The subsurface flow constitutes an important portion of total runoff in the sloping field of red soil.However,the occurrence mechanism and quantification of subsurface flow are the difficult issues in red soil region.To determine the subsurface flow associated with different surface cover types on sloping red soil under natural rainfall events,observational data on surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012 in an experiment with three treatments (grass cover,litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park.The results show that land cover involving grass or residue can convert more of the surface flow into subsurface flow,and relieve the impact of seasonal rainfall on the surface flow generation in red region.Under individual rainfall event,the surface flow coefficients of grass cover and litter cover are 10.80％ and 12.55％ of that of bare land,while the subsurface flows are 2.47 times and 3.22 times of bare land.The generation characteristics of subsurface flow are significantly influenced by surface covers.The average annual subsurface flow coefficient at a depth of 30 cm is 79.25 percent of that at a depth of 60 cm for bare land.In contrast,subsurface flow generated in plots with grass or litter cover at a depth of 30 cm is greater in spring,taking 34.90％ and 39.63％ of the total annual output,respectively,without significant effect on subsurface flow at a depth of 60 cm.The process of subsurface flow is mainly affected by rainfall depth and duration except for the rainfall intensity.Therefore,surface cover could effectively regulate the rainfall-runoff relationship and control rainfall erosion in red soil sloping erosion control.The findings will be of significant interest to understand the mechanism of soil erosion and its conservation of red soil slope.%壤中流是红壤坡地降雨产流的重要组成,但其发生机理与定量化一直是研究的难点.本文通过野外大型水分渗漏小区长期定位观测,研究自然降雨条件下,不同下垫面(百喜草植草覆盖、百喜草干草敷盖与地表裸露)红壤坡地壤中流产流特征及其关键影响因素.结果表明:(1)植草覆盖和干草敷盖能有效减弱红壤区降雨季节性差异对地表径流的影响,降低地表径流,促进壤中流发育;(2)植草覆盖与干草敷盖的次降雨地表径流系数是地表裸露的10.80％和12.55％,而壤中流次降雨径流系数为地表裸露的2.47倍和3.22倍;(3)下垫面条件能显著影响壤中流的输出特征,地表裸露壤中流主要发生在60 cm层,次降雨径流系数是30 cm层的1.29倍,植草覆盖和干草敷盖主要影响30 cm层,对60 cm层影响较小,且30 cm层次降雨径流系数是60 cm层的1.44倍和2.22倍;(4)春季是植草覆盖与干草敷盖30 cm层壤中流的主要输出季节,输出量占全年的34.90％和39.63％,随着土层深度增加,60 cm层壤中流季节性差异降低;(5)壤中流受降雨量和降雨历时两个因子影响显著,与降雨强度无显著关系.在红壤坡地侵蚀治理过程中,科学的坡面覆盖类型能有效调节坡面降雨-径流特征,控制降雨侵蚀,该研究有助于进一步认识红壤坡地土壤侵蚀机制及防治.
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