Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical...Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis)in semiarid areas as subject,this study quantified the effects of canopies and roots on controlling slope runoff and erosion.A series of field experiments were conducted in a loess hilly region of China.Field plots(5 m length,2 m width,25°slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass;only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h^(-1))and upslope inflow(10,30,50,70,90L min^(-1)).The results showed that compared with bare soil,intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average,and decreased soil erodibility parameter by 66.3%.As inflow rate increased,the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min^(-1)and 35.11 to 121.96 g m^(-2)min^(-1),respectively.Canopies relatively contributed 66.7% to lowering flow velocity,turbulence,weakening erosive force and increasing hydraulic resistance.Roots played a predominant role in reducing soil loss and enhancing soil antierodibility,with relative contributions of 78.8% and 73.8%.Furthermore,the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most.These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections.We suggest protecting Coreopsis with intact grass at upper slope sections,while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections,with roots reserved.展开更多
Comprehensive assessments of ecosystem services in environments under the influences of human activities and climate change are critical for sustainable regional ecosystem management. Therefore,integrated interdiscipl...Comprehensive assessments of ecosystem services in environments under the influences of human activities and climate change are critical for sustainable regional ecosystem management. Therefore,integrated interdisciplinary modelling has become a major focus of ecosystem service assessment. In this study, we established a model that integrates land use/cover change(LUCC), climate change, and water retention services to evaluate the spatial and temporal variations of water retention services in the Loess Plateau of China in the historical period(2000–2015) and in the future(2020–2050). An improved Markov-Cellular Automata(Markov-CA) model was used to simulate land use/land cover patterns, and ArcGIS 10.2 software was used to simulate and assess water retention services from 2000 to 2050 under six combined scenarios, including three land use/land cover scenarios(historical scenario(HS), ecological protection scenario(EPS), and urban expansion scenario(UES)) and two climate change scenarios(RCP4.5 and RCP8.5, where RCP is the representative concentration pathway). LUCCs in the historical period(2000–2015) and in the future(2020–2050) are dominated by transformations among agricultural land, urban land and grassland. Urban land under UES increased significantly by 0.63×10^(3) km^(2)/a, which was higher than the increase of urban land under HS and EPS. In the Loess Plateau, water yield decreased by 17.20×10^(6) mm and water retention increased by 0.09×10^(6) mm in the historical period(2000–2015),especially in the Interior drainage zone and its surrounding areas. In the future(2020–2050), the pixel means of water yield is higher under RCP4.5 scenario(96.63 mm) than under RCP8.5 scenario(95.46mm), and the pixel means of water retention is higher under RCP4.5 scenario(1.95 mm) than under RCP8.5 scenario(1.38 mm). RCP4.5-EPS shows the highest total water retention capacity on the plateau scale among the six combined scenarios, with the value of 1.27×10^(6) mm. Ecological restoration projects in the Loess Plateau have enhanced soil and water retention. However, more attention needs to be paid not only to the simultaneous increase in water retention services and evapotranspiration but also to the type and layout of restored vegetation. Furthermore, urbanization needs to be controlled to prevent uncontrollable LUCCs and climate change. Our findings provide reference data for the regional water and land resources management and the sustainable development of socio-ecological systems in the Loess Plateau under LUCC and climate change scenarios.展开更多
In this paper,the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments,considering the wind speed,blown angle of wind and soil moisture c...In this paper,the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments,considering the wind speed,blown angle of wind and soil moisture content.The results showed that the modulus of soil wind erosion increases with an increase of wind speed.When the wind speed exceeds a critical value,the soil wind erosion suddenly increases.The critical speed for both kinds of soil is within the range of 7-8m·s-1.For a constant wind speed,the rate of soil wind erosion changes from increasing to falling at a critical soil slope.The critical slope of loam soil and sandy loam soil is 20° and 10°,respectively.Soil moisture content has a significant effect on wind erosion.Soil wind erosion of both soils decreases with an increase of the soil water content in two treatments,however,for treatment two,the increasing trends of wind erosion for two soils with the falling of soil water content are no significant,especially for the loam soil,and in the same soil water content,the wind erosion of two soils in treatment one is significantly higher than treatment two,this indicates reducing the disturbance of soil surface can evidently control the soil wind erosion.展开更多
Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau.Based on the data of check-dams from 1950 to 2014,our study roundly analyzed the ...Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau.Based on the data of check-dams from 1950 to 2014,our study roundly analyzed the regional distribution,function and the problems of check-dams on the Loess Plateau.A total of 17,094 check-dams with a storage capacity of over 100,000 m^(3) and an average density of 0.027 counts km^(-2) were installed on the Loess Plateau.Check-dams’densities varied greatly in the Qinghai Province,Gansu Province,Ningxia Hui Autonomous Region,Inner Mongolia Autonomous Region,Shaanxi Province,Shanxi Province and Henan Province.The highest density of check-dams reached 0.088 counts km^(-2) in Shaanxi Province,whereas the lowest density of check-dams was only 0.005 counts km^(-2) in Qinghai Province.However,after decades of operation,3025 large check-dams and 2257 medium check dams are dangerous and have security risks,which are seriously threatening downstream safety.The dangerous rate of checkdams is high.Specifically,the check-dams in Shanxi and Qinghai Province have the highest dangerous rates,with both exceeding 53%.Therefore,there is an urgent need for carrying out reinforcement of the dangerous check-dams.The results are helpful to policymakers to extend and develop check-dams.展开更多
