Characteristics and stability of slope movement response to underground mining of shallow coal seams away from gullies

Underground pressure is abnormal during mining of shallow coal seams under gullies. We studied gully slope movements, subject to underground mining, with physical simulation and theoretical analysis. The rules disclose that the slope rock slides horizontally in response to mining in the direction of gullies and rotates reversely with the appearance of a polygon block in mining away from gullies. We focused our attention on the case of mining away from a gully. We built a mechanical model in terms of a polygon block hinged structure and investigated the variation of horizontal thrust and shear force at the hinged point in relation to the rotation angle under different fragmentations. The Sliding-Rotation instability conditions of the polygon block hinged structure are presented based on the analyses of sliding instability and rotation instability. These results can serve as a theoretical guide for roof control during mining away from gullies in a coalfield defined by gullies.

Cultivating Erect Milkvetch (Astragalus adsurgens Pall.) (Leguminosae) Improved Soil Properties inLoess Hilly and Gulliesin China

Erect milkvetch （Astragalus adsurgens Pall.）, a leguminous grass, is a major source of fuel and forage, and has an important role in the restoration of the degraded ecosystems in central and northeastern China. The objective of this work was to investigate how erect milkvetch planting would affect the physical and chemical properties of soil in degraded arable lands. Soil samples at the depths of 0-20 and 20-40 cm were collected from erect milkvetch planting fileds at ages of 0, 1, 2 and 3 yr. Changes in soil bulk density, soil porosity, total N and P, organic matter content, available P, hydrolysable N and available K were measured. The results showed that root biomass and above-ground plant biomass were both significantly increased with plantation age. The significant increase in root nodule biomass was not observed in the first two years. However, it was significantly increased after three years. Root growth of erect milkvetch improved soil structure, and hence, decreased soil bulk density and increased soil porosity. Furthermore, the nitrogen fixation by erect milkvetch and return of erect milkvetch plant to soil increased the soil total N, hydrolysable N and organic matter content of the soil. Low concentrations of P in the soil with erect milkvetch planting could be ascribed to high plant uptakes and possibly to high sequestrations of P in plant biomass. Concentrations of K significantly increased during the first two years of erect milkvetch planting. The high accumulation of K under erect milkvetch cultivation in the first two years could partly be attributed to low plant uptake, and partly to relatively quick recycling within plant-soil systems. Three years after erect milkvetch plantingr, K accumulation at 0-20 cm soil layer was significantly lower than that from non-vegetated field sites, which could be attributed to high plant uptake. These parameters, except for soil bulk density, were all decreased with increasing soil depth. Soil total N, organic matter, porosity and available K in the 20-40 cm layer all showed linear increase trends, and soil bulk density, total P and available P in the depth 0-20 cm layer soil were decreased with increasing planting age. Erect milkvetch establishment could be an effective and applicable measure to improve soil nutrients, and prevent further soil degradation and erosion.

Remote Sensing Monitoring of Gullies on a Regional Scale: A Case Study of Kebai Region in Heilongjiang Province, China

Gully erosion is one of the major causes of land degradation in most areas and attracts increasing attention from researchers. We monitored gullies in the Kebai region in Heilongjiang Province of China by using remote sensing data and found that gully density increased with the increase in slope when the slope was less than 3°. Gully density in sunny slopes or windward slopes was greater than in shady slopes or leeward slopes because of the impacts of freezing and thawing, wind and solar radiation. Specifically, the gully density in northeast slope was the greatest and in southwest was the smallest. Gully density was reduced with increasing slope length and the longer the slope length, the less the gully density changed between 1965 and 2005. Affected by runoff, gullies most easily to occur in concave slopes and the critical elevation for gully erosion was 250–275 m. Moreover, hilly regions had the greatest gully density, followed by tableland regions, whereas the gully density in flatlands was the lowest. However, the gully density of these three types of landforms all increased between 1945 and 2000, and the portion of increase was 57.45%(hill), 52.91%(mesa) and 25.32%(plain), respectively.

