基于GIS的水土保持措施下坡耕地土壤养分变异特征

Variation Characteristics of Soil Nutrients in Sloping Farmland With Measures of Soil and Water Conservation Based on GIS

以水保林地、水平梯田及地埂植物带组成的水土保持措施体系和无措施坡耕地土壤养分为研究对象,利用GPS定点采样,传统统计分析和ArcGIS地统计分析相结合,并通过参数及误差值对比,选取最佳空间插值拟合模型(球状模型),研究水土保持措施体系和无措施坡耕地土壤养分的空间变异特征。结果表明:(1)5个指标的空间变异度对比:TP>有效P>TN>有机质>pH,其TN,TP,有效P,pH值的空间变异受水土保持措施影响显著,有机质不仅受非人为因素影响,也受人为因素影响。(2)运用Kriging插值制图显示,5个指标在空间上分布均不均匀。采取水土保持措施后对土壤养分有一定的富集作用,含量显著高于无措施对照区;无措施坡耕地坡上、坡中和坡下部位土壤养分呈规律性降低趋势。而土壤pH值空间变异与有机质,TN,TP和有效P相反。(3)上坡位的水保林地对TN,TP和有机质的拦蓄作用最好,中坡位的水平梯田对有效P的拦蓄作用显著;由于下坡位的无措施对照区作为土壤养分流失的必经区域,土壤养分含量较高,表现出地埂植物带对养分的拦蓄作用不显著。通过土壤pH值的空间对比发现,种植相应植物使水保林地和地埂植物带土壤pH值下降了。

We selected soil nutrient in soil and water conservation measures system composed of water conservation forest,level terrace and terrace plants and no measures slope farmland as the research sample.We used GPS to locate the sampling point and combined traditional statistical analysis and ArcGIS′s statistical analysis,compared the parameters and error values,and selected the best spatial interpolation model（spherical model）to study soil nutrient spatial variability in soil and water conservation measures system and no measures slope farmland.The results showed as follows.（1）The spatial variability of five indicators follows the order：TP〉available P〉TN〉organic matter〉pH,the spatial variabilities of TN,TP,available P and pH are significantly affected by soil and water conservation measures,while organic matter is impacted not only by non-human factors but also by human factors.（2）The use of Kriging interpolation mapping shows that the five indicators unevenly distributed in the space.The content of soil nutrient resulting from taking conservation measures was significantly higher than that of the control area.From the top of the hill to the bottom of the slope,soil nutrient decreased regularity under no measure.The spatial variation of soil pH was opposite to that of organic matter,TN,TP and available P.（3）Soil and water conservation forest interception effects on TN,TP and organic matter are the best,and the interception effect of level terrace of P is significant.As a result of no control area as a necessary sink part of the lost soil nutrients,soil nutrient content was high in this area,showing that ridge plants have no significant effect on nutrient retention.Withregard to pH in space,the corresponding planting plants make soil pH value of in water conservation forest and ridge plant belt decrease.