黄土区草本植被根系与土壤垂直侵蚀产沙关系研究

RELATIONSHIP BETWEEN HERBACEOUS ROOT SYSTEM AND VERTICAL SOIL SEDIMENT YIELD IN LOESS AREA

为了系统揭示植被根系对径流侵蚀产沙的影响,采用土钻法对草地植被根系分布特征进行系统调查,采用分层冲刷的方法对黄土高原草地土壤不同坡度、不同流量条件下的侵蚀产沙特征进行了研究。结果表明不同立地上的植被根系都表现出了随着土层深度增加而减少的趋势。分层冲刷的试验结果表明在土壤表层,植被根系对侵蚀产沙的影响是占主导地位的;而当土层超过一定深度后,根系的分布数量减少,不同流量和坡度下的深层土壤侵蚀产沙量明显增加,根系提高土壤抵抗径流侵蚀产沙的能力受到了限制。同时随着土层深度的不断加大,坡面上径流侵蚀的形态也在发生变化,逐渐从面蚀向细沟侵蚀发展。结合对草地植被根系生物量垂直分布特征的研究,证明土壤侵蚀产沙的这种变化是与草本植被根系的分布特征密切相关的。通过进一步分析植被根系分布特征和土壤垂直侵蚀产沙之间的联系,建立了草地植被根系生物量与土壤垂直侵蚀产沙特征之间的定量关系。

Current knowledge about root morphology and its impacts on soil erosion is limited and, therefore, detailed analyses of root system in controlling soil erosion are needed. In order to determine the effects of root system on soil erosion quantitatively, root investigation and stratified runoff scouring were conducted in field. The distribution of vertical root biomass on three sites decreased with the increase of soil depth in a similar manner. Most roots were concentrated in surface soil, and decreased to less than 0.2 kg· m^- 3 in soil below the depth of 40 cm. There was no significant difference in root biomass on the same soil depth from different points. Results from stratified runoff scouring on different soil depths in the field indicated that, on the surface soil layer, the existence of root could effectively improve soil resistance to runoff erosion, and its effect on sediment yield was dominant. While in deeper soil, sediment yield increased with the decrease of root distribution, and was more related to slope gradient, runoff discharge and soil properties. In addition, with the progress of runoff scouring, the form of soil erosion changed from sheet erosion to rill erosion. Investigation of the root distribution patterns revealed that the vertical sediment yield was closely related to root distribution characteristics. Further analysis of the root distribution pattern and the vertical sediment yield allowed establishment of a quantitative relationship between root biomass and vertical sediment yield.