Identifying ephemeral gullies from high-resolution images and DEMs using flow-directional detection

Ephemeral gullies,which are widely developed worldwide and threaten farmlands,have aroused a growing concern.Identifying and mapping gullies are generally considered prerequisites of gully erosion assessment.However,ephemeral gully mapping remains a challenge.In this study,we proposed a flow-directional detection for identifying ephemeral gullies from high-resolution images and digital elevation models(DEMs).Ephemeral gullies exhibit clear linear features in high-resolution images.An edge detection operator was initially used to identify linear features from high-resolution images.Then,according to gully erosion mechanism,the flow-directional detection was designed.Edge images obtained from edge detection and flow directions obtained from DEMs were used to implement the flow-directional detection that detects ephemeral gullies along the flow direction.Results from ten study areas in the Loess Plateau of China showed that ranges of precision,recall,and Fmeasure are 6 o.66%-90.47%,65.74%-94.98%,and63.10%-91.93%,respectively.The proposed method is flexible and can be used with various images and DEMs.However,analysis of the effect of DEM resolution and accuracy showed that DEM resolution only demonstrates a minor effect on the detection results.Conversely,DEM accuracy influences the detection result and is more important than the DEM resolution.The worse the vertical accuracy of DEM,the lower the performance of the flow-directional detection will be.This work is beneficial to research related to monitoring gully erosion and assessing soil loss.

Initial floristic composition of rehabilitated gullies through bioengineering in the Mixteca Region, Sierra Madre del Sur, Mexico

Re-vegetation plays a fundamental role for erosion control and plant recovery in lands affected by gully erosion. Bioengineered practices facilitate the gullies rehabilitation. Objectives of the research were: 1) Identify taxonomically the pioneer vegetation on each gully section; 2) Characterize vegetation distribution preferences and 3) Assess structural/functional traits to recognize erosion control key species. Bioengineering was applied in a watershed belonging to Sierra Madre del Sur, at Oaxaca, Mexico, on eight gullies, with local support and minimal investment. "La Mixteca" is a poor ecological and socio-economic region, comparable to other regions of the world. The Initial Floristic Composition(IFC) inventory is the baseline of the successional process. The transect method was used to determine the colonization of species. Cover abundance of registered species was estimated using the semi-quantitative scale of Braun-Blanquet. This procedure was repeated in five different positions(floor, hillslopes and tops), in the cross section of the gully. Throughcorrespondence analysis and clustering, the distribution of species was analyzed. Adequate responses were obtained in soil retention(quantity) and plant cover(existence and diversity); as measurable indicators of the bioengeneering works efficiency. Occupation of soil by native species from the Tropical Deciduous Forest was favored using live barriers. We detected species guilds with spatial distribution preferences in the gullies cross section. Plant cover characterization includes: native colonizer species, herbaceous, shrubby and trees of the forest community bordering the gully area, with cover abundance and structural/functional traits, useful to protect degraded areas. This spatial occupation process of plants responds to a secondary succession in gullies, where the proposed IFC model is correctly represented through bioengineering. Natural establishment of plants was successful by traits of species such as extensive root system and sexual/vegetative reproduction.

Morphology and controlling factors of the longitudinal profile of gullies in the Yuanmou dry-hot valley

The morphology of the gully longitudinal profile （GLP） is an important topographic index of the gully bottom associated with the evolution of the gullies. This index can be used to predict the development trend and evaluate the eroded volumes and soil losses by gullying. To depict the morphology of GLP and understand its controlling factors, the Global Positioning System Real-time Kinematic （GPS RTK） and the total station were used to measure the detail points along the gully bottom of 122 gullies at six sites of the Yuanmou dry-hot Valley. Then, nine parameters including length （Lt）, horizontal distance （Dh）, height （H）, vertical erosional area （A）, vertical curvature （Co）, concavity （Ca）, average gradient （Ga）, gully length-gradient index （GL）, normalized gully length-gradient index （Ngl）, were calculated and mapped using CASS, Excel and SPSS. The results showed that this study area is dominated by slightly concave and medium gradient GLPs, and the lithology of most gullies is sandstone and siltstone. Although different types of GLPs appear at different sites, all parameters present a positively skewed distribution. There are relatively strong correlations between several parameters： namely Lt and H, Dh and H, Lt and A, Dh and A, H and GL. Most GLPs, except three, have a best fit of exponential functions with quasi- straight shapes. Soil properties, vegetation coverage, piping erosion and topography are important factors to affect the GLP morphology. This study provides useful insight into the knowledge of GLP morphology and its influential factors that are of critical importance to prevent and control gully erosion.

