黄土高原水蚀风蚀交错带小流域土壤矿质氮空间变异性

为探明小流域土壤养分特性空间变异规律及其与环境因子的关系，以非均匀取样方法测定了黄土高原水蚀风蚀交错带小流域土壤表层（0～10、10～20、20～40 cm）的硝态氮和铵态氮，采用经典统计和地统计学方法分析了其空间分布特征及变异结构。结果表明：土地利用空间配置成混合利用结构拦截和减少径流侵蚀，形成了土壤矿质氮坡面斑块镶嵌格局。小流域内硝态氮和铵态氮呈中等的空间变异和自相关性，其变异性由土壤系统内部因素包括土壤质地、矿物、成土过程、地形特征和人类活动造成的外部因素包括施肥和耕作等共同控制。建立了土壤矿质氮多元回归预测模型，各回归模型的自变量不同，表明不同土层硝态氮和铵态氮的变异受不同环境因子控制。分析认为合理配置土地利用形成斑块状结构和增加养分投入可以改善研究区土壤质量。

Spatial variability of soil mineral nitrogen in a small catchment in the wind-water erosion crisscross zone of Loess Plateau

Objective of this study was to understand the spatial pattern of soil nutrient properties and their relationships with environmental factors in a small catchment. Spatial pattern and variability of surface (0-10, 10-20, 20-40 cm) soil ammonium and nitrate in a small catchment were analyzed combining with classical statistical and geo-statistics with data measured by non-uniform sampling method in the wind-water erosion of the Loess Plateau. Results showed that mixed land uses patterns developed by the spatial arrangement of different land uses could trap the runoff and sediments, which ultimately formed the plaque mosaic patterns of soil mineral nitrogen on the slope. Soil ammonium and nitrate presented moderate variability, and had moderate spatial autocorrelation. The spatial variability could be controlled by intrinsic variations in soil characteristics (texture, mineralogy, soil genesis processes and terrain) and extrinsic variations (soil fertilization and cultivation practices). The study built the spatial multiple regression-prediction models of soil mineral nitrogen under different soil layers. There were different variables entered to these models, which meant that at different soil depths, there were different environmental factors controlled the spatial variability of soil ammonium and nitrate. The results suggested that creating a mosaic pattern by land use arrangement and more nutrient matter input would improve the soil quality effectively on the hilly area of the Plateau.