The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mecha...The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning's roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning's roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.展开更多
Crop residue is a major source of soil organic matter;therefore,application of crop straw to soil contributes to the sustainable development of organic agriculture.To better understand the transformation of crop straw...Crop residue is a major source of soil organic matter;therefore,application of crop straw to soil contributes to the sustainable development of organic agriculture.To better understand the transformation of crop straw in orchard soils,we investigated the relationship between the characteristics of straw decomposition and functional diversity of associated microbial communities in a long-term peach orchard,China.Mesh bags,each containing 30 g of corn or bean straw,were buried at a soil depth of 20 cm in a 12-year-old peach orchard for 360 d(October 2011–October 2012).Three treatments were applied,i.e.,fresh corn straw,fresh corn straw with nitrogen fertilizer(urea,10.34 g/kg),and fresh bean straw.Changes in straw residual rate,straw water content and soil conditions were monitored after treatment.The functional diversity of straw-associated microbial communities was analyzed by the Biolog-Eco microplate assay.During the decomposition process,straw residual rates did not vary considerably from 10 d(30.4%–45.4%)to 360 d(19.0%–30.3%).Irrespective of nitrogen addition,corn straw decomposed faster than bean straw.Corn straw with nitrogen fertilizer yielded the highest average well color development(AWCD)values(1.11–1.67),followed by corn straw(1.14–1.68)and bean straw(1.18–1.62).Although the AWCD values did not differ significantly among the three treatments,substantial differences occurred across various time periods of the decomposition process(P<0.01).In terms of carbon source utilization,the dominant microbial groups fed mainly on saccharides.Hard-to-decompose substances gradually accumulated in the middle and late stages of straw decomposition.Of the six categories of carbon sources tested,the utilization rate of aromatics was the lowest with corn straw,whereas that of polymers was the lowest with bean straw.Among different treatments,straw residual rate was negatively correlated to soil available phosphorous,soil available potassium and soil temperature(P<0.05),but not to soil water content.In some cases(corn straw with or without nitrogen fertilizer),straw residual rate was negatively correlated to straw water content,amino acid utilization and carboxylic acid utilization,and positively correlated with microbial species richness and evenness(P<0.05).Microbial community associated with corn and bean straw decomposition in soil was respectively dominated by aromatic-and polymer-metabolizing groups during the middle and late stages of this process,which could reduce the stability of microbial community structure and decrease the rate of straw decomposition in the fruit tree orchard.展开更多
Yulin is a typical ecological fragile area in China, and its vegetation ecosystem is so fragile that could be vulnerable to climate change and human activities. Spatial and temporal change of vegetation Normalized Dif...Yulin is a typical ecological fragile area in China, and its vegetation ecosystem is so fragile that could be vulnerable to climate change and human activities. Spatial and temporal change of vegetation Normalized Difference Vegetation Index (NDVI) and its relationship with climate change and human activities were analyzed based on MODIS NDVI data from 2000 to 2015, as well as annual temperature and precipitation data from 2000 to 2014, and linear trend analysis, correlation and buffer analysis were used. Result showed: 1) NDVI value was small and vegetation cover was low, but NDVI had a linear growth rate of 0.0096/annum from 2000 to 2015 in Yulin area. The area of growth trend accounted for 97.06% of the total area, while the area with decreased rate was small, which mainly had correlation with human activities, and was distributed in the southwest mountain area, urban neighborhood, and river valley in the middle and east of Yulin area. 2) Correlation analysis between NDVI and temperature, precipitation, respectively, reflected that negative correlation was between NDVI and temperature, while positive correlation was between NDVI and precipitation. Furthermore, the role of precipitation was higher than that of temperature in the process of interaction between NDVI and temperature, precipitation. 3) NDVI change process in the range of human activities indicated that the intensity of human activities in buffer_city area was higher than that in buffer_county area. Buffer_city area was divided into within 5 km area with dramatic impact by human activities, and from 5 km to 9 km area with less impact by human activities, and outside 9 km area with mini-affected by human activities.展开更多
The effect of mulching with straw, white plastic film and black plastic film for improving soil water storage and on the soil properties was examined in a wheat-maize rotation system on Loess soil in northwestern Chin...The effect of mulching with straw, white plastic film and black plastic film for improving soil water storage and on the soil properties was examined in a wheat-maize rotation system on Loess soil in northwestern China. All the mulches improved the water storage to some extent and led to warmer soils. However, the organic C and total N contents of the soils declined significantly under the mulches, particularly the plastic film mulches,and this could have long-term detrimental effects on soil quality and the sustainability of the some mulching practices.展开更多
