科尔沁沙地土壤碳储量插值计算对比及其影响因素分析

Comparison of interpolation calculation of soil carbon storage and its influencing factors in Horqin Sandy Land

准确估算土壤碳储量对碳中和的实现与气候变化应对有着重要意义。本研究以地处我国北方半干旱农牧交错带东端的科尔沁沙地为研究区域,基于310个位点0-100 cm深土壤的有机碳数据,用不同插值方法[反距离权重法(IDW)、普通克里金法(OK)和回归克里金法(RK)]对土壤有机碳密度(SOCS)进行空间插值并计算区域土壤有机碳储量,使用平均误差(ME)、平均标准化误差(MSE)和均方根误差(RMSE)对插值结果进行评价,结合实测SOCS验证土壤碳储量计算的最优插值方法。结果表明:1)在半干旱沙地SOCS估算中,最终进入回归预测模型的环境变量按影响程度从大到小依次有年积温、降水量、砂土含量和海拔,SOCS与海拔、年积温、降水量和砂土含量存在显著负相关关系;2)不同插值方法计算的区域土壤有机碳储量具有显著差异(P<0.05),基于RK、IDW和OK计算得土壤有机碳储量分别为150.34、158.03和140.11 Tg。与实测值相比,OK低估了土壤有机碳储量,IDW高估了土壤有机碳储量,这种差异凸显了插值方法在区域尺度土壤有机碳储量估算中的重要性;3)基于RK插值的结果最优(ME=0.208,MSE=1.211,RMSE=1.973,R^(2)=0.3706),相比于OK和IDW的插值精度分别提高了6.0%和22.4%。本研究表明在半干旱沙地RK插值仍然适用并且可以提高插值精度,能更加准确地估算土壤有机碳储量。

Accurate estimation of soil carbon stocks is crucial to the realization of carbon neutrality and response to climate change.This study used different interpretation methods including inverse distance weighting(IDW),ordinary kriging(OK),and regression kriging(RK)to interpolate soil organic carbon stock and calculate regional soil organic carbon storage based on the organic carbon data of 310 sites in the 0-100 cm soil layer in Horqin Sandy Land,which is located in the eastern end of the semi-arid farming-pastoral ecotone in the north of our country.Mean error(ME),mean normalized error(MSE),and root-mean-square error(RMSE)were used to evaluate the interpolation results,and the optimal interpolation method for soil carbon storage calculation was verified with measured SOCS.The results showed that:1)in the estimation of SOCS in semiarid sandy land,the environmental variables that enter the regression prediction model are annual accumulated temperature,precipitation,sand content,and altitude in order of influence degree from large to small.SOCS showed significant negative correlation with altitude,annual accumulated temperature,precipitation,and sand content.2)the soil organic carbon stocks calculated by different interpolation methods were significantly different.The soil organic carbon stocks calculated by RK,IDW,and OK were 150.34,158.03,and 140.11 Tg,respectively.Compared with the measured values,OK and IDW underestimated and overestimated soil organic carbon stock,highlighting the importance of the interpolation method in the estimation of soil organic carbon stock at the regional scale.3)the results based on RK interpolation were optimal(ME=0.208,MSE=1.211,RMSE=1.973,R^(2)=0.3706)and improved the interpolation accuracy by 6.0%and 22.4%compared with OK and IDW,respectively.This study shows that RK interpolation in semi-arid sandy land can still improve the accuracy of interpolation,leading to more accurate estimation of soil organic carbon storage.