典型喀斯特区侵蚀性降雨特征及坡面生物措施水土流失防控效应

降雨类型和生物措施是坡面水土流失的重要影响因素。为研究喀斯特区降雨类型和不同坡面生物措施共同作用下的水土保持效益,以贵州蚂蟥田小流域水土保持监测站2014—2018年5年的径流小区实测数据为基础,分析了112场次的侵蚀性降雨特征,并以降雨量、降雨历时、平均降雨强度为指标对其进行分类。同时,分析了不同侵蚀性降雨类型下6个生物措施径流小区的产流产沙量,生物措施包括自然恢复草地、水土保持林(水保林)和经济果木林(经果林)。结果表明,侵蚀性降雨可以分为3类,通过分析降雨侵蚀力和各生物措施坡面的产流产沙能力,得出降雨的侵蚀能力表现为B雨型(中历时、大雨量、中雨强)>C雨型(短历时、小雨量、大雨强)>A雨型(长历时、中雨量、小雨强),B和C雨型的产沙量占全年总产沙量的85%以上。侵蚀性降雨集中发生在5—10月,占全年总产沙量的92.6%和总产流量的93.2%;3种生物措施的产流产沙量大小为:自然恢复草地>水保林>经果林,水保林和经果林的侵蚀产流量差异不显著(P<0.05)。对比自然恢复草地,水保林和经果林均能够减少侵蚀达50%以上。此外,其削减能力与降雨类型有关,在不同雨型下两种林地的减沙能力为:A雨型>C雨型>B雨型。研究结果可为喀斯特地区以生物措施治理坡面水土流失提供参考。

Characteristics of Erosive Rainfall Patterns and Benefit of Soil and Water Conservation for Biological Measures on Slope in Karst Region

Rainfall patterns and biological measurement are important factors responsible for affecting soil and water loss on slope.To analysis the benefits of soil and water conservation affected by rainfall pattern and biological measurement in karst area,southwest China,where is the largest karst continuous distribution zone in the world,present study explored sediment yield and runoff based on measured data of runoff plots from 2014 to 2018,located in the Mahuangtian watershed,Guizhou province.Biological measurements included natural grassland(NG),soil and water conservation forests(SWF),and economic forests(EF).The characteristics of 112 erosive rainfalls were surveyed and classified,in terms of duration,amount of rainfall,and rainfall intensity.Simultaneously,sediment yield and runoff of 3 kinds of biological measurements affected by different rainfall pattern were analyzed.Results showed that the erosive rainfalls could be classified into 3 types.Based on the rainfall erodibility and actual sediment yield and runoff on slope,the order of rainfall erosivity capacity was:type B(featured with short duration,high amount of rainfalls,and medium rainfall intensity)>type C(featured with medium duration,low amount of rainfalls,and strong rainfall intensity)>type A(featured with long duration,medium amount of rainfalls,and weak rainfall intensity).Type B and C were the main rainfall patterns to cause sediment yield and runoff,which accounted for above 85%of total sediment yield.Rainfall pattern obvious influenced sediment yield and runoff.For the nearly amount of rainfall,the sediment yield and runoff positively related with amount of type B and C,which had stronger rainfall erosivity capacity.The erosive rainfall in the study area was concentrated from May to September,accounting for 93.3%of the total rainfall amount,92.6%of the total sediment yield,and 93.2%of runoff.The order of erosion and runoff capacity for 3 ecological measurements was:NG>SWF>EF.Compared of mean value of average soil erosion modulus in karst region of Guizhou,the 3 biological measurements had a smaller erosion modulus,and reduction rates were more than 90%.The differences between SWF and EF were non-significant(P<0.05).Compared with sediment yield of NG,the sediment reduction ratios of SEF and EF were>85%.In addition,the reduction ratios of SEF and EF were related with rainfall patterns.The order of sediment reduction affected by rainfall pattern was:type A>type C>type B.The SWF had the best ability to conserve soil and water,while that was poorest for the NG.Therefore,the NG should be artificially enhanced to improve the capacity of soil and water conservation in karst region.Results of this study are useful for preventing soil and water loss with the help of ecological restoration measures in the karst region.