黄土高原不同地貌区土壤有机碳空间变异与合理取样数研究

论文运用经典统计学和地统计学相结合的方法,以黄土高原典型地貌丘陵沟壑区(庄浪县)与平原区(武功县)为例,探讨了土壤有机碳空间变异特征及县域尺度土壤有机碳的合理采样数。研究表明,丘陵沟壑区有机碳的变异系数较小,变化范围在0.176 到0.200 之间,平原区较沟壑区大,变化范围在0.24 到0.26 之间,基于经典统计学,在5%的精度要求和95%的置信区间,沟壑区的合理样本数为64 个,平原区为110 个。丘陵沟壑区与平原区两区域都呈现出强烈的空间相关性且变程较小,分别为2 250、900 m,庄浪县土壤有机碳含量高值区斑块较破碎,东部较西部多、北部比南部多;武功县土壤有机碳含量西南与中部地区含量较高,高值区比庄浪县相对集中。根据土壤有机碳的空间相关性和克里格插值的独立验证得出庄浪县与武功县的合理采样数分别为903、1 838 个,合理样本数的确定对合理评价黄土高原地区碳储量的预测精度有重要意义。

Spatial Variation and Reasonable Sampling Number of Soil Organic Carbon Under Different Geomorphic Types on the Loess Plateau

Geostatistics combined with classic statistics was applied to analyze the spatial variability and reasonable sampling number of soil organic carbon at county scale in the gully and plain regions of the Loess Plateau. The results showed that: 1) The coefficient of variation was relatively small in the gully region, ranging from 0.176 to 0.200. The plain presented a larger coefficient of variation, ranging from 0.24 to 0.26. 2) Classic statistical analyses showed reasonable sampling number was 64 in the gully region and 110 in the plain region by the 5% accuracy and 95% confidence interval. 3) The two regions both presented strong spatial dependence and small range, being 2250 m and 900 m respectively. In Zhuanglang County, the SOC contents in the north were higher than those in the south, the SOC contents in the west were higher than those in the east part, and some high values were in patch forms. In Wugong County, the SOC contents in the southwestern and central parts were high, and the high values were more concentrative. Based on the spatial correlation of SOC and validation,we concluded that reasonable sampling number of SOC was about 903 and 1838 in the gully and plain region respectively. The study was important to reasonably evaluate the prediction accuracy about soil organic carbon storage in the Loess Plateau region.