红壤区土壤有机质和全氮含量的空间预测方法

Spatial prediction of soil organic matter and total nitrogen in the hilly red soil region,China

如何利用有限的土壤采样点准确预测土壤属性一直是研究的热点。近些年来,结合辅助信息的克里格空间插值应用广泛,但将土地利用类型信息作为辅助变量提高预测精度的研究鲜有报道。以中国南方红壤丘陵区的余江县为案例区,用网格法采集254个土壤样品,通过普通克里格(OK)和以土地利用方式为辅助变量的克里格(KLU)方法对土壤有机质(SOM)和土壤全氮(STN)进行空间预测,并通过102个验证点比较了两种方法的预测精度。分析表明KLU对SOM和STN的预测值与实测值的相关系数(rSOM=0.786,rSTN=0.803)明显高于OK(rSOM′=0.224,rSTN′=0.307);OK对SOM和STN的预测RMSE分别为12.48g.kg-1和0.64g.kg-1,而KLU的预测RMSE分别为6.86g.kg-1和0.37g.kg-1,仅为前者的55%和58%。可见,KLU对研究区SOM和STN的预测精度均大幅提高。同时分析也表明,KLU对不同土地利用方式SOM和STN预测精度的提高幅度存在差异,其中对旱地预测精度的提高幅度最大,对林地预测精度的提高幅度最小,水田则介于两者之间。研究表明,KLU是南方红壤丘陵区进行SOM和STN空间预测的现实和高效方法。

There has been a great concern about how to accurately predict soil properties using the limited soil samples.At present,the approaches of Kriging interpolation coupled with auxiliary variables has been widely used.However,little information on improving prediction accuracy of soil organic matter（SOM）and total nitrogen（STN）with the aid of land use patterns as auxiliary variables is available.In this study,254 soil samples were collected in Yujiang County of the hilly red soil region,China,two approaches：ordinary kriging（OK）and kriging combined with land use patterns information（KLU）were used to predict SOM and STN spatial distribution pattern,and 102 samples were validated to compare the prediction accuracy of these two approaches.The results showed that the correlation coefficients between measured and predicted SOM and STN values using KLU approach（rSOM=0.786,rSTN=0.803）were both great larger than those using OK approach（rSOM＇=0.224,rSTN＇=0.307）.As for 102 validated samples,the root mean square error（RMSE）of SOM and STN using OK approach were 12.48 g·kg-1 and 0.64 g·kg-1,while those using KLU approach were 6.86 g·kg-1 and 0.37 g·kg-1,which were 55% and 58% of the former only.In terms of KLU approach,RMSE of drylands has the widest lowering range,and that of forestlands has the smallest lowering range.It is indicated that KLU approach is an efficient and practical prediction approach in the hilly red soil region,China.