Crop production vulnerability to climate change in Northwest China depends upon multiple socio-ecological factors.Knowledge regarding the specific indicators and methods suitable for assessing crop production vulnerab...Crop production vulnerability to climate change in Northwest China depends upon multiple socio-ecological factors.Knowledge regarding the specific indicators and methods suitable for assessing crop production vulnerability is limited that address spatiotemporal variations across large and diverse zones.We propose an integrated assessment framework to quantify the vulnerability of crop production derived from crop yield sensitivity,exposure,and adaptive consequences across 338 counties in Northwest China during 1995–2014.Maps on these indices were generated using climatic and socioeconomic data with spatial mapping method.Different clusters of crop production vulnerability were then identified by a k-means cluster method to assess the heterogeneity of vulnerability at a regional scale.Results show that the vulnerability of crop production in 338 counties varies significantly in both geographical and socioeconomic aspects,specifically,vulnerability indicators are generally higher in Minhe,Menyuan,Hualong,and Ledu,and Xayar had the lowest value of vulnerability.This indicates that adaptation strategies for regional crop production need to focus on several levels,from the improvement of adaptive ability to crop yield fluctuation by promoting irrigation agriculture and optimizing limited water resources in typical arid areas,to agriculture-related financial policies incentivizing the capital investment and technology upgrade of crop production on traditional farming regions.This study provides convincing evidence that the factors related to socioeconomic policies are particularly alarming when a crop’s risk is compared to precipitation fluctuations.We recommend these findings be used to facilitate regional agriculture planning to reduce crop production vulnerability and ensure sustainable food security in specific regions.展开更多
The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China,that forms an important divide between landforms and biogeographic regions.The populated part of the Liupan Mountain Region has s...The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China,that forms an important divide between landforms and biogeographic regions.The populated part of the Liupan Mountain Region has suffered tremendous ecological damage over time due to population pressure,excessive demand and inappropriate use of agricultural land resources.To present the relationship between land use/cover change and spatio-temporal variation of soil erosion,data sets of land use between the late 1980s and 2000 were obtained from Landsat Thematic Mapper(TM)imagery,and spatial models were used to characterize landscape and soil erosion conditions.Also,soil erosion in response to land use and land cover change were quantified and analyzed using data from geographical information systems and remote sensing.Soil erosion by water was the dominant mode of soil loss,while soil erosion by wind was only present on a relatively small area.The degree of soil erosion was classified into five severity classes:slight,light,moderate,severe,and very severe.Soil erosion in the Liupan Mountain Region increased between the late 1980s and 2000,both in terms of acreage and severity.Moderate,severe,and very severe eroded areas accounted for 54.86%of the total land area.The lightly eroded area decreased,while the moderately eroded area increased by 368817 ha(22%)followed by severe erosion with 146552 ha(8.8%),and very severe erosion by 97067.6 ha(5.8%).Soil loss on sloping cropland increased with slope gradients.About 90%of the cropland was located on slopes less than 15°.Most of the increase in soil erosion on cropland was due to conversion of steep slopes to cropland and degradation of grassland and increased activities.Soil erosion was severe on grassland with a moderate or low grass cover and on dry land.Human activities,cultivation on steep slopes,and overgrazing of pastures were the main reasons for the increase in erosion severity.展开更多
The Revised Universal Soil Loss Equation(RUSLE)is widely used to estimate regional soil erosion.However,quantitative impacts of soil and water conservation(SWC)measures on conservation practice factor(P)of the RUSLE r...The Revised Universal Soil Loss Equation(RUSLE)is widely used to estimate regional soil erosion.However,quantitative impacts of soil and water conservation(SWC)measures on conservation practice factor(P)of the RUSLE remain largely unclear,especially for the mountainous and hilly areas.In this study,we improved the RUSLE by considering quantitative impacts of different SWC measures on the P factor value.The improved RUSLE was validated against the long-term(2000-2015)soil erosion monitoring data obtained from 96 runoff plots(15—35°)in mountainous and hilly areas of Hubei Province,China;the result presented a high accuracy with the determination coefficient of 0.89.Based on the erosion monitoring data of 2018 and 2019,the Root Mean Square Error of the result by the improved RUSLE was 28.0%smaller than that by the original RUSLE with decrement of 19.6%—24.0%in the average P factor values,indicating that the soil erosion modelling accuracy was significantly enhanced by the improved RUSLE.Relatively low P factor values appeared for farmlands with tillage measures(P<0.53),grasslands with engineering measures(P<0.23),woodlands with biological measures(P<0.28),and other land use types with biological measures(P<0.51).The soil erosion modulus showed a downward trend with the corresponding values of 1681.21,1673.14,1594.70,1482.40 and 1437.50 t km^(-2)a-1 in 2000,2005,2010,2015 and 2019,respectively.The applicability of the improved RUSLE was verified by the measurements in typical mountainous and hilly areas of Hubei Province,China,and arrangements of SWC measures of this area were proposed.展开更多
Landscape alterations and ecosystem services(ES)are crucial elements that affect the socioecological development of ecologically fragile regions.To provide scientific support for the land-use planning and regional eco...Landscape alterations and ecosystem services(ES)are crucial elements that affect the socioecological development of ecologically fragile regions.To provide scientific support for the land-use planning and regional ecological restoration to achieve sustainable development goals(SDGs)in the Loess Plateau from 1992 to 2015,this study proposes an integrated assessment framework for assessing the supply-demand match and equilibrium of ES combining potential relationships between landscape alterations,ES,and sustainable development at the county and regional scales.Results show that more than 85%of local counties have a supply-demand mismatch in terms of ecosystem services.Supply-demand distributions for provisioning and supporting services were relatively balanced compared to cultural services,which were imbalanced.Although the overall supply-demand relationship is relatively balanced because of the significant influence of ecological restoration,it shows an increasing trend toward imbalance as human-land conflict is prominent in some regions.SDGs emphasize on specific ES information such as ecosystem conservation,sustainable agriculture,and urban construction.Furtherly,positive impacts from landscape dynamics can improve the supply capacity of the ES and contribute to regional sustainability.展开更多
