小流域土壤氮磷空间变异特征分析

应用经典统计学与地统计学相结合的方法,以长江下游地区岔河小流域为研究区域,分析了不同土地利用方式下土壤中氮磷含量在0~15 cm和15~30 cm两种深度中的空间分布特征。结果表明:流域内旱地、水田及撂荒地中氮磷含量分布特征差别很大,变异系数迥异;氮和磷的空间分布均为各向异性,长轴方向多为东北-西南;对于0~15 cm土壤层,长轴变程在750~950 m之间,变程从大到小依次为全磷、铵态氮、全氮、有效磷、硝态氮;小流域全氮高含量值主要集中在流域南部水田较为集中的地方,含量梯度与坡面径流方向一致;而全磷受农业耕作及土壤颗粒迁移的双重影响,在小流域南部及北部旱作区聚集的地方分别出现高值区;全氮、全磷在3种耕作方式下呈现出相似的结构性,且水田中正相关尺度均大于旱地,空间正相关尺度与变异系数表现出很好的一致性。

Spatial Variability of Soil Nitrogen and Phosphorus in Small Watershed

Geo-statistics combined with classical statistics were applied to analyze the spatial distribution of soil nitrogen (N) and phosphorus (P) content under three different land uses in Chahe watershed at the lower Yangtze River. The results showed that soil N and P content distribution varied significantly in paddy, upland, and vacant land, while the coefficient of variation also varied greatly among the three land uses. All spatial distributions of N and P content values were anisotropic and directions of most long axes were northwest-southeast. Major ranges in topsoil were between 750~950m with the order of total P(TP)>ammonia N (AN)>total N (TN)>available P (AP)>nitrate N (NN). Higher content of TN was mainly concentrated in the southern part of the small watershed and the gradient direction was consistent with the direction of surface runoff, while distribution of TP was significantly affected by farming and soil particle movement, and the high level of TP was appeared in the accumulation area of the south of small watershed and the north of arid region. TN and TP showed similar structural characteristics under the three farmland types, while both the autocorrelation scales in paddy land were larger than those in upland. Variation of spatial autocorrelation scales showed good consistency with the coefficient of variation. Research results provided a scientific basis for the control of N and P losses in agricultural production and the establishment of non point source pollution model.