黄土塬沟壑区典型植被沟头土壤渗透性和抗剪强度特征

Infiltration and shear strength characteristics of gully heads soil of typical vegetation on the gullied Loess Plateau,Northwest China

沟头是沟蚀的主要活跃部位,严重影响沟头溯源侵蚀发生。为明确典型植被沟头根系分布及土壤物理和力学特征,本研究以自然植被恢复沟头和人工植被恢复沟头为对象,分析0~1m不同土层土壤入渗、根系分布以及根-土复合体物理和力学性质特征。结果表明:不同植被沟头土壤容重和总孔隙变异较小,容重在1.10~1.37g·cm^(3),土壤总孔隙在48.3%~58.4%;各入渗指标总体随土层增加呈减小趋势,自然植被恢复沟头不同土层入渗速率在20~30min趋于稳定,人工植被恢复沟头在40min趋于稳定,人工植被恢复沟头的稳定入渗速率、平均入渗速率总体大于自然植被恢复沟头;根长密度、根表面积密度、平均直径均随土层的增加呈降低趋势,除20~40cm土层,自然植被恢复沟头的根长密度、根表面积密度、平均直径皆小于人工植被恢复沟头,两种植被沟头根系主要由0~0.5mm根系构成,占总根长的84.2%~93.6%;在垂直深度上,随着含水率的增加,黏聚力随土层由上至下迅速线性衰减,变化范围为0.42~22.67kPa,在相同含水率条件下,人工植被恢复沟头平均黏聚力总体大于自然植被恢复沟头。本研究揭示了植被对沟头溯源侵蚀的阻控作用,可为该区域有效防治水土流失提供科学基础。

Gully head is the main active part of gully erosion,which seriously affects the occurrence of gully headcut erosion.To investigate root distribution and soil physical and mechanical characteristics of typical vegetation gully head,we analyzed the infiltration,root distribution,physical and mechanical properties of soil-root complex of soil in different layers(0-1 m)in natural restoration gully head and artificial restoration gully head.The results showed that the variability of soil bulk and total porosity among different vegetation gully heads was low,with bulk density ranging from 1.10 to 1.37 g·cm^(3)and total porosity ranging from 48.3%to 58.4%.Infiltration index of different vegetation gully heads generally decreased with increasing soil depth.The infiltration rate of different soil layers in natural restoration gully head tended to stabilize in 20-30 min,while that of artificial restoration gully head tended to stabilize in 40 min.The infiltration capacity and average infiltration rate of artificial restoration gully head were generally higher than those of natural restoration gully head in all soil layers.Root length density,root surface area density,and average diameter all tended to decrease with increasing soil depth.Except for the 20-40 cm soil layer,root length density,root surface area density and average diameter of natural restoration gully head were all lower than those of artificial restoration gully head.Root system of both vegetation gully heads mainly consisted of 0-0.5 mm roots,accounting for 84.2%-93.6%of the total root length.In the vertical depth,with the increases of water content,the cohesion force decreased linearly with the deepening of soil layer,ranging from O.42 to 22.67 kPa.The average cohesion force of artificial restoration gully head was higher than natural restoration gully head at each level of water content.The study revealed the effects of vegetation on the gully head cut erosion,which could provide scientific basis for the effective prevention and control of soil erosion in the region.