Impacts of native vegetation on the hydraulic properties of the concentrated flows in bank gullies

To quantify the impacts of native vegetation on the spatial and temporal variations in hydraulic properties of bank gully concentrated flows,a series of in situ flume experiments in the bank gully were performed at the Yuanmou Gully Erosion and Collapse Experimental Station in the dry-hot valley region of the Jinsha River,Southwest China.This experiment involved upstream catchment areas withone-and two-year native grass(Heteropogon contortus)and bare land drained to bare gully headcuts,i.e.,Gullies 1,2 and 3.In Gully 4,Heteropogon contortus and Agave sisalana were planted in the upstream catchment area and gully bed,respectively.Among these experiments,the sediment concentration in runoff in Gully 3 was the highest and that in Gully 2 was the lowest,clearly indicating that the sediment concentration in runoff obviously decreased and the deposition of sediment obviously increased as the vegetation cover increased.The concentrated flows were turbulent in response to the flow discharge.The concentrated flows in the gully zones with native grass and bare land were sub-and supercritical,respectively.The flow rate and shear stress in Gully 3 upstream catchment area were highest among the four upstream catchment areas,while the flow rate and shear stress in the gully bed of Gully 4 were lowest among the four gully beds,indicating that native grass notably decreased the bank gully flow rate and shear stress.The Darcy–Weisbach friction factor(resistance f)and flow energy consumption in the gully bed of Gully 4 were notably higher than those in the other three gully beds,clearly indicating that native grass increased the bank gully surface resistance and flow energy consumption.The Reynolds number(Re),flow rate,shear stress,resistance f,and flow energy consumption in the gully beds and upstream areas increased over time,while the sediment concentration in runoff and Froude number(Fr)decreased.Overall,increasing vegetation cover in upstream catchment areas and downstream gully beds of the bank gully is essential for gully erosion mitigation.

Effects of soil shrinkage in permanent gullies formation: The case of Benggang erosion in the granite area of southern China

Soil shrinkage is an important factor in slope destabilization in granitic areas, which is also one of the most important conditions for the formation of permanent gullies. This study explored the effect of soil shrinkage on permanent gullies, and Benggang erosion in granitic areas in southeastern China was used as an example. Three types of Benggang in granitic area were selected to examine the soil shrinkage of three soil layers(the lateritic, transitional and sandy layers) and their effect on the development of Benggang erosion was studied. The results show that the maximum values of COLEH and COLEV(coefficient of linear extensibility in horizontal and vertical directions, respectively) are 3.09% and 1.60% in the laterite layers, 2.71% and 2.13% in transition layers, and 1.10% and 1.82% in sandy layers, indicating that the shrinkage potential of the soil layers exhibits the following order, from highest to lowest: the laterite layer, transition layer, and sandy layer. With a decreasing volumetric water content, the linear shrinkage ratio increases gradually and eventually stabilizes, and in the laterite, transition and sandy layers, the average values of the maximum linear shrinkage are 1.50%, 2.09%, and 1.74%, respectively. Axial shrinkage is most obvious in the transition layers, in which the volume change in the form of subsidence is greater than that in other layers. The soil shrinkage curves fit the trilinear model(R2>0.9), and the soil shrinkage characteristic curves were divided into structural, basic, and residual sections. The correlation analysis shows that the soil shrinkage rate is positively correlated with clay and Fe2 O3 content and negatively correlated with sand content. Clay and sand contents are the most important factors influencing soil shrinkage. Soil oxides can influence soil shrinkage by affecting the particle composition of the soil, so soil shrinkage is closely related to soil clay minerals. Our findings can provide a theoretical basis for revealing the mechanism of Benggang erosion and its control.

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.

