黄土高原沟壑区沟头植被根系垂直分布及其对土壤抗侵蚀性的影响

【目的】探明沟头植被根系垂直分布及其对土壤抗侵蚀性的影响，为沟蚀防治中植被措施优化配置提供理论依据。【方法】以不同植被覆盖(杂草(农地)、冰草、铁杆蒿、苜蓿)沟头为研究对象，通过原状土冲刷试验明确沟头土壤抗冲性特征。采用扫描分析法、ZJ型应变控制式直剪仪等分析和测定根系特征及根-土复合体力学、理化性质。【结果】(1)各植被沟头根系在土壤中分布特征差异明显，根系特征指标(根重密度、根长密度、根表面积密度、根体积密度)总体上呈现冰草地最大，其次为苜蓿地、铁杆蒿地，农地最小；垂直深度上，农地沟头土壤中根系各指标均随土层加深而减小，冰草、铁杆蒿和苜蓿地沟头土壤中根系各指标整体上则表现为先减小后增大的变化趋势。各植被根系以<0.5 mm径级根系为主。(2)各植被沟头土壤容重变异性较小，在1.17—1.37 g·cm^-3之间变化。>0.25 mm水稳性团聚体含量呈现出农地和冰草地大于铁杆蒿地和苜蓿地。(3)各植被沟头土壤黏聚力平均值苜蓿地为12.75 kPa、冰草地9.05 kPa、铁杆蒿地8.60 kPa、农地7.25 kPa；在垂直深度上，农地、冰草地和苜蓿地...

Vertical Distribution of Vegetation Roots and Its Influence on Soil Erosion Resistance of Gully Heads on the Gullied Loess Plateau

【Objective】The vertical distribution of gully vegetation root system and its effect on soil erosion resistance were explored, so as to provide a theoretical basis for optimizing the allocation of vegetation measures in gully erosion control. 【Method】 In this paper, the gully heads covered with different vegetation (weeds (farmland), Agropyron cristatum, Artemisia gmelinii, and Medicago sativa) were taken as the research object. The scouring experiment of undisturbed soils was carried out to determine the soil anti-scouribility. Moreover, the root characteristics and mechanical and physiochemical properties of root-soil complex were measured using root scanner and ZJ series strain controlled direct shear test apparatus, and so on, respectively. 【Result】(1) The root distribution characteristics at the gully head varied among different vegetation types. Agropyron cristatum had the greatest root characteristic indexes (root weight density, root length density, root surface area density, and root volume density), followed by alfalfa, Artemisia, and weeds in farmland. In addition, the root indexes in the gully head soil of farmland decreased with the deepening of soil layer, while those of Agropyron cristatum, Artemisia gmelinii and Medicago sativa firstly decreased and then increased with the deepening of soil layer. Furthermore, the roots with the diameter of <0.5 mm dominated in the root system of each vegetation. (2) The variability of soil bulk density among different vegetation type was low, ranging from 1.17 g·cm^-3 to 1.37 g·cm^-3. The contents of >0.25 mm water-stable aggregates of farmland and Agropyron cristatum land were higher than that of Artemisia gmelinii land and Medicago sativa land. (3) The average soil cohesions of gully heads under different vegetation types were as follows: 12.75 kPa for Medicago sativa land, 9.05 kPa for Agropyron cristatum land, 8.60 kPa for Artemisia gmelinii land, and 7.25 kPa for farmland, respectively. Additionally, the soil cohesion of the farmland, Agropyron cristatum land, and Medicago sativa land decreased first and then increased with the deepening of soil layer, while that of Artemisia gmelinii land showed a decreasing trend in the depth of soil. (4) The average anti-scouribility coefficients of 0-100 cm soil at the gully head under different vegetation types were as follows: 39.31 L·g^-1 for Medicago sativa land, 25.49 L·g^-1 for Agropyron cristatum land, > 22.39 L·g^-1 for farmland and 14.75 L·g^-1 for Artemisia gmelinii land. Moreover, the soil anti-scouribility coefficient of the 0-20 cm soil layer, varying between 34.91 and 53.30 L·g^-1, was larger than that of the lower soil layers. 【Conclusion】 The combination of plants with tap roots and the plants with fibrous roots was suggested for the control of gully head erosion, and the results provided a theoretical basis for the research of gully headcut erosion and gully erosion control.