Effects of DEM grid resolution on quantitative soil-landscape model at hilly and mountain area

Guo Pengtao , Wu Wei , Liu Hongbin , Xie Deti , Li Maofen 基于数字高程模型（Digital Elevation Model，DEM）的定量土壤-景观模型的精度依赖于DEM栅格分辨率，而DEM栅格分辨率如何影响土壤-景观模型及其预测精度目前研究较少。以西南丘陵山地区一典型汇水盆地为研究对象，以该区2.5、5、10、20和30 m DEM为基础，利用逐步线性回归方法建立起研究区不同分辨率下的定量土壤-景观模型，并应用这些模型预测研究区内土壤表层碱解氮含量的空间分布，进而比较DEM不同分辨率下土壤-景观模型及其预测精度。结果表明，随着DEM栅格分辨率的降低，比汇水面积、地形湿度指数的均值逐渐增加；平均坡度逐渐降低；曲率变化的范围逐渐减小。地形指数的这一变化规律对土壤-景观模型及其预测结果产生显著影响，模型的校正决定系数、平均绝对误差和均方根误差都以5 m栅格分辨率为转折点，分辨率低于5 m，模型的校正决定系数显著减小，平均绝对误差和均方根误差显著增加。 Abstract: The effect of digital elevation model (DEM) resolutions on soil-landscape model prediciton accuracy was evaluated by comparing five DEMs (2.5, 5, 10, 20, and 30 m) for a 4.8 km2 watershed in Chongqing. A set of soil-landscape models between soil property and terrain attributes were generated using mutiple stepwise regression. The results showed that the DEM grid resolution had significant effects on the terrain attributes. The mean of specific catchment area and topographic wetness index increased with the decrease of the grid resolution, while the mean of slope and the range of plan curvature and profile curvature decreased with the decrease of the grid resolution. The prediction accuracy of the soil-landscape models was subsequently influnced by the DEM resolutions. The determination coefficient significantly decreased while the mean absolute error and root mean square error remarkably increased when the grid size was lower than 5 m.