1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 210008, Nanjing, China; 2. The Center of Soil and Water Conservation Monitoring, Ministry of Water Resources of the People's Republic of China, 100053, Beijing, China; 3. College of Ecology and Environment, Chengdu University of Technology, 610059, Chengdu, China; 4. University of Chinese Academy of Sciences, Nanjing, 211135, Nanjing, China
Abstract：[Background] Soil erodibility(named K factor) is one of the key parameters of the soil erosion equation. The K is the basic data for soil erosion monitoring, reflecting the difficulty of soil dispersion and transportation under the action of rainfall erosion, and its size is related to the characteristics of the soil. However, the existing national K map was made based on soil species data, and the survey was conducted nearly 40 years again. Besides, the soil-polygon linked method was used to produce the legacy map, which cannot reflect the K variability existing in the same soil polygon. [Methods]This article updated the national K-value map based on the soil series survey(completed from 2008 to 2018) and the random forest regression model. Firstly, the soil texture and organic matter content of 4 327 sample points were collected, and the K was calculated using the nomograph equation; when the soil organic matter content was >12%(mass fraction), the corrected EPIC formula was used to calculate the K. Secondly, the random forest regression model was used to train the K of the sample points, and a variety of environmental factors were used as prediction variables, including climate, surface temperature, vegetation index, terrain and parent rock type, and then remote sensing images were used to carry out spatial mapping. [Results]The cubic spline function combined with natural logarithm interpolated the content of very-fine sand content(≥0.050-0.100 mm) with high R2 and reasonable value. An exponential equation was built between the Nomo-K and EPIC-K values(R2=0.807 1). The updated map showed that the range of national K values was 0.005 1-0.074 5 t·hm2·h/(MJ·mm·hm2), with an average value of 0.029 8 t·hm2·h/(MJ·mm·hm2). The map of soil erodibility in China showed the macro rule that the K of the Loess Plateau and North China Plain was the largest, that of the southern and northeastern regions was the middle, and that of the Qinghai Tibet Plateau was the lowest. The spatial difference of the K factor was related to the distribution of main soil types in China. Besides, the divisions of soil and water conservation regions had various K values due to the comprehensive effect of natural factors and human activities. However, the updated K values still need to be corrected based on the measured data of runoff plots when applied in practice. [Conclusions]Our study improved the calculation method of the K, which is more accurate and objective. The updated K map reflects the recent soil condition and expresses the spatial variation of K in more detail with a 30 m resolution grid on a nationwide scale. This study will provide methods and data support for soil erosion investigation and monitoring.
OLSEN T G,WISCHMEIER W H.Soil-erodibility evaluations for soils on the runoff and erosion stations[J].Soil Science Society of America Journal,1963,72(5):590.
[2]
梁音,刘宪春,曹龙熹,等.中国水蚀区土壤可蚀性K值计算与宏观分布[J].中国水土保持,2013(10):35.LIANG Yin,LIU Xianchun,CAO Longxi,et al.K value calculation of soil erodibility of China water erosion areas and its macro-distribution[J].Soil and Water Conservation in China,2013(10):35.
[3]
WISCHMEIER W H.A soil erodibility nomograph for farmland and construction sites[J].Journal of Soil and Water Conservation,1971,26:189.
[4]
ADDIS H K,KLIK A.Predicting the spatial distribution of soil erodibility factor using USLE nomograph in an agricultural watershed,Ethiopia[J].International Soil and Water Conservation Research,2015,3(4):282.
[5]
PARYSOW P,WANG Guangxing,GERTNER G Z,et al.Assessing uncertainty of erodibility factor in national cooperative soil surveys:A case study at Fort Hood,Texas[J].Journal of Soil and Water Conservation,2001,56(3):207.
[6]
EFTHIMIOU N.The new assessment of soil erodibility in Greece[J].Soil and Tillage Research,2020,204:104720.
[7]
AVALOS F A P,SILVA M L N,BATISTA P V G,et al.Digital soil erodibility mapping by soilscape trending and kriging[J].Land Degradation & Development,2018,29(9):3021.
