Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on segments was used to analyze the runoff data...Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on segments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and intensive precipitation, rill can be formed starting even at 15 m from the top of the slope.展开更多
Rills are frequently observed on slope farmlands and rill erosion significantly contributes to sediment yields. This paper focuses on reviewing the various factors affecting rill erosion processes and the threshold co...Rills are frequently observed on slope farmlands and rill erosion significantly contributes to sediment yields. This paper focuses on reviewing the various factors affecting rill erosion processes and the threshold conditions of rill initiation. Six factors, including rainfall, runoff, soil, topography, vegetation and tillage system, are discussed. Rill initiation and network are explored. Runoff erosivity and soil erodibility are recognized as two direct factors affecting rill erosion and other types of factors may have indirect influences on rill erosion through increasing or decreasing the effects of the direct factors. Certain conditions are necessary for rill initiation and the critical conditions are different with different factors. Future studies should be focused on 1) the dynamic changes of rill networks; 2) the combined effect of multiple factors; and 3) the relationships of threshold values with other related factors.展开更多
As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious so...As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious soil and water loss; however, the characteristics of rain splash erosion in those regions are still unclear. The objectives of the study are to ana-lyze the characteristics of splash erosion on loess soil, red soil, purple soil and black soil, and to discuss the relationship between splash erosion and soil properties. Soil samples spatially distributed in the abovementioned regions were col-lected and underwent simulated rainfalls at a high intensity of 1.2mm/min, lasting for 5, 10, 15, and 20min, respectively. Rain splash and soil crust development were analyzed. It shows that black soil sample from Heilongjiang Province corre-sponds to the minimum splash erosion amount because it has high aggregate content, aggregate stability and organic mat-ter content. Loess soil sample from Inner Mongolia corresponds to the maximum splash erosion amount because it has high content of sand particles. Loess soil sample from Shanxi Province has relatively lower splash erosion amount be-cause it has high silt particle content and low aggregate stability easily to be disrupted under rainfalls with high intensity. Although aggregate contents of red soil and purple soil samples from Hubei and Guangdong provinces are high, the sta-bility is weak and prone to be disrupted, so the splash erosion amount is medium. Splash rate which fluctuates over time is observed because soil crust development follows a cycling processes of formation and disruption. In addition, there are two locations of soil crust development, one appears at the surface, and the other occurs at the subsurface.展开更多
It is of great significance to quantify sediment load changing with erosion processes for improving the precision of soil loss prediction. Indoor rainfall experiments were conducted in 2 rainfall intensities(90 mm...It is of great significance to quantify sediment load changing with erosion processes for improving the precision of soil loss prediction. Indoor rainfall experiments were conducted in 2 rainfall intensities(90 mm·h^(-1) and 120 mm·h^(-1)), four slope gradients(17.60%, 26.80%, 36.40%, 46.60%) and 2 slope lengths(5 m, 10 m). Erosion processes are divided into five stages. Results show that sediment yield is mainly sourced from rill erosion, contributing from 54.60% to 95.70% and the duration of which is extended by slope gradients. Sediment load and sediment concentration are significantly different along erosion stages, with the highest values in rill development stage(SIV). Surface flow velocities(interrill and rill) demonstrate less significant differences along erosion stages. Rainfall intensity increases sediment load in all stages, with up to 12.0 times higher when changing from 90 to 120 mm·h^(-1). There is an increasing trend for sediment load and sediment concentration with the rising slope gradient, however, fluctuations existed with the lowest values on 26.80% and 36.40%, respectively, among different treatments. The slope gradient effects are enhanced by rainfall intensity and slope length. Results from this study are important for validating and improving hillslope erosion modelling at each erosion stage.展开更多
In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency...In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency(SRE).The RRE is the ratio of Effect of Runoff Reduction(ERR)by soil and water conservation measure over management degree in a watershed.And The SRE is the ratio of Effect of Sediment Reduction(ESR)by soil and water conservation measure over management degree in a watershed.First of ah,statistical analysis was applied to test the zonal effects of RRE and SRE between different water erosion regions.The results showed that the mean RRE values in northern regions were significantly greater than those of southern regions;and the mean SRE values in northern regions were significantly greater than those in southern regions.Next,the variation of RRE with runoff depth(H)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.Meanwhile,the variation of SRE with specific sediment yield(Y)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.The results showed that RRE had the inverse variation trend as H in both latitude and longitude direction and SRE had the same variation trend as Y in both latitude and longitude direction.Furthermore,the variation of unit management area Runoff Reduction Rate(RRR)with H and RRE was studied in direction of both latitude and longitude.And the variation of unit management area Sediment Reduction Rate(SRR)with Y and SRE was studied in direction of both latitude and longitude.It was found that RRR had the similar variation trend as H in latitude direction and there was critical point around 37°N greater than which RRR began to be equal to H or even larger;RRR had the similar variation trend as H in longitude direction and there was a critical point around 109°E lees than which RRR began to equal to or greater than H;SRR had the similar variation trend as Y in latitude direction and there was critical point around 36°N greater than which SRR began to be equal to Y or even larger;SRR had the similar variation trend as Y in longitude direction and there was a critical point around 106°E lees than which SRR began to equal to or greater than Y.The zonality of RRE,RRR,SRE and SRR was determined by the combined influence of climate variation and special landform in regions controlled by East Asian Monsoon in China.展开更多
基金National Basic Research Program of China, No.2007CB407207Knowledge Innovation Project of Institute of Geographic Sciences and Natural Resources Research,CAS,No.CXIOG-A04-10the support from CAS through its "One Hundred Talent" program
文摘Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on segments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and intensive precipitation, rill can be formed starting even at 15 m from the top of the slope.
基金Under the auspices of National Natural Science Foundation of China(No. 40971165,41001165)Open Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau(No. K318009902-1315)
文摘Rills are frequently observed on slope farmlands and rill erosion significantly contributes to sediment yields. This paper focuses on reviewing the various factors affecting rill erosion processes and the threshold conditions of rill initiation. Six factors, including rainfall, runoff, soil, topography, vegetation and tillage system, are discussed. Rill initiation and network are explored. Runoff erosivity and soil erodibility are recognized as two direct factors affecting rill erosion and other types of factors may have indirect influences on rill erosion through increasing or decreasing the effects of the direct factors. Certain conditions are necessary for rill initiation and the critical conditions are different with different factors. Future studies should be focused on 1) the dynamic changes of rill networks; 2) the combined effect of multiple factors; and 3) the relationships of threshold values with other related factors.
基金Under the auspices of National Natural Science Foundation of China ( No. 40471084)Innovation Program of Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (No. 066U0104SZ)State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau (No. 10501-173)
文摘As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious soil and water loss; however, the characteristics of rain splash erosion in those regions are still unclear. The objectives of the study are to ana-lyze the characteristics of splash erosion on loess soil, red soil, purple soil and black soil, and to discuss the relationship between splash erosion and soil properties. Soil samples spatially distributed in the abovementioned regions were col-lected and underwent simulated rainfalls at a high intensity of 1.2mm/min, lasting for 5, 10, 15, and 20min, respectively. Rain splash and soil crust development were analyzed. It shows that black soil sample from Heilongjiang Province corre-sponds to the minimum splash erosion amount because it has high aggregate content, aggregate stability and organic mat-ter content. Loess soil sample from Inner Mongolia corresponds to the maximum splash erosion amount because it has high content of sand particles. Loess soil sample from Shanxi Province has relatively lower splash erosion amount be-cause it has high silt particle content and low aggregate stability easily to be disrupted under rainfalls with high intensity. Although aggregate contents of red soil and purple soil samples from Hubei and Guangdong provinces are high, the sta-bility is weak and prone to be disrupted, so the splash erosion amount is medium. Splash rate which fluctuates over time is observed because soil crust development follows a cycling processes of formation and disruption. In addition, there are two locations of soil crust development, one appears at the surface, and the other occurs at the subsurface.
基金National Natural Science Foundation of China,No.41471229The Open Project Fund from the State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau,No.A314021402-1601National Key Research and Development Program of China,No.2016YFA0601900
文摘It is of great significance to quantify sediment load changing with erosion processes for improving the precision of soil loss prediction. Indoor rainfall experiments were conducted in 2 rainfall intensities(90 mm·h^(-1) and 120 mm·h^(-1)), four slope gradients(17.60%, 26.80%, 36.40%, 46.60%) and 2 slope lengths(5 m, 10 m). Erosion processes are divided into five stages. Results show that sediment yield is mainly sourced from rill erosion, contributing from 54.60% to 95.70% and the duration of which is extended by slope gradients. Sediment load and sediment concentration are significantly different along erosion stages, with the highest values in rill development stage(SIV). Surface flow velocities(interrill and rill) demonstrate less significant differences along erosion stages. Rainfall intensity increases sediment load in all stages, with up to 12.0 times higher when changing from 90 to 120 mm·h^(-1). There is an increasing trend for sediment load and sediment concentration with the rising slope gradient, however, fluctuations existed with the lowest values on 26.80% and 36.40%, respectively, among different treatments. The slope gradient effects are enhanced by rainfall intensity and slope length. Results from this study are important for validating and improving hillslope erosion modelling at each erosion stage.
基金Financial support was provided by the National Natural Science Foundation of China(Grant No.41271304,Grant No.41001165)Open Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on Loees Plateau(K318009902-1315).
文摘In this particular study,99 typical managed small watersheds which representing five water erosion areas in China were selected to study zonality of Runoff Reduction Efficiency(RRE)and of Sediment Reduction Efficiency(SRE).The RRE is the ratio of Effect of Runoff Reduction(ERR)by soil and water conservation measure over management degree in a watershed.And The SRE is the ratio of Effect of Sediment Reduction(ESR)by soil and water conservation measure over management degree in a watershed.First of ah,statistical analysis was applied to test the zonal effects of RRE and SRE between different water erosion regions.The results showed that the mean RRE values in northern regions were significantly greater than those of southern regions;and the mean SRE values in northern regions were significantly greater than those in southern regions.Next,the variation of RRE with runoff depth(H)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.Meanwhile,the variation of SRE with specific sediment yield(Y)was studied in direction of both latitude and longitude across regions influenced by East Asian Monsoon.The results showed that RRE had the inverse variation trend as H in both latitude and longitude direction and SRE had the same variation trend as Y in both latitude and longitude direction.Furthermore,the variation of unit management area Runoff Reduction Rate(RRR)with H and RRE was studied in direction of both latitude and longitude.And the variation of unit management area Sediment Reduction Rate(SRR)with Y and SRE was studied in direction of both latitude and longitude.It was found that RRR had the similar variation trend as H in latitude direction and there was critical point around 37°N greater than which RRR began to be equal to H or even larger;RRR had the similar variation trend as H in longitude direction and there was a critical point around 109°E lees than which RRR began to equal to or greater than H;SRR had the similar variation trend as Y in latitude direction and there was critical point around 36°N greater than which SRR began to be equal to Y or even larger;SRR had the similar variation trend as Y in longitude direction and there was a critical point around 106°E lees than which SRR began to equal to or greater than Y.The zonality of RRE,RRR,SRE and SRR was determined by the combined influence of climate variation and special landform in regions controlled by East Asian Monsoon in China.
