黄土丘陵沟壑区多年生草地的保水固土效益

Effects of Perennial Grassland on Soil and Water Conservation in Hilly Region of Loess Plateau

[目的]探究草被在不同生长年限和不同降雨类型下的保水固土效益,为黄土区进一步开展生物水保措施提供理论依据。[方法]以绥德水土保持科学试验站辛店沟平沟墕苜蓿、草木樨和农地标准径流场1956—1960年汛期总降雨和汛期40场次降雨产流产沙监测数据为基础进行分析研究。[结果]（1）各观测年汛期总径流量和总产沙量大小顺序均为：牧草地〈农地,以农地为参照,苜蓿和草木樨径流场减水效益分别为20%~83%和11%~88%,二者减沙效益基本保持在50%以上;（2）采用K-Means聚类分析法,以次降雨量和最大30分钟雨强（I30）为聚类条件,将40场次降雨事件划分为雨量大雨强低的Ⅰ型、雨量小雨强大的Ⅲ型以及中等雨量中等雨强Ⅱ型。各径流场在Ⅲ雨型下产流产沙量最大,两种牧草地在Ⅱ雨型下减水效益最佳;（3）两种牧草地减水减沙效益随生长年限的变化而变化,且各径流场减水减沙效益主要受Ⅲ雨型影响,该雨型下牧草地减水效益随生长年限的增加而增加,减沙效益随生长年限先减小后增加。[结论]两种牧草均具有较好的减水减沙效益,而其减水减沙效益与雨型具有密切关系,不同时期,草地减水减沙效益并非同步。

[Objective]The effects of perennial grassland with different growing years and rainfall regimes on soil and water conservation were analyzed to provide a theoretical basis for the further development of biological engineering measures in hilly region of the Loess Plateau.[Methods]Data of total runoff sediment yield and 40 rainfall events collected from Suide Soil and Water Conservation Station from 1956 to 1960were used to analyze the effects of perennial grassland on soil and water conservation in hilly region of the Loess Plateau.[Results]（1）The observed total runoff and erosion modulus of grasslands were smaller than those of farmlands.Runoffs of alfalfa and Melilotus decreased 20%~83% and 11%~88% respectively,as compared with the corresponding values of farmlands.Sediment reductions of grassland and farmlands were both more than 50%.（2）Based on K-Means clustering,40 rainfall events were classified into three rainfall regimes according to the amount and intensity（30min）of rainfall：regimeⅠ had the characteristics of high rainfall,low intensity and occurred infrequently;regime Ⅱ had the features of medium rainfall,medium intensity and medium frequent occurrence;regimeⅢ had the features of less rainfall,high intensity and high frequent occurrence.A large proportion of runoff and soil loss was caused by rainfall regime Ⅲ.Water reduction of grasslands was observed the best in regimeⅡ of the three regimes.（3）Under regime Ⅲ,thebenefit of water reduction increased with the increase of grass growth period,and soil reduction was small in earlier growth years and then increased afterwards.[Conclusion]Grasslands grew with the two grasses both had the benefits of water and soil reduction.The benefit were closely linked with rainfall regime.The benefit of water reduction and soil reduction were not always coincided.