几种土壤属性制图方法的稳定性与影响因素分析

 本文以土壤CEC和土壤全氮为研究对象,在河南省黄河以北6个地市选取870个样点,并随机均分为两个数据集,进行了制图对比分析;同时研究了Kriging法、IDW法和以点代面法制图结果的稳定性及其与精度的关系,以及影响因素。结果表明:采用实测数据与预测数据的交叉验证并不能用来衡量制图结果的稳定性,验证精度高低并不表示采用不同数据集制图结果可能会重现的概率;而且采用不同的方式进行精度检验,结论也会有所不同。采用不同抽样集合制图,Kriging法和IDW的结果较稳定,两者较接近,其相对误差>0.3的区域均不超过20%,且相对差异度高值区的空间分布格局相对分散;而以点代面法制图结果不稳定,相对误差>0.3的区域达到54.21%,且差异度较高的图斑相对集中,呈大片状分布。制图结果稳定性受到实测数据分布特征和局部地区土壤的高度变异性的影响,其中Kriging方法制图结果的不稳定性受样点分布格局的影响较另两种方法要大,而IDW法和以点代面法受实测数据自身变异性影响更明显。

Analysis and Comparison in Stabilities and Related Influence Factors for Several Common Methods Used in Soil Property Mapping

Total 870 soil samples were collected from the north of Henan Province over a 27 955 km2 area.Two subgroups with 435 samples were respectively used in soil property map-making,i.e.the content of exchangeable cations（CEC） and the total nitrogen（TN）.The difference of map-making results between two subgroups was calculated.The stability among Kriging method,inverse distance weight method（IDW） and polygon value represented by point value method（PRP） were compared and its＇ influencing factors were discussed.The results showed that：（i） RMSE（Root Mean Square Error）and R（correlation coefficient） between measured data and predicted data could not represent the stability of map-making,namely,the returning probability of the spatial pattern of soil properties.And the result was differential in precision validation when using different ways.（ii） The stability of Kriging and IDW were significantly superior to the PRP.The area with relative difference lower than 0.3 didn＇t achieved 20% of the total area in Kriging and IDW mapping methods,but it achieved 51.57% in PRP mapping method.The area with a high difference level was scattered in the difference map when using the former two methods,but it was centralized and showed by big polygons when using PRP.（iii） The stability of soil property map-making results was disturbed by both sample distribution and high variability of soils in local area.Sample distribution was much important in keeping stability in Kriging method than that in IDW and PRP methods.In the two latter ways high variability among data values showed much impressive effects.