丹江口库区不同降雨类型下典型植被措施的水土保持效应

Effects of Typical Vegetation Measures on Soil and Water Conservation Under Different Rainfall Regimes in Danjiangkou Reservoir Area

为了进一步研究丹江口库区不同降雨类型下植被措施控制土壤侵蚀的效果,以丹江口库区典型生态修复小流域为研究对象,采用坡面径流小区观测法,基于长期野外原位监测的降雨和径流泥沙数据,以裸地为对照,研究不同降雨类型下典型植被恢复措施[柏树林(Cupressus funebris,CF)、枇杷林(Eriobotrya japonica,EJ)和紫花苜蓿草地(Medicago sativa,MS)]对坡面产流产沙和土壤侵蚀的影响,分析植被措施的水土保持效应对降雨类型的响应特征。结果表明:(1)中历时、中雨量、小雨强降雨(雨型Ⅲ)是研究区常见的降雨类型,短历时、小雨量、大雨强降雨(雨型Ⅰ)和长历时、大雨量、中雨强降雨(雨型Ⅱ)发生的频率相对较低,但雨型Ⅰ所导致的土壤侵蚀最为严重,占总侵蚀量的46.79%以上,降雨量和最大30 min雨强(I 30)是控制该区域土壤侵蚀的关键降雨因子。(2)植被措施均具有显著的水土保持效应,减流减沙效益依次为紫花苜蓿草地>柏树林>枇杷林。相比于裸地,紫花苜蓿草地径流系数减少54.07%,含沙量减少50.80%,土壤侵蚀量减少65.47%,而枇杷林的径流系数、含沙量和土壤侵蚀量仅分别减少30.60%,36.21%,45.42%。植被措施在雨型Ⅲ下的水土保持效应最优,以紫花苜蓿草地效果最好,土壤侵蚀的减少量可达87.98%,而在雨型Ⅰ条件下稍差,其中柏树林的效果相对较好,侵蚀减少量为65.25%;植被措施的减流效益随着降雨量的增加逐渐降低,减沙效益则随着I 30的增加而降低。当I 30<41 mm/h,紫花苜蓿草地的减沙效果较佳;当68.8 mm/h>I 30>41 mm/h,柏树林的减沙效果相对较好,但低于41.55%。研究结果对于丹江口库区水土保持及资源可持续利用具有重要指导意义。

In order to further study the effect of vegetation measures on soil and water conservation under different rainfall regimes,this study takes the typical ecological restoration watershed in Danjiangkou reservoir area as the research object and adopts the slope runoff plot observation method,to study the effects of typical vegetation restoration measure[Cupressus funebris(CF),Eriobotrya japonica(EJ),Medicago sativa(MS)]on runoff coefficient,sediment concentration and soil erosion amount in the slope under different rainfall regimes based on the rainfall,runoff and sediment data monitored in situ of long term field taking bare land as the control.The response characteristics of soil and water conservation effects of vegetation measures to different rainfall regimes were analyzed.The results are as follows:(1)Rainfall regimeⅢcharacterized by medium-duration,medium-rainfall and low-intensity was the most common type in the study area,while short-duration,low-rainfall and high-intensity rainfall(Rainfall regimeⅠ),and long-duration,high-rainfall and medium-intensity rainfall(Rainfall regimeⅡ)occurred relatively infrequently.But the soil erosion caused by Rainfall regimeⅠwas the most serious,accounting for more than 46.79%of the total erosion.Besides,the rainfall depth and maximum rainfall intensity of 30 min(I 30)were the key rainfall factors controlling soil erosion in the study area.(2)All vegetation measures had significant effects on soil and water conservation,and the benefits of runoff and sediment reduction were in the order of MS>CF>EJ.Compared to the bare land,MS decreased the runoff coefficient,sediment concentration and soil erosion by 54.07%,50.80%and 65.47%,respectively,while EJ reduced the runoff coefficient,sediment concentration and soil erosion by 30.60%,36.21%and 45.42%,respectively.The soil and water conservation effect of vegetation measures was the best under rainfall regimeⅢ,with the best effect of MS,the reduction of soil erosion reached 87.98%;while it was slightly weaker under rainfall regimeⅠ,among which the effect of CF was relatively better,with the reduction of erosion was 65.25%.Furthermore,the reduction benefit of runoff coefficient for vegetation measures gradually decreased with the increase of rainfall depth,the reduction benefit of sediment concentration decreased with the increase of I 30.The Medicago sativa measure had the better sediment reduction effect at I 30<41 mm/h,while CF had the better sediment reduction effect at 68.8 mm/h>I 30>41 mm/h,but lower than 41.55%.The results have important guiding significance for soil and water conservation and sustainable utilization of resources in the Danjiangkou reservoir area.