LIU Feng,ZHANG Ganlin,SONG Xiaodong,et al.High-resolution and three-dimensional mapping of soil texture of China[J].Geoderma,2019,361:114061.
[10]
张甘霖.中国土系志[M].北京:科学出版社,2020:1.ZHANG Ganlin.Soil series of China[M].Beijing:Science Press,2020:1.
[11]
张甘霖,王秋兵,张凤荣,等.中国土壤系统分类土族和土系划分标准[J].土壤学报,2013,50(4):826.ZHANG Ganlin,WANG Qiubing,ZHANG Fengrong,et al.Criteria for establishment of soil family and soil series in Chinese soil taxonomy[J].Acta Pedologica Sinica,2013,50(4):826.
[12]
鲍士旦.土壤农化分析[M].3版.北京:中国农业出版社,2008:1.BAO Shidan.Agrochemical analysis of soil[M].3rd edition.Beijing:China Agriculture Press,2008:1.
[13]
TIAN Zhiyuan,LIU Feng,LIANG Yin,et al.Mapping soil erodibility in southeast China at 250 m resolution:Using environmental variables and random forest regression with limited samples[J].International Soil and Water Conservation Research,2022,10:62.
[14]
周洋,赵小敏,郭熙.基于多源辅助变量和随机森林模型的表层土壤全氮分布预测[J].土壤学报,2022,59(2):451.ZHOU Yang,ZHAO Xiaomin,GUO Xi.Prediction of total nitrogen distribution in surface soil based on multi-source auxiliary variables and random forest approach[J].Acta Pedologica Sinica,2022,59(2):451.
[15]
杨欣,郭乾坤,王爱娟,等.基于小区实测数据的不同类型土壤可蚀性因子计算[J].水土保持通报,2019,39(4):114.YANG Xin,GUO Qiankun,WANG Aijuan,et al.Calculation of soil erodibility factor under different soil types based on runoff plot data[J].Bulletin of Soil and Water Conservation,2019,39(4):114.
[16]
冯克义.我国土壤可蚀性值K值研究[J].水利水电技术,2019,50(S2):225.FENG Keyi.Study on K value of soil erodibility in China[J].Water Resources and Hydropower Engineering,2019,50(S2):225.
[17]
刘斌涛,陶和平,史展,等.青藏高原土壤可蚀性K值的空间分布特征[J].水土保持通报,2014,34(4):11.LIU Bintao,TAO Heping,SHI Zhan,et al.Spatial distribution characteristics of soil erodibility K value in Qinghai-Tibet Plateau[J].Bulletin of Soil and Water Conservation,2014,34(4):11.
[18]
张科利,蔡永明,刘宝元,等.黄土高原地区土壤可蚀性及其应用研究[J].生态学报,2001,21(10):1687.ZHANG Keli,CAI Yongming,LIU Baoyuan,et al.Evaluation of soil erodibility on the Loess Plateau[J].Acta Ecologica Sinica,2001,21(10):1687.
[19]
张科利,彭文英,杨红丽.中国土壤可蚀性值及其估算[J].土壤学报,2007,44(1):8.ZHANG Keli,PENG Wenying,YANG Hongli.Soil erodibility and its estimation for agricultural soil in China[J].Acta Pedologica Sinica,2007,44(1):8.
[20]
徐祥明,高珍萍,邱秀亮,等.赣南不同母质及植被覆盖对红壤水稳性的影响[J].水土保持通报,2015,35(5):55.XU Xiangming,GAO Zhenping,QIU Xiuliang,et al.Effects of different parent material and vegetation coverage on water stability index of red soils in Gannan area[J].Bulletin of Soil and Water Conservation,2015,35(5):55.
[21]
WANG Bin,ZHENG Fenli,RÖMKENS M J M.Comparison of soil erodibility factors in USLE,RUSLE2,EPIC and Dg models based on a Chinese soil erodibility database[J].Acta Agriculturae Scandinavica,Section B:Soil & Plant Science,2013,63(1):69.
2023, Vol. 21 
