Characteristics Of Ephemerial Gully Erosion And Its Effects In Typical Black Soil Region

Northeast China is China's granary,as it produces 60%of this country's commodity grain.However,severe soil erosion is threatening its grain production sustainability.Ephemeral gully is one of the important representations of soil erosion,since it not only reduces farmland area but also increases sheet erosion.Research period on ephemeral gully erosion in the Black soil areas of Northeast China is short,and there are few researches on ephemeral gully erosion effect on the farm production.In this paper,the Guangrong Village in the Heilongjiang Province,typical rolling hill region,was selected to carry out ephemeral gully erosion research.Distributions and characteristics of ephemeral gully erosion in Guangrong village were investigated through remote sensing interpretation and field measurements.The development process,spatial distribution of soil moisture and bulk density was studied on three typical ephemera gullies(A1?A3).The spatial morphological changes of fourteen ephemeral gullies(B1?B14)were investigated using drone stereo photography.The effect of ephemeral gully on the farmland yield was studied were measured based on nine ephemeral gullies(C1?C9).Main research results were as follows:1)The length of ephemeral gully and the upcatchment area showed a significant positive correlation.The upcatchment area and the degrease ratio were the main factors that determined the length of the ephemeral gully.Ephemeral gully mostly appeared in farmland catchment with larger slopeness and smaller area.In the farmland catchment with less slopeness and area,the shearing force of the water in the furrow was much less than the shear stress of the ridge and the ephemeral gully was not tending to occur.Comparing with traditional tillage,farmland with contour tillage was more prone to be effect by ephemeral gully erosion.2)Rainfall and snowmelt erosion were important driving external forces for ephemeral gully erosion in the farmland,and rainfall runoff was the main trigger.The total runoff and sediment within snow-melting period was much less than that within rainfall p eriod.The soil loss by snowmelt erosion accounted for 0.26%,0%and 0.29%of total soil loss for A1?A3,respectively.3)The drone stereo photography results showed that average soil loss for rainfall runoff erosion in 2018 was 128 t per gully and for snow-melting erosion in 2019 was 86 per gully.The maximum and minimum topsoil depth reduce were 10.1 mm and 0.8 mm.4)Classical statistical analysis showed large difference for so il water content and bulk density within the catchment of the EG.For A1,the coefficients of variations of soil saturated water content and soil water holding capacity were between 10%and 100%with a medium-intensity variation,and those of soil mass moisture content,soil volume moisture content and bulk density were less than 10%with a weak variation.For A2,the coefficients of variations of soil saturated water content,soil mass moisture content and soil volume moisture content were with a medium-intensity variation,and those of soil water holding capacity and bulk density were with a weak variation.For A3,the coefficients of variations of soil saturated water content,soil water holding capacity and soil volume moisture content were with a medium-intensity variation,and those of soil mass moisture content and bulk density were with a weak variation.5)Geostatistical analysis showed large difference for soil water content and bulk density.The disturbance by cultivation was less than natural topo graphy,with strong spatial autocorrelation for A1 and A2.The soil water content and volume content of the ridges and ridges in the catchment area were also greatly affected.The variables were both affected by disturbances such as soil cultivation and natural topography,belonging to medium spatial autocorrelation.6)Ephemeral gully erosion affected soil infiltration rates within the catchment area.Initial infiltration rates of three ephemeral gullies of A1?A3 were generally in the range of 25-50mm/min,and stable infiltration rates were generally in the range of 0-10 mm/min.Initial infiltration rate and stable infiltration rate at the bottom of ephemeral gully were generally lower than those on upper catchment.Stable infiltration rate in June was g enerally higher than that in August and September.There was no significant difference in the average soil infiltration rate among three ephemeral gullies.7)Crop yields along ephemeral gullies were lower than those within the catchment area.Most of crop yields at the gully bank were higher than those values at the top and bottom of ephemeral gullies,and average yield at the bottom of ephemeral gully was significantly reduced.Crop yields at the bottom of ephemeral gullies of C1?C2 showed a reduction,between 2121 and11587 kg/hm~2.Most of crop yields at the gully bank showed increased production between 130and 4689 kg/hm~2.In total,the ephemeral gully in the farmland caused crop yield reduction,between 1377 and 16276 kg/hm~2.