Rare earth element(REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different REE on different soil depth across a slope in an indoor plot, two simulated rainfalls ...Rare earth element(REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different REE on different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amount increases with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4.3 and 5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amount. The new REE tracer method should be useful to future studying of erosion processes on slope lands.展开更多
Evaluating the effects of revegetation on runoff and erosion reduction is essential for studying soil and water conservation on the Loess Plateau after implementation of China's Grain for Green Project.However,qua...Evaluating the effects of revegetation on runoff and erosion reduction is essential for studying soil and water conservation on the Loess Plateau after implementation of China's Grain for Green Project.However,quantifying the influence of revegetation on the erosion caused by concentrated runoff in extreme rainstorms is still challenging.To evaluate this influence,scouring-erosion experiments were implemented in situ on the vegetated hillslope plots(GR)and bare hillslope plots(CK).The runoffreducing effects of grass(GRR)averaged 31%,20%and 8%,and the erosion-reducing effects of grass(GER)averaged 93%,95%and 93%on the 5-plots,10-plots and 18-plots,respectively.The ratios of GRR to GER were 0.09e0.33,implying that the ability of vegetation to reduce erosion was greater than its ability to reduce runoff.The GRR and GER obviously decreased as the inflow rate increased,and the GRR decreased as the hillslope gradient increased,but there were no obvious differences in the GER between hillslope gradients.Vegetation could decrease the ability of the concentrated flow to carry and transport sediment and increase the energy consumption of the concentrated flow in response to hydraulic resistance.Vegetation also significantly reduced the degree of rill development.The degree of rill dissection on the GR(0.054e0.087 m^(2)m^(2))was lower than that on the CK(0.061e0.184 m^(2)m^(2)).Our findings provide an essential reference for ecological environment and vegetation restoration on loess hillslopes.展开更多
The loessal hill region in southern Ningxia is a semiarid and severe eroded area with developed agriculture and animal husbandry. It has long been an argument whether there might be more potentiality of farming and wh...The loessal hill region in southern Ningxia is a semiarid and severe eroded area with developed agriculture and animal husbandry. It has long been an argument whether there might be more potentiality of farming and whether food production can be sustained at a level of local sufficiency.展开更多
Hydrodynamic dispersion is a measure for describing the process of solute transport in porous media.Characterizing the dispersion of water flow within gravel is essential for the prediction of solute transport especia...Hydrodynamic dispersion is a measure for describing the process of solute transport in porous media.Characterizing the dispersion of water flow within gravel is essential for the prediction of solute transport especially nonpoint source pollutants migration in alpine watersheds where the land surface is typically covered with gravel.In this study,an integrated model and experimental method using an electrolyte tracer is proposed for determination of the hydrodynamic dispersion coefficient.Two experimental scenarios were designed to measure electrolyte tracer transport processes in both free water flow and gravel layer flow under different slope gradients and transport distances.Subsequently,the measured data were used to simultaneously calculate both the hydrodynamic dispersion coefficient and flow velocity by fitting the experimental data with the mathematical model.Dispersivity,as a critical feature of hydrodynamic dispersion,was determined as well under the two specified scenarios.Finally,the impact mechanisms of the gravel layer and factors related to the dispersion processes were comprehensively analyzed.The results indicate that the presence of a gravel layer significantly reduces flow velocity and the hydrodynamic dispersion coefficient,but increases solute dispersivity.For the flow within gravel layers,with much lower velocity,the positive effect of the gravel layer on dispersivity may be neutralized or even surpassed by the negative effect of flow velocity.The results should be helpful in characterizing the dispersion processes of water flow within gravel layer and hence in predicting solute transport,especially in nonpoint source pollutants migration in alpine watersheds where the land surface is richly covered with gravel.展开更多
基金supported by the National Natural Science Foundation of China(41907061)the Natural Science Foundation of Hubei province,China(2021CFB550)the joint fund for regional innovation and development of NSFC(U21A2039)。
文摘Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis)in semiarid areas as subject,this study quantified the effects of canopies and roots on controlling slope runoff and erosion.A series of field experiments were conducted in a loess hilly region of China.Field plots(5 m length,2 m width,25°slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass;only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h^(-1))and upslope inflow(10,30,50,70,90L min^(-1)).The results showed that compared with bare soil,intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average,and decreased soil erodibility parameter by 66.3%.As inflow rate increased,the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min^(-1)and 35.11 to 121.96 g m^(-2)min^(-1),respectively.Canopies relatively contributed 66.7% to lowering flow velocity,turbulence,weakening erosive force and increasing hydraulic resistance.Roots played a predominant role in reducing soil loss and enhancing soil antierodibility,with relative contributions of 78.8% and 73.8%.Furthermore,the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most.These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections.We suggest protecting Coreopsis with intact grass at upper slope sections,while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections,with roots reserved.
