农田浅沟中不同植物的水土保持效果和机理分析

为探究不同植物在东北黑土地区农田浅沟中的水土保持效果,建立裸坡(LP)和种植有紫花苜蓿(V₁)和马蔺草(V₂) 2种植物的坡面浅沟模型,通过在浅沟内模拟上方汇水,进行不同植物覆盖下的浅沟坡面水力侵蚀试验,分析产流产沙特征及水动力学参数时空变化特征。结果表明：(1)相同流量下产流时间为裸坡<紫花苜蓿<马蔺草,产流时间延长,下渗量明显增大,紫花苜蓿(61%)的减沙效果显著优于马蔺草(29%),但紫花苜蓿(33%)减流效果弱于马蔺草(38%)。(2)相同流量下,紫花苜蓿的水力摩擦系数(f)(2.3)高于马蔺草(0.8),同时紫花苜蓿的平均流速(u)略低于马蔺草,弗劳德数(Fr)表现为紫花苜蓿<马蔺草,平均雷诺数(Re)表现为紫花苜蓿<马蔺草,整体表现为紊流。(3)通过拟合函数分析,3组处理下雷诺数与流速和摩擦系数呈正相关,但函数关系略有差别;弗劳德数与摩擦系数呈负相关,均符合对数函数变化规律。产流率和产沙率的降低归因于植被覆盖增大径流受到的摩擦力,同时提高径流入渗率,并且紫花苜蓿的减流减沙效果优于马蔺草;随着流量增大,马蔺草...

Soil and Water Conservation Effect and Mechanism Analysis of Different Plants in Ephemeral Gully of Farmland

To investigate the effects of different plants on soil and water conservation in ephemeral gullies of agricultural fields in the black soil region of Northeast China, ephemeral gullies were modelled on bare slopes (LP) and slopes planted with both alfalfa (V₁) and Iris ensata Thunb (V₂). By simulating upper catchment, hydraulic erosion experiments were carried out on the slope surface of ephemeral gullies covered by different plants, and the characteristics of runoff and sediment yield as well as the spatial and temporal variation of hydrodynamic parameters were analyzed. The results showed that: (1) Under the same flow rate, the runoff generation time followed the order of LP < alfalfa < I. ensata Thunb, with significantly prolonged flow production and greater infiltration, sediment-reduction benefits of alfalfa (61%) was significantly better than that of I. ensata Thunb (29%), but the runoff reduction benefits of alfalfa (33%) was slightly weaker than that of I. ensata Thunb (38%). (2) Under the same flow rate, hydraulic friction coefficient (f) of alfalfa (2.3) was higher than that of I. ensata Thunb (0.8), while the average flow rate (u) of alfalfa was slightly lower than that of I. ensata Thunb, the Froude number (Fr) and the mean Reynolds number (Re) followed the order of alfalfa < I. ensata Thunb, and the overall flow was turbulent. (3) Analysis of the fitted functions showed that Reynolds number was positively correlated with flow rate and friction coefficient under the three sets of experiments, but the functional relationship was slightly different. Froude number was negatively correlated with friction coefficient, all in line with the law of logarithmic function change. The results showed that the reduction of runoff and sediment yield was due to the increase of friction and infiltration rate of the vegetation cover, and alfalfa was more effective in reducing runoff and sediment than I. ensata Thunb. With the increasing flow rate, the runoff and sediment reduction benefits of I. ensata Thunb decayed more rapidly than those of alfalfa. The critical flow rate for protection of I. ensata Thunb was 30~40 L/min, and alfalfa could meet the soil and water conservation needs at higher catchment flow.