北京市平谷区土壤有机质和全氮的空间变异分析

探明土壤有机质和全氮的空间分布，是合理科学配方施肥的重要依据。在北京市平谷区布设了1076个采样点，测定了其耕层（0～20cm）、亚耕层（20～40cm）土壤有机质和全氮的含量。统计结果表明，两个土层的有机质和全氮含量属中上水平，变异系数为中等程度变异，其剖面分布表现一定的表聚性；通过结构分析，耕层有机质和亚耕层全氮的理论模型采用球型模型拟合较好，耕层全氮及亚耕层有机质采用指数模型拟合较好，耕层土壤有机质与全氮的空间自相关范围较小，变程分别为18．32和19．0km，亚耕层有机质和全氮的变程较大，分别为131．9和51．0km，它们的空间变异主要是由结构性因素引起的；采用Kriging方法对未测点进行了估值，绘制了等值线图，表明有机质和全氮含量空间分布格局基本一致，由东北向西南逐渐减少，主要受地形、土壤类型、土地利用方式和施肥状况等因素的影响。

Spatial Variance of Soil Organic Matter and Total Nitrogen in Pinggu of Beijing

1 076 soil samples were collected from Pinggu county of Beijing and analyzed for concentrations of soil organic matter(SOM) and total nitrogen(TN) in topsoil(0～20 cm) and subsoil(20～40 cm)respectively.The statistical results indicate that the mean values of SOM and TN are higher level in two soil layers and their coefficients of variation belonged to the middle degree.The contents of SOM and TN topsoil are higher than in subsoil.The result of semivariance analysis show that topsoil SOM and subsoil TN fitted for spherical model,and topsoil TN and subsoil SOM are described by exponential model.In topsoil,SOM and TN content have the smaller spatial correlation distance,which are 18.32 and 19.0 km,respectively.However,the SOM and TN content in subsoil have a large spatial correlation distance,which are 131.9 and 51.0 km,respectively.The spatial variance is mainly induced by structural factors.The Kriging method is applied to calculate the unobserved points and is used to generate the contour map.SOM and TN contents show the same distributed patterns,which decline from east-north to west-south.And their spatial distribution is affected by topology,soil type,fertilization and land use types.