红黏土侵蚀劣地集水区30年植被恢复中的水沙特征

为探究红黏土侵蚀劣地植被恢s复的水土保持效益,在自然降雨条件下,对红黏土区裸地对照及植被恢复的2个自然集水区进行长期降雨径流泥沙监测,得到30年的产流产沙数据.结果表明:1)植被恢复第6年裸地对照和恢复林地的产流差距显著,8年后恢复林地基本不再产沙.年内产流产沙集中在雨季4-6月,植被的减流和减沙效益分别超过40％和90％.在次降雨尺度上,植被能够显著降低径流泥沙曲线斜率,在降雨量相同的条件下减小地表产流产沙量.2)降雨过程产流产沙与降雨强度I60变化趋势一致,呈多峰型,总体上恢复区延缓产流1h以上,产流峰值减小67％ ～ 83％,中雨条件下植被延缓径流和降低产流峰值的效益最好.3)恢复林地径流中全N、全P、全K流失量分别减少54.62％、57.53％、56.46％,次降雨过程中全N和全K流失质量浓度高于全P浓度,且随径流过程波动较大.植被恢复后的红黏土集水区产流产沙及养分流失显著减少,水土流失得到有效控制.

Characteristics of runoff and sediment yield of catchment area under 30 years vegetation restoration in red clay erosion badland

Background]The red soil region is one of the typical areas suffering serious soil erosion in southern China.The red clay badland is a kind of seriously eroded degradation and is still one of the main obstacle factors in enhancing regional soil quality and ecosystem function.Thus,suitable management is urgently needed,and systematic analysis and evaluation should be carried out.This paper is therefore conducted to evaluate the soil and water conservation benefit of the vegetation restoration measures in red clay badland.Methods] Two field plots were built according to the natural drainage boundary 30 years ago.One is in the bare land as control and the other is vegetation restoration treatment.Runoff and sediment generation were monitored continuously under the natural rainfall condition.According to the long-term field plot monitoring data and rainfall event process information,the dynamic of runoff and sediment yield can be quantitatively described and the benefits of vegetation restoration can be evaluated.Results] 1) The runoff yield showed significant differences between the bare land and vegetation treatment at the 6th year of restoration.Sediment yield was approximately zero in the vegetation recovered plot after 8 years.The dynamic characteristics of both runoff and sediment yield throughout a year followed the same trend as rainfall,concentrating from April to June.The efficiencies for vegetation restoration in reducing runoff and soil loss were more than 40％ and 90％ respectively.The vegetation significantly reduced the coefficients of regression curves,meaning that the runoff and sediment yield in the restored land tended to be less than that of the bare land with the same precipitation.2) The dynamic of the runoff and sediment yield during a rainfall event process showed multi peak curves and consistent with the trend of the rainfall intensity (I60max).The time to runoff and sediment yield in the vegetation treatment generally 1 hour delayed compared with the bare land.Meanwhile,the peak runoff and sediment in the restored land were also delayed and decreased by 67％-83％.The benefit of vegetation on reducing peak value of the runoff under moderate rain was better than that under rainstorm or heavy rain.3) Comparing with the bare land,the loss of total nitrogen (TN),total phosphorus (TP) and total potassium (TK) in the restored land were reduced by 54.62％,57.53％,and 56.46％ respectively.During a rainfall and runoff process,the total losses of TP were obviously lower than the TN and TK.The concentration of TN and TK in rainfall process fluctuated and was higher than TP which was relatively stable.Conclusions] The rapid restoration of vegetation can effectively control the surface runoff and sediment yield,delay runoff generation process and reduce peak flow.Meanwhile,recovery measures can significantly reduce nutrient loss in runoff and sediment.Therefore the vegetation restoration can be applied in local ecology recover and soil management.This study can provide a scientific basis for the assessment of the water and soil conservation benefit of vegetation restoration in red clay badland.