基金supported by the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(A314021402–202110)the Science Foundation of Hubei Province,China(2021CFB295)the National Natural Science Foundation of China(42077451)。
文摘Comprehensive assessments of ecosystem services in environments under the influences of human activities and climate change are critical for sustainable regional ecosystem management. Therefore,integrated interdisciplinary modelling has become a major focus of ecosystem service assessment. In this study, we established a model that integrates land use/cover change(LUCC), climate change, and water retention services to evaluate the spatial and temporal variations of water retention services in the Loess Plateau of China in the historical period(2000–2015) and in the future(2020–2050). An improved Markov-Cellular Automata(Markov-CA) model was used to simulate land use/land cover patterns, and ArcGIS 10.2 software was used to simulate and assess water retention services from 2000 to 2050 under six combined scenarios, including three land use/land cover scenarios(historical scenario(HS), ecological protection scenario(EPS), and urban expansion scenario(UES)) and two climate change scenarios(RCP4.5 and RCP8.5, where RCP is the representative concentration pathway). LUCCs in the historical period(2000–2015) and in the future(2020–2050) are dominated by transformations among agricultural land, urban land and grassland. Urban land under UES increased significantly by 0.63×10^(3) km^(2)/a, which was higher than the increase of urban land under HS and EPS. In the Loess Plateau, water yield decreased by 17.20×10^(6) mm and water retention increased by 0.09×10^(6) mm in the historical period(2000–2015),especially in the Interior drainage zone and its surrounding areas. In the future(2020–2050), the pixel means of water yield is higher under RCP4.5 scenario(96.63 mm) than under RCP8.5 scenario(95.46mm), and the pixel means of water retention is higher under RCP4.5 scenario(1.95 mm) than under RCP8.5 scenario(1.38 mm). RCP4.5-EPS shows the highest total water retention capacity on the plateau scale among the six combined scenarios, with the value of 1.27×10^(6) mm. Ecological restoration projects in the Loess Plateau have enhanced soil and water retention. However, more attention needs to be paid not only to the simultaneous increase in water retention services and evapotranspiration but also to the type and layout of restored vegetation. Furthermore, urbanization needs to be controlled to prevent uncontrollable LUCCs and climate change. Our findings provide reference data for the regional water and land resources management and the sustainable development of socio-ecological systems in the Loess Plateau under LUCC and climate change scenarios.
基金supported by Key Program of National Natural Science Foundation of China(Grant No. 41130744)China National Natural Science Foundation (Grant No. 40971165)State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau open Foundation(Grant No. 10501-1220)
文摘In this paper,the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments,considering the wind speed,blown angle of wind and soil moisture content.The results showed that the modulus of soil wind erosion increases with an increase of wind speed.When the wind speed exceeds a critical value,the soil wind erosion suddenly increases.The critical speed for both kinds of soil is within the range of 7-8m·s-1.For a constant wind speed,the rate of soil wind erosion changes from increasing to falling at a critical soil slope.The critical slope of loam soil and sandy loam soil is 20° and 10°,respectively.Soil moisture content has a significant effect on wind erosion.Soil wind erosion of both soils decreases with an increase of the soil water content in two treatments,however,for treatment two,the increasing trends of wind erosion for two soils with the falling of soil water content are no significant,especially for the loam soil,and in the same soil water content,the wind erosion of two soils in treatment one is significantly higher than treatment two,this indicates reducing the disturbance of soil surface can evidently control the soil wind erosion.
基金supported by the Open Research Program of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(SKLGP2020K009)the Open Research Program of the Key Laboratory of Mountain Hazards and Earth Surface Processes,Chinese Academy of Sciences(KLMHESP-20-03)the CRSRI Open Research Program(CKWV2019762/KY)。
文摘Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau.Based on the data of check-dams from 1950 to 2014,our study roundly analyzed the regional distribution,function and the problems of check-dams on the Loess Plateau.A total of 17,094 check-dams with a storage capacity of over 100,000 m^(3) and an average density of 0.027 counts km^(-2) were installed on the Loess Plateau.Check-dams’densities varied greatly in the Qinghai Province,Gansu Province,Ningxia Hui Autonomous Region,Inner Mongolia Autonomous Region,Shaanxi Province,Shanxi Province and Henan Province.The highest density of check-dams reached 0.088 counts km^(-2) in Shaanxi Province,whereas the lowest density of check-dams was only 0.005 counts km^(-2) in Qinghai Province.However,after decades of operation,3025 large check-dams and 2257 medium check dams are dangerous and have security risks,which are seriously threatening downstream safety.The dangerous rate of checkdams is high.Specifically,the check-dams in Shanxi and Qinghai Province have the highest dangerous rates,with both exceeding 53%.Therefore,there is an urgent need for carrying out reinforcement of the dangerous check-dams.The results are helpful to policymakers to extend and develop check-dams.
