The Mechanism And Model Optimization Of The Vegetation For Soil Erosion Resistance In Rolling Hill Regions With Black Soil

Slope farmland and bare gully-slope,as the main sediment source,are widely concerned considering soil erosion control in rolling hill regions with black soil of Northeast China.However,the key control technologies including vegetated earth bund technology and slope vegetation unavoidably cause the farmers'economic loss and thus take a risk to the destruction by the local farmers.The failure of these technologies threatens the food security and hinders the sustainable development of ecological agriculture in China.Currently,the urgent task of soil erosion control is to detect the mechanism of vegetation for soil erosion resistance and address an optimal species selection and allocation model with greater erosion-control and higher economic benefit.However,the relative study still be under discussion.Therefore,an observation of runoff and soil loss under natural rainfall,an artificially simulated rainfall experiment,and in situ scouring experiments were conducted on slope farmland,earth bund and gully,respectively.The effect of grain-feed crops type on the reduction of runoff and soil loss was detected,the protection of vegetation on earth bund and its model optimization was evaluated,and the response of runoff dynamics to the vegetation on gully slope was confirmed.This study provides a scientific reference and technical support for soil erosion control of slope farmland and gully slope in rolling hill regions with black soil of Northeast China.The main results were as follows:(1)In growing seasons,the total runoff of bare land was 95.3 mm,and the maximum and minimum values were in July(42.3%)and September(4.2%),respectively,which were mainly affected by rainfall and rainfall duration.Compared to bare land,the runoff reduction of five grain-feed crops can reach 21.5%–69.3%.The runoff reduction five grain-feed crops is as following:bromegrass>alfalfa>wheat>maize>soybean.In the same month,the runoff was mainly affected by plant coverage.In different months,the runoff of different grain-feed crops was affected by the rainfall characteristics and grain-feed crop types,and the influence of rainfall characteristics was greater.In growing seasons,the total soil loss of bare land was622.2 g m^-2,and the maximum and minimum values were in July(66.1%)and May(0.6%),and was mainly affected by rainfall erosivity.Compared to bare land,the soil loss reduction of five grain-feed crops can reach 54.1%–77.0%.The soil loss reduction of five grain-feed crops is as following:bromegrass>alfalfa>maize>soybean>wheat.The soil loss was mainly controlled by rainfall erosivity,canopy and root mass density.The reductions of runoff and soil loss of two forages were significantly higher than those of the three crops.Therefore,suitable conversion of farmland to forage is helpful to alleviate the aggravation of soil erosion of slope farmland in the Mollisol region of Northeast China.(2)Compared to the bare bund,vegetation growing on earth bund reduced runoff and soil loss by 15.3%–62.5%and 79.4%–93.8%,respectively.Of which,Medicago sativa,Rheum rhaponticum,Corylus heterophylla and Acanthopanax senticosus showed higher runoff and sediment reduction benefits than natural grass,while Ribes nigrum and Physalis peruviana showed lower runoff and sediment reduction benefits than natural grass.Runoff and soil loss were significantly affected by the diverse community(P<0.001),especially negatively controlled by plant coverage(P<0.01).The biomass of legume herb exhibited a higher negative-correlation with runoff(P<0.01)than the whole vegetation(P<0.05),however,plant diversity and roots had no significant effects on runoff and soil loss(P>0.05).Compared to the average farmland economic benefits,Corylus heterophylla,Ribes nigrum,Acanthopanax senticosus and Physalis peruviana improved economic benefits by 1.1–9.9 times,while Rheum rhaponticum and Medicago sativa decreased economic benefits by22.5%and 32.5%,respectively.Integrating these above-mentioned factors,Corylus heterophylla and Acanthopanax senticosus with Medicago sativa are highly recommended for controlling soil erosion of earth bund and increasing economic income.(3)The flow hydrodynamic characteristics were significantly affected by vegetation characteristics.For vegetated slopes,flow velocity,stream power,and unit stream power decreased by 42%–67%,0–18%,and 44%–68%,respectively,while flow depth,shear stress,the Darcy-Weisbach friction coefficient and Manning coefficient increased by 55%–150%,69%–156%,4–21 times and 1–4 times,respectively.Changes in the seven flow characteristic parameters were significantly influenced by vegetation coverage,above-ground biomass,root mass density and litter biomass(P<0.05).Vegetation planted on the gully slope functioned well on slope protection,and this function was significantly affected by vegetation characteristics.Compared to the bare slope,the five vegetation communities decreased runoff and soil loss by 19%–30%and 78%–97%,respectively.The runoff and soil loss decreased with the increase of vegetation coverage,root density and litter,and vegetation with tap roots was more effective in controlling gully bank erosion.Thus,the mixed-sowing vegetation community consisted of Dactylis glomerata,Festuca arundinacea,Uraria crinita,Medicago sativa(25:25:25:25)is perfectly acceptable for gully bank protection in the Mollisol region of Northeast China.