干热河谷冲沟发育区土壤细沟可蚀性及主要影响因素

为探明我国干热河谷区不同活跃程度冲沟不同空间部位土壤细沟可蚀性(Kr值)在不同近地表水文条件下的差异,在云南省元谋县选择不同活跃程度的冲沟,采集其不同空间部位(集水区、沟壁、沟床)的土壤样品,利用“V”形细沟模拟冲刷装置进行放水冲刷试验,流量设置为150,300,450,600,750,900 mL/min,分别进行排水、饱和、渗流3种水文状态的模拟试验。结果表明:(1)干热河谷冲沟发育区土壤砂粒含量明显高于粉粒和黏粒,占50%以上,土壤有机质(SOM)和全氮(TN)含量较低;(2)不同活跃程度冲沟土壤机械组成、有机质含量之间均存在显著差异,且随着冲沟稳定性增加,土壤砂粒含量呈逐渐降低趋势,土壤粉粒、黏粒、SOM、TN含量则呈不同程度的增加趋势;(3)在不同近地表水文状态下,土壤Kr值(s/m)均随冲沟稳定性的增加而呈递减趋势,表现为Kr(活跃型)>Kr(半稳定型)>Kr(稳定型),而不同活跃度冲沟土壤临界剪切力τc值之间具有一定差异性,但无明显规律;(4)冲沟不同部位土壤Kr值之间也具有显著的空间异质性,表现Kr(集水区)

Erodibility and Main Influencing Factors of Soil Rill in Gully Development Area of Dry-hot Valley

In order to find out the difference of soil rill erodibility(Kr value)under different near-surface hydrological conditions in different spatial parts of gullies with different active degrees in dry-hot valleys of China,different active gullies were selected in Yuanmou County of Yunnan Province,and soil samples of different spatial parts(upstream catchment area,gully wall and gully bed)were collected,and theVtype rill simulation scour device was used to carry out drainage scour experiment under three hydrological conditions(drainage,saturation and seepage),the flow rates were set as 150,300,450,600,750 and 900 mL/min.The results showed that:(1)In gully development area of dry-hot valley,the content of soil sand was significantly higher than that of silt and clay,accounting for more than 50%,and the content of soil organic matter(SOM)and total nitrogen(TN)was relatively low.(2)There were significant differences in mechanical composition and organic matter content among gullies with different active degrees,as the gully stability increased,the soil sand content gradually decreased,while the content of silt,clay,SOM and TN increased.(3)Under different near-surface hydrological conditions,as the gully stability increased,the soil rill erodibility(Kr value,s/m)of gully decreased,which followed the order of Kr(active type)>Kr(semi-stable type)>Kr(stable type).In addition,an obvious difference in soil critical shear force(τc,Pa)appeared in gullies with different activity degrees,while no obvious change tendency could be found.(4)Significant differences in Kr values could be found in the different parts of gully,which followed the order of Kr(upstream catchment area)