基金supported by the National Natural Science Foundation of China(Grant No40901138)the Project of the State Key Laboratory of Earth Surface Processes and Resource Ecology(Grant No 2008-KF-05)the Project of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(Grant No10501-283)
文摘The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning's roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning's roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.
基金the Project of State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau,Chinese Academy of Sciences(A314021402-1916)the Key Project of the Ministry of Science and Technology of China(2017YFD0200200)the Innovative Engineering Project of Shaanxi Province,China(2016slkj-15)。
文摘Crop residue is a major source of soil organic matter;therefore,application of crop straw to soil contributes to the sustainable development of organic agriculture.To better understand the transformation of crop straw in orchard soils,we investigated the relationship between the characteristics of straw decomposition and functional diversity of associated microbial communities in a long-term peach orchard,China.Mesh bags,each containing 30 g of corn or bean straw,were buried at a soil depth of 20 cm in a 12-year-old peach orchard for 360 d(October 2011–October 2012).Three treatments were applied,i.e.,fresh corn straw,fresh corn straw with nitrogen fertilizer(urea,10.34 g/kg),and fresh bean straw.Changes in straw residual rate,straw water content and soil conditions were monitored after treatment.The functional diversity of straw-associated microbial communities was analyzed by the Biolog-Eco microplate assay.During the decomposition process,straw residual rates did not vary considerably from 10 d(30.4%–45.4%)to 360 d(19.0%–30.3%).Irrespective of nitrogen addition,corn straw decomposed faster than bean straw.Corn straw with nitrogen fertilizer yielded the highest average well color development(AWCD)values(1.11–1.67),followed by corn straw(1.14–1.68)and bean straw(1.18–1.62).Although the AWCD values did not differ significantly among the three treatments,substantial differences occurred across various time periods of the decomposition process(P<0.01).In terms of carbon source utilization,the dominant microbial groups fed mainly on saccharides.Hard-to-decompose substances gradually accumulated in the middle and late stages of straw decomposition.Of the six categories of carbon sources tested,the utilization rate of aromatics was the lowest with corn straw,whereas that of polymers was the lowest with bean straw.Among different treatments,straw residual rate was negatively correlated to soil available phosphorous,soil available potassium and soil temperature(P<0.05),but not to soil water content.In some cases(corn straw with or without nitrogen fertilizer),straw residual rate was negatively correlated to straw water content,amino acid utilization and carboxylic acid utilization,and positively correlated with microbial species richness and evenness(P<0.05).Microbial community associated with corn and bean straw decomposition in soil was respectively dominated by aromatic-and polymer-metabolizing groups during the middle and late stages of this process,which could reduce the stability of microbial community structure and decrease the rate of straw decomposition in the fruit tree orchard.
文摘Yulin is a typical ecological fragile area in China, and its vegetation ecosystem is so fragile that could be vulnerable to climate change and human activities. Spatial and temporal change of vegetation Normalized Difference Vegetation Index (NDVI) and its relationship with climate change and human activities were analyzed based on MODIS NDVI data from 2000 to 2015, as well as annual temperature and precipitation data from 2000 to 2014, and linear trend analysis, correlation and buffer analysis were used. Result showed: 1) NDVI value was small and vegetation cover was low, but NDVI had a linear growth rate of 0.0096/annum from 2000 to 2015 in Yulin area. The area of growth trend accounted for 97.06% of the total area, while the area with decreased rate was small, which mainly had correlation with human activities, and was distributed in the southwest mountain area, urban neighborhood, and river valley in the middle and east of Yulin area. 2) Correlation analysis between NDVI and temperature, precipitation, respectively, reflected that negative correlation was between NDVI and temperature, while positive correlation was between NDVI and precipitation. Furthermore, the role of precipitation was higher than that of temperature in the process of interaction between NDVI and temperature, precipitation. 3) NDVI change process in the range of human activities indicated that the intensity of human activities in buffer_city area was higher than that in buffer_county area. Buffer_city area was divided into within 5 km area with dramatic impact by human activities, and from 5 km to 9 km area with less impact by human activities, and outside 9 km area with mini-affected by human activities.
基金supported by the National High-tech R&D Program of China (2013AA102904, 2011AA100503)the Sci-tech Coordination and Innovation Project of Shaanxi Province (2016KTZDNY03-06)+1 种基金Chinese "111" Project (B12007)supported by the Chinese Scholarship Council at Royal Agricultural University, UK
文摘The effect of mulching with straw, white plastic film and black plastic film for improving soil water storage and on the soil properties was examined in a wheat-maize rotation system on Loess soil in northwestern China. All the mulches improved the water storage to some extent and led to warmer soils. However, the organic C and total N contents of the soils declined significantly under the mulches, particularly the plastic film mulches,and this could have long-term detrimental effects on soil quality and the sustainability of the some mulching practices.