Planar morphology and controlling factors of the gullies in the Yuanmou Dry-hot Valley based on field investigation

The plane form of a gully can provide a basis for evaluating the gully volume and erosion rate, acting process, and evolutionary stage. For describing the planar characteristics of a permanent gully and understanding their controlling factors, this study, utilizing a total station and GPS RTK, measured the shoulder lines and channel curves of 112 gullies in six sites of the Yuanmou Dry-hot Valley and then mapped them by Arc GIS software and calculated nine parameters. The results showed that the channel lengths range from 10.88 to 249.11 m; the widths range from 6.20 to 40.99 m; the perimeters range from 54.11 to 541.67 m; the gully areas range from 153.02 to 6,930.30 m2; the left-side areas range from 92.93 to 4,027.20 m2; and the right-side areas range from 63.65 to 3,539.77 m2. The slightly sinuous and straight gullies account for 73.21% of the total gullies; the quantity of the right skewed gullies is 8.93% greater than that of the left skewed ones based on the symmetry ratio; the shape ratios range from 1.12 to 1.40 and the morphology ratios from 0.038 to 1.294; the fractal dimension is 1.192. Gullies in different sites have diverse planar characteristics. Except for the symmetry index, which was close to a negatively skewed distribution, all of the other parameters had the characteristic of positively skewed distribution. The gully area is related to the length and width, but the gully length has a weak correlation with the width. The evolutionary stage, topographic conditions, strata, soil properties, and piping erosion played very important roles in the gully planar morphology. This study could provide useful information for controlling gully erosion and safeguarding human habitation and engineering buildings.

Effectiveness of measures aiming to stabilize urban gullies in tropical cities:Results from field surveys across D.R.Congo

Urban gullies are a rapidly growing concern in many tropical cities of the Global South.Various measures are already implemented for their stabilization.However,an overview of these measures and their overall effectivenesss is currently lacking.We aim at addressing this gap by documenting existing ini-tiatives to stabilize urban gullies in D.R.Congo and assessing their overall effectiveness.To this end we conducted extensive field campaigns in Kinshasa,Kikwit and Bukavu and combined our terrain obser-vations with data on gully expansion rates(derived from series of satellite imagery).In total,we char-acterized present and past stabilization initiatives for 398 urban gullies.For 69 of these gullies,the effect of a specific measure on gully expansion rates could be estimated.Results show that for the large ma-jority of gullies,various measures have been implemented.Yet,these are mainly ad-hoc measures installed by the affected population.More structural measures based on larger engineering works were observed for only 20-30%of gullies.The huge efforts invested in the installation of measures strongly contrast with their overall low impact Among all strategies,only the deviation of runoff resulted in significantly lower expansion rates after installation.The numerous initiatives that rely on the sparse means available seem to have limited effects.This does not imply,however,that they are completely ineffective and should be abandoned.Based on our findings,we formulate recommendations for further research on how to effectively prevent and stabilize urban gullies,taking into account the difficult environmental and socio-economic context.

Analysis of debris flow control effect and hazard assessment in Xinqiao Gully,Wenchuan M_(s)8.0 earthquake area based on numerical simulation

Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.

Effect of coir geotextile and geocell on ephemeral gully erosion in the Mollisol region of Northeast China

The unique geomorphological features and farming methods in the Mollisol region of Northeast China increase water catchment flow and aggravate the erosion of ephemeral gully(EG).Vegetation suffers from rain erosion and damage during the growth stage,which brings serious problems to the restoration of grass in the early stage.Therefore,effects of coir geotextile and geocell on EG erosion under four confluence intensities were researched in this study.Results of the simulated water discharge erosion test showed that when the confluence strength was less than 30 L/min,geocell and coir geotextile had a good effect on controlling EG erosion,and sediment yield of geocell and coir geotextile was reduced by 25.95%–37.82%and 73.73%–88.96%,respectively.However,when confluence intensity increased to 40 L/min,protective effect of coir geotextile decreased,and sediment yield rate increased sharply by 189.03%.When confluence intensity increased to 50 L/min,the protective effect of coir geotextile was lost.On the other hand,geocell showed that the greater the flow rate,the better the protective effect.In addition,with the increase in confluence intensity,erosion pattern of coir geotextile developed from sheet erosion to intermittent fall and then to completion of main rill,and the protective effect was gradually weakened.In contrast,the protective effect of EG under geocell was gradually enhanced from the continuous rill to the intermittent rill and finally to the intermittent fall.This study shows that coir geotextile and geocell can prevent EG erosion,and the effect of geocell is better than that of coir geotextile on the surface of EG.

Mapping and understanding degradation of alpine wetlands in the northern Maloti-Drakensberg, southern Africa

The alpine terrestrials of the Maloti-Drakensberg in southern Africa play crucial roles