地貌和样点数对耕地土壤有机质插值精度的影响

Effect of geomorphologic landscape and sampling numbers on the interpolation precision of cultivated land topsoil organic matter

将湖南省划分为洞庭湖平原区,湘东、湘中丘陵、中低山区,湘南丘陵、中低山区和湘西北中低山区四个地貌景观区,以高密度的耕地表层土壤有机质数据为基础,分析地貌和样点数对插值精度的影响。研究表明:湖南省耕地表层土壤有机质平均含量从高到低依次为:湘南丘陵、中低山区>湘东、湘中丘陵、中低山区>湘西北中低山区>洞庭湖平原区。湖南省耕地表层土壤有机质变异系数在31.23%~37.55%之间,属于中等变异水平;基底效应在12.3%~50.0%之间,其中湘东、湘中丘陵、中低山区和湘南丘陵、中低山区耕地表层土壤有机质呈现强烈的空间自相关,洞庭湖平原区和湘西北中低山区具有中等空间自相关。相同采样密度下,湖南省耕地表层土壤有机质的克里格插值精度从高到低依次为:洞庭湖平原区>湘西北中低山区>湘东、湘中丘陵、中低山区>湘南丘陵空间自相关、中低山区。四个区的耕地表层土壤有机质NRMSE均随着样点数的增加呈现出递减的趋势,表明插值精度逐渐提升。

The territory of Hunan Pro vince was divided into four areas to analyze the effects of geomorphologic landscape and sampling number on the Kriging interpolation precision of cultivated land topsoil organic matter which is Dongting Lake Plain, the hilly and middle-low mountainous area of eastern and middle Hunan, the hilly and middle-low mountainous area of southern Hunan and the middle-low mountainous area of northwestern Hunan. The results show that: the average of cultivated land topsoil organic matter in Hunan Province went down as follow: the hilly and middle-low mountainous area of southern Hunan > the hilly and middle-low mountainous area of eastern and middle Hunan > the middle-low mountainous area of northwestern Hunan > Dongting Lake Plain. The coefficient of variation of topsoil organic matter is between 31.23% to 37.55% which belongs to a moderate level of variability.The semi-variance nugget/sill ratio value of topsoil organic matter ranged from 12.3 % to 50.0%. The hilly and middle-low mountainous area of eastern and middle Hunan and the hilly and middle-low mountainous area of southern Hunan of topsoil organic matter showed the strong spatial correlation, the others showed the moderate spatial correlation. Under the conditions of the same sample density, the Kriging accuracy of cultivated land topsoil organic matter went down as follow: Dongting Lake Plain > the middle-low mountainous area of northwestern Hunan > the hilly and middle-low mountainous area of eastern and middle Hunan > the hilly and middle-low mountainous area of southern Hunan. The NRMSE of topsoil organic matter in four areas decreased with the increasing of sampling numbers, indicating that the interpolation accuracy gradually increased.