Study On The Benefits Of Water And Sand Reduction On The Slope Of Plant Hedges

With the rapid development of China’s economy and society,soil erosion has become an urgent ecological and environmental problem in China.As one of the key areas of soil and water loss in China,it is urgent to take biological measures of soil and water conservation to control slope water erosion.As an effective biological measure of soil and water conservation,plant buffer zone has many advantages,such as small land occupation,quick effect and low cost.It has been widely used in the control of soil and water loss on slope.Exploring the benefits of slope runoff and sediment reduction with different configurations of plant buffer zones can provide a theoretical basis for the optimization of the configuration of plant buffer zones in Sloping Farmland in rocky mountainous areas of North China.In this paper,under the condition of runoff scouring,the configuration of different plant buffer zones on the slope（upper slope position S,middle slope position Z and lower slope position X）is taken as the research object.The process of runoff and sediment yield,slope velocity and runoff width are observed,the influence of plant buffer zones in different growth periods（June to September）on runoff and sediment yield on the slope is analyzed,and the influence of different configuration of plant buffer zones on the benefit of runoff and sediment reduction on the slope is clarified.The main conclusions are as follows:（1）Runoff yield characteristics of slope with different plant buffer zonesWith the increase of growth period（June September）,the initial runoff production time of different plant buffer zones shows a downward trend,and the difference of initial runoff production time between plant buffer zones at different slope positions is small.The effect of plant buffer zone on Soil and water conservation gradually increases with the time of plant buffer zone;Under different scouring intensities,the variation trend of flow rate with time on slopes with different plant buffer zones（S,Z,X）and control（CK）is basically similar,showing that with the extension of scouring duration,it rises rapidly in the first 0～5 minutes,and tends to be stable or fluctuate up and down in 4～10 minutes.On the 5°slope,under the scouring flow of 0.15 L/s,the flow reduction of Z₅ is the most in August,reaching 12.86L;Under the scouring flow of 0.25 L/s,X₅ reduces the flow most in September,reaching 19.73L;Under the scouring flow of 0.35 L/s,the flow reduction of X₅ is the most in August,reaching 18.07L.On the 10°slope,under the scouring flow of 0.15 L/s,the flow reduction of Z₁₀ is the most in August,reaching 15.04L;Under the scouring flow of 0.25 L/s,the flow reduction of Z₁₀ is the most in August,reaching 31.65L;Under the scouring flow of 0.35 L/s,X₁₀ reduces the flow most in September,reaching 33.32L.On the 15°slope,under the scouring flow of 0.15 L/s,the flow reduction of Z₁₅ is the most in August,reaching 11.19l;Under the scouring flow of0.25 L/s,the flow reduction of Z₁₅ is the most in September,reaching 22.09L;Under the scouring flow of 0.35 L/s,the flow reduction of Z₁₅ is the most in August,reaching 24.42L.On the slope with plant buffer belt,the flow velocity of water passing through the buffer belt has an obvious decreasing trend.From the flow velocity data,when the plant buffer belt is arranged on the downhill position（X）,the flow velocity decreases significantly between the plant buffer belts,and the flow reduction effect of the plant buffer belt is strong.（2）Characteristics of sediment yield on slope of different plant buffer zonesWith the increase of scour time,the sediment yield rate on the slope presents a multi-peak,multi-valley and fluctuating variation law with time.With the increase of the growing period of amorpha fruticosa plant buffer zone,the root and stem of the plant buffer zone became stronger and stronger,and its mechanical blocking effect on runoff and sediment was gradually enhanced.At the same time,the roots of the plant buffer zone consolidated the soil.During the whole growing period,the soil and water conservation effect of the plant buffer zone became more and more prominent.Through the experimental data,it can be found that when the plant buffer zone is arranged in the downslope position（X）,the sediment reduction benefit is stronger than that in the upslope position（S）and middle slope position（Z）.From the perspective of time scale,sediment reduction reached 196.75g in August X₅ on 5°slope at 0.15 L/s scour flow from June to September during the growing season of plant buffer zone.Under the flow rate of 0.25L/s,sediment reduction of X₅ in September was 356.82 g.Under the condition of 0.35 L/s scour flow,X₅ sediment reduced the most in September,reaching 544.5 g.At 10°slope and 0.15 L/s scour flow,sediment reduction of X₁₀ in August was the highest,reaching 314.82 g.Under the condition of 0.25 L/s scour flow,the sediment reduction of X₁₀ in August is the largest,reaching718.85g.Under the condition of 0.35 L/s scour flow,the sediment reduction of X₁₀ in September is the largest,reaching 1305.55g.During the whole test period on the 15°slope,the sediment reduction in September X₁₅ was the largest at 312.03g at 0.15L/s scour flow.Under the condition of 0.25 L/s scour flow,the sediment reduction amount of Z₁₅ in September was the largest,reaching 1330.77g.Under the condition of 0.35 L/s scour flow,Z₁₅ sediment reduced the most in September,reaching 1749.29g.（3）benefits of reducing flow and sediment on slope with different plant buffer zonesOn the 5°slope,when the scour intensity was 0.15 L/s in August,the plant buffer zone（Z₅）in the middle slope had the highest flow reduction efficiency,reaching 17.7%.On the 10°slope,with a scour intensity of 0.25 L/s in August,the flow reduction benefit of plant buffer zone(Z₁₀)in the middle slope was the highest,reaching 23.66%.On the 15°slope,with a scour intensity of 0.25 L/s in September,the flow reduction benefit of plant buffer zone(Z₁₅)in the middle slope was the highest,reaching 15.59%.On the 5°slope,at the flow rate of 0.25 L/s in September,the plant buffer zone（X₅）at the slope position had the highest sediment reduction benefit,reaching 34.5%.On the 10°slope,when the scour flow was 0.25 L/s in August,the sediment reduction benefit of plant buffer zone(X₁₀)was the highest,reaching 47.81%.On the15°slope,at the flow rate of 0.25 L/s in August,the plant buffer zone(X₁₅)at the downslope position achieved the highest sediment reduction efficiency,reaching 31.67%.It can be seen that when plant buffer zone is arranged in middle（Z）and lower（X）slope,the flow reduction benefit is better（15.59%-23.66%）.In terms of sediment reduction benefit,the best sediment reduction benefit of slope plant buffer zone is more significant（31.67%～47.81%）when the plant buffer zone is located in the downhill position（X）.In different growth periods,soil water content showed the following pattern:August>September>June>July.There were differences in soil water content at different slope positions,and the overall pattern was:downhill position>middle slope position>uphill position.When the buffer zone of amorpha fruticosa was placed in the downslope position,its water retention capacity was stronger than that of middle slope position and upslope position.The water content on the 5°,10°and 15°slopes at the X slope position in August is 17.95%,18.62%and 15.06%,respectively.