中文摘要：

植被恢复是防治崩岗侵蚀的重要方法,为研究植物根系对崩岗洪积扇土壤水分状况的影响,以崩岗洪积扇上种植的深根系巨菌草和浅根系宽叶雀稗为研究对象,对其分层取样后,用环刀法测定土壤的密度、孔隙度和最大持水量等物理性质,计算土壤蓄水能力,并用WinRHIZO根系分析系统,测定根长和密度等参数。结果表明：巨菌草和宽叶雀稗的各根系特征指标,均随土层深度的增加而减小,巨菌草各根系指标均大于宽叶雀稗;有植被覆盖下的土壤密度均小于裸地,植被覆盖下土壤总孔隙度和毛管孔隙度均大于裸地,且随土层深度的增加而减小;有植被根系的土壤饱和蓄水量和毛管蓄水量均比裸地高,且与裸地差异显著;在土壤表层,宽叶雀稗增加土壤孔隙性和土壤保水能力大于巨菌草,而在土壤中深层,则巨菌草大于宽叶雀稗;根系改善土壤性质的能力,主要取决于其根长密度和根系总表面积,直径小于0.5 mm的根系是影响土壤水分的最主要因子。研究植物根系对改良土壤水分状况的影响,以期为崩岗侵蚀防治中植被种类的筛选和推广提供依据。

英文摘要：

[Background] Alluvial is an important part of collapsing gully,as a type of disturbed soil,alluvial feature high contents of gravel,sand,and loose materials,so that they are often weak in structure,low in cohesion and high in erodibility.Alluvial may bring hazards to ecological environment.Plant is the key to control soil and water loss.Planting vegetation on the alluvial can effectively reduce erosion and water conservation,increase stability of soil structure and soil water storage ability.[Methods]Two typical herbs Pennisetum sp.（deep-root system） and Paspalum wettsteinii（shallow-root system）,which were planted in the alluvial soil,were chosen as the research object to analyze the effects of plants＇ root systems on the alluvial soil moisture.Soil samples were collected by layering samplingalong the root,and soil physical properties including soil bulk density,porosity and maximum moisture capacity etc.were tested by cutting ring method,which were used to calculate the soil water storage capacity.In addition,the roots were separated from undisturbed soil samples,which were collected by big cutting ring（the inner diameter of 9.8 cm and 5.0 cm high）.Root system parameters such as root length density,total surface area,total volume,average diameter,etc.were measured by WinRHIZO root analysis system.[Results] The indexes of root system characteristics of Pennisetum sp.and P.wettsteinii decreased with the increase of soil depth,all root indexes of Pennisetum sp.were greater than those of P.wettsteinii.Vegetation cover decreased the soil bulk densities compared to bare land,also the soil total porosity and capillary porosity of soil with vegetation covers were greater than those of bare land,decreasing with the increase of soil depth.In addition,plant root system increased the soil saturated water storage and capillary water storage,which were significantly different from those of bare land,so that showed the soil with root systems had a better effect on the soil water conservation than that of bare soi