侵蚀作用对黄土丘陵沟壑区有机碳迁移-沉积的影响

土壤有机碳(SOC)作为陆地碳库的重要组成部分,不仅对土壤肥力产生重要影响,而且在一定程度上影响着全球变暖趋势,为了深入探究土壤侵蚀与有机碳的关系,利用137 Cs核示踪法,以黄土丘陵沟壑区典型流域王茂沟坡耕地、林地、草地和梯田四种土地利用为研究对象,分析了不同坡面下土壤侵蚀对SOC迁移和沉积的影响规律。结果表明:与该流域137 Cs面积浓度背景值相比(1237 Bq/m²),坡耕地平均137 Cs面积浓度最小,平均137 Cs流失率最大,达到95.86%。根据侵蚀速率,四种坡面景观侵蚀速率大小依次为:坡耕地>草地>林地>梯田。根据土壤有机碳空间分布特征发现,除坡耕地外,林地、草地和梯田土壤沉积与土壤侵蚀同时发生,并且土壤137 Cs面积浓度与有机碳面积浓度呈现显著相关关系(p<0.05)。研究结果表明采用137 Cs核示踪法可以较为科学的解释该区域土壤侵蚀作用对坡面有机碳迁移-沉积的影响规律。

Effects of soil erosion on organic carbon migration and deposition of cultivated loessial soils in hilly-gullied loess region

With the change of land use pattern,the soil erosion state changed,which makes it difficult to determine the process of translocation and deposition redistribution of organic carbon.Therefore,in order to identify the speed of slope erosion and the changing law of the spatial distribution of organic carbon,Wangmaogou,as one of the typical regional basin of loess hills,was taken as the object.By using 137Cs tracer method,the samples of 137Cs soil from the soil depths from 0 to 5 cm and samples of topsoil were collected from different landscapes,including farmland,forest,grassland and terraces.By measuring 137Cs and organic carbon content of the soil,the influence of the soil erosion on the migration and the deposition of SOC under different land uses was analyzed.By measuring the area concentration and distribution state of 137Cs at different locations,soil erosion rates at different locations were estimated.The results show that the background value of 137Cs area concentration in this small watershed is 1237 Bq/m2.The average figure of 137Cs area concentration of sloop farmland is the smallest,while its average figure of 137Cs loss rate is the highest,reaching 95.86%.Four different landscapes were listed according to the figures of slope erosion rate in descending order:slope farmland>grassland>forest land>terrace.The concentration of organic carbon in slope farmland is the lowest;the concentration of organic carbon in woodland increases firstly and then gradually decreases from the top to the bottom of the slope.The concentration of organic carbon in grassland increases from the top to the bottom of the slope,and the concentration of organic carbon in terraces decreases from the top to the bottom of the slope.Moreover,there is a significant correlation between soil 137Cs area concentration and organic carbon area concentration(p<0.05).The results show that 137Cs nuclear tracer method can scientifically explain the influence of soil erosion on slope organic carbon translocation and deposition.