磷、微生物商)、土壤化学性质(土壤有机碳、全氮、碳氮比、碱解氮、销态氮、铵态氮和速效磷)、土壤酶活性(转化酶活性、碱性磷酸酶活性、脲酶)、土壤物理性质(黏粒、物理性黏粒、团聚体分形维数、团聚体平均质量直径、团聚体几何平均直径)等19个土壤属性。基于因子分析和隶属度函数,计算土壤质量指数(SQI),研究陕北黄土丘陵沟壑区植被类型对土壤质量的影响。结果表明:土壤质量指数(SQI)变化介于0.09～0.73之间,其中,农地土壤质量指数最小,SQI为0.09,31年刺槐地SQI最高,其值为0.73。同一植被类型下,SQI随植被恢复年限的增加而增加;相同恢复年限下,刺槐林地的SQI大于油松林。表明植被重建和农地撂荒会提高土壤质量,而粗放的农业耕作会降低土壤质量。
Soil quality is one of the most important environmental factors that support the Earth’s biosphere and carry out sustainable agricultural production. Taking the Zhifanggou watershed in the hilly and gully region of the Loess Plateau as the study area, 8 plots of different vegetation types and different restoration years were selected to measure the soil microbial properties (microbial biomass carbon, microbial biomass nitrogen, microbial biomass phosphorus, microbial biomass ), Soil chemical properties (soil organic carbon, total nitrogen, carbon to nitrogen ratio, available nitrogen, pin nitrogen, ammonium nitrogen and available phosphorus), soil enzyme activities (invertase activity, alkaline phosphatase activity, urease) Soil physical properties (clay, physical clay, fractal dimension of aggregates, aggregates average mass diameter, aggregates geometric mean diameter) and other 19 soil properties. Based on factor analysis and membership function, soil quality index (SQI) was calculated to study the effect of vegetation types on soil quality in loess hilly and gully regions of northern Shaanxi. The results showed that the soil quality index (SQI) ranged from 0.09 to 0.73, of which, the soil quality index of agricultural land was the smallest with SQI of 0.09, and the highest SQI of locust in 31 years was 0.73. Under the same vegetation type, SQI increased with the increase of vegetation restoration years. Under the same restoration years, the SQI of Robinia pseudoacacia forestland was higher than that of Pinus tabulaeformis forest. This suggests that revegetation and land abandonment will improve soil quality, while extensive agricultural practices will reduce soil quality.