Digital soil mapping and its implications in the extrapolation of soil-landscape relationships in detailed scale

Abstract: The objective of this work was to test the extrapolation of soil-landscape relationships in a reference area (RA) to a topographic map (scale 1:50,000), using digital soil mapping (DSM), and to compare these results to those obtained in similar studies previously conducted in Brazil. A soil survey in a 10 km2 RA, using conventional mapping techniques (scale 1:10,000), was made in order to map a 678 km2 physiographically similar area (scale 1:50,000) using DSM. The decision tree technique was employed to build a predictive extrapolation model based on soil classes and eight terrain attributes in the RA. The validation of DSM by application of field observation points resulted in a 66.1% global accuracy and in 0.36 kappa index. The most representative soils in the area were correctly predicted, whereas the less representative and less frequent soils in the landscape (and consequently with reduced sampling) had their prediction compromised. The RA proportion, which equals 1.5% of the total area, is a limiting factor in the formulation of soil-landscape relationships to precisely represent the mapped area by DSM.

摘要：本研究旨在借助数字土壤制图（Digital Soil Mapping，DSM）方法，将参考区域（Reference Area，RA）内的土壤-景观关系外推至比例尺为1:50000的地形图，并将该结果与巴西此前同类研究的成果进行对比。为利用DSM方法对678 km²、地貌特征相似的待制图区域（比例尺1:50000）开展土壤成图工作，研究团队先采用传统制图技术（比例尺1:10000）在10 km²的参考区域内完成了土壤调查。本研究采用决策树技术，基于参考区域内的土壤类型与8种地形属性构建了预测外推模型。通过野外观测点对数字土壤制图结果进行验证，结果显示整体准确率达66.1%，Kappa系数为0.36。区域内代表性较强的土壤得到了准确预测，而景观中代表性弱、发生频率较低且相应采样量不足的土壤，其预测精度受到了负面影响。参考区域仅占总面积的1.5%，这一比例限制了土壤-景观关系的构建精度，使其难以通过DSM方法精准表征待制图区域。