基金funded by the National Natural Science Foundation of China(41601184)the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(A314021402-202110)。
文摘Crop production vulnerability to climate change in Northwest China depends upon multiple socio-ecological factors.Knowledge regarding the specific indicators and methods suitable for assessing crop production vulnerability is limited that address spatiotemporal variations across large and diverse zones.We propose an integrated assessment framework to quantify the vulnerability of crop production derived from crop yield sensitivity,exposure,and adaptive consequences across 338 counties in Northwest China during 1995–2014.Maps on these indices were generated using climatic and socioeconomic data with spatial mapping method.Different clusters of crop production vulnerability were then identified by a k-means cluster method to assess the heterogeneity of vulnerability at a regional scale.Results show that the vulnerability of crop production in 338 counties varies significantly in both geographical and socioeconomic aspects,specifically,vulnerability indicators are generally higher in Minhe,Menyuan,Hualong,and Ledu,and Xayar had the lowest value of vulnerability.This indicates that adaptation strategies for regional crop production need to focus on several levels,from the improvement of adaptive ability to crop yield fluctuation by promoting irrigation agriculture and optimizing limited water resources in typical arid areas,to agriculture-related financial policies incentivizing the capital investment and technology upgrade of crop production on traditional farming regions.This study provides convincing evidence that the factors related to socioeconomic policies are particularly alarming when a crop’s risk is compared to precipitation fluctuations.We recommend these findings be used to facilitate regional agriculture planning to reduce crop production vulnerability and ensure sustainable food security in specific regions.
基金This research was supported by program of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Water and Soil Conservation,Chinese Academy of Sciences and Ministry of Water Resources(No.10501-298)National Key Basic Research Program(2007CB407200)Open Research Fund of State Key Laboratory of Remote Sensing Science,Jointly Sponsored by Beijing Normal University and the Institude of Remote Sensing Applicantions of Chinese Academy of Sciences(2009KFJJ019).
文摘The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China,that forms an important divide between landforms and biogeographic regions.The populated part of the Liupan Mountain Region has suffered tremendous ecological damage over time due to population pressure,excessive demand and inappropriate use of agricultural land resources.To present the relationship between land use/cover change and spatio-temporal variation of soil erosion,data sets of land use between the late 1980s and 2000 were obtained from Landsat Thematic Mapper(TM)imagery,and spatial models were used to characterize landscape and soil erosion conditions.Also,soil erosion in response to land use and land cover change were quantified and analyzed using data from geographical information systems and remote sensing.Soil erosion by water was the dominant mode of soil loss,while soil erosion by wind was only present on a relatively small area.The degree of soil erosion was classified into five severity classes:slight,light,moderate,severe,and very severe.Soil erosion in the Liupan Mountain Region increased between the late 1980s and 2000,both in terms of acreage and severity.Moderate,severe,and very severe eroded areas accounted for 54.86%of the total land area.The lightly eroded area decreased,while the moderately eroded area increased by 368817 ha(22%)followed by severe erosion with 146552 ha(8.8%),and very severe erosion by 97067.6 ha(5.8%).Soil loss on sloping cropland increased with slope gradients.About 90%of the cropland was located on slopes less than 15°.Most of the increase in soil erosion on cropland was due to conversion of steep slopes to cropland and degradation of grassland and increased activities.Soil erosion was severe on grassland with a moderate or low grass cover and on dry land.Human activities,cultivation on steep slopes,and overgrazing of pastures were the main reasons for the increase in erosion severity.
基金funded by the Natural Science Foundation of China Project(41907061)the National Key Research and Development Program(2016YFC0503506)+1 种基金the Research Program from the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(A314021402-2005)the Research Center on Mountain Torrent&Geologic Disaster Prevention of the Ministry of Water Resources,Changjiang River Scientific Research Institute(CKWV2019761/KY).
文摘The Revised Universal Soil Loss Equation(RUSLE)is widely used to estimate regional soil erosion.However,quantitative impacts of soil and water conservation(SWC)measures on conservation practice factor(P)of the RUSLE remain largely unclear,especially for the mountainous and hilly areas.In this study,we improved the RUSLE by considering quantitative impacts of different SWC measures on the P factor value.The improved RUSLE was validated against the long-term(2000-2015)soil erosion monitoring data obtained from 96 runoff plots(15—35°)in mountainous and hilly areas of Hubei Province,China;the result presented a high accuracy with the determination coefficient of 0.89.Based on the erosion monitoring data of 2018 and 2019,the Root Mean Square Error of the result by the improved RUSLE was 28.0%smaller than that by the original RUSLE with decrement of 19.6%—24.0%in the average P factor values,indicating that the soil erosion modelling accuracy was significantly enhanced by the improved RUSLE.Relatively low P factor values appeared for farmlands with tillage measures(P<0.53),grasslands with engineering measures(P<0.23),woodlands with biological measures(P<0.28),and other land use types with biological measures(P<0.51).The soil erosion modulus showed a downward trend with the corresponding values of 1681.21,1673.14,1594.70,1482.40 and 1437.50 t km^(-2)a-1 in 2000,2005,2010,2015 and 2019,respectively.The applicability of the improved RUSLE was verified by the measurements in typical mountainous and hilly areas of Hubei Province,China,and arrangements of SWC measures of this area were proposed.
基金This study was supported by the Science Foundation of the Hubei Province,China(2021CFB295)the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(A314021402–202110)the National Natural Science Foundation of China(42077451&42171415).
文摘Landscape alterations and ecosystem services(ES)are crucial elements that affect the socioecological development of ecologically fragile regions.To provide scientific support for the land-use planning and regional ecological restoration to achieve sustainable development goals(SDGs)in the Loess Plateau from 1992 to 2015,this study proposes an integrated assessment framework for assessing the supply-demand match and equilibrium of ES combining potential relationships between landscape alterations,ES,and sustainable development at the county and regional scales.Results show that more than 85%of local counties have a supply-demand mismatch in terms of ecosystem services.Supply-demand distributions for provisioning and supporting services were relatively balanced compared to cultural services,which were imbalanced.Although the overall supply-demand relationship is relatively balanced because of the significant influence of ecological restoration,it shows an increasing trend toward imbalance as human-land conflict is prominent in some regions.SDGs emphasize on specific ES information such as ecosystem conservation,sustainable agriculture,and urban construction.Furtherly,positive impacts from landscape dynamics can improve the supply capacity of the ES and contribute to regional sustainability.
文摘Rare earth element(REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different REE on different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amount increases with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4.3 and 5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amount. The new REE tracer method should be useful to future studying of erosion processes on slope lands.
基金The work was funded by the Natural Science Basic Research Program of Shaanxi Province(2021JQ-165)China Postdoctoral Science Foundation(2020M683591)Key National Research and Development Program of China(2016YFC0501604).
文摘Evaluating the effects of revegetation on runoff and erosion reduction is essential for studying soil and water conservation on the Loess Plateau after implementation of China's Grain for Green Project.However,quantifying the influence of revegetation on the erosion caused by concentrated runoff in extreme rainstorms is still challenging.To evaluate this influence,scouring-erosion experiments were implemented in situ on the vegetated hillslope plots(GR)and bare hillslope plots(CK).The runoffreducing effects of grass(GRR)averaged 31%,20%and 8%,and the erosion-reducing effects of grass(GER)averaged 93%,95%and 93%on the 5-plots,10-plots and 18-plots,respectively.The ratios of GRR to GER were 0.09e0.33,implying that the ability of vegetation to reduce erosion was greater than its ability to reduce runoff.The GRR and GER obviously decreased as the inflow rate increased,and the GRR decreased as the hillslope gradient increased,but there were no obvious differences in the GER between hillslope gradients.Vegetation could decrease the ability of the concentrated flow to carry and transport sediment and increase the energy consumption of the concentrated flow in response to hydraulic resistance.Vegetation also significantly reduced the degree of rill development.The degree of rill dissection on the GR(0.054e0.087 m^(2)m^(2))was lower than that on the CK(0.061e0.184 m^(2)m^(2)).Our findings provide an essential reference for ecological environment and vegetation restoration on loess hillslopes.
文摘The loessal hill region in southern Ningxia is a semiarid and severe eroded area with developed agriculture and animal husbandry. It has long been an argument whether there might be more potentiality of farming and whether food production can be sustained at a level of local sufficiency.
基金This work was supported by the National Natural Science Foundation of China(Grant no.41571274 and 41230746)the Foundation of State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau under project(Grant no.10501-1209).
文摘Hydrodynamic dispersion is a measure for describing the process of solute transport in porous media.Characterizing the dispersion of water flow within gravel is essential for the prediction of solute transport especially nonpoint source pollutants migration in alpine watersheds where the land surface is typically covered with gravel.In this study,an integrated model and experimental method using an electrolyte tracer is proposed for determination of the hydrodynamic dispersion coefficient.Two experimental scenarios were designed to measure electrolyte tracer transport processes in both free water flow and gravel layer flow under different slope gradients and transport distances.Subsequently,the measured data were used to simultaneously calculate both the hydrodynamic dispersion coefficient and flow velocity by fitting the experimental data with the mathematical model.Dispersivity,as a critical feature of hydrodynamic dispersion,was determined as well under the two specified scenarios.Finally,the impact mechanisms of the gravel layer and factors related to the dispersion processes were comprehensively analyzed.The results indicate that the presence of a gravel layer significantly reduces flow velocity and the hydrodynamic dispersion coefficient,but increases solute dispersivity.For the flow within gravel layers,with much lower velocity,the positive effect of the gravel layer on dispersivity may be neutralized or even surpassed by the negative effect of flow velocity.The results should be helpful in characterizing the dispersion processes of water flow within gravel layer and hence in predicting solute transport,especially in nonpoint source pollutants migration in alpine watersheds where the land surface is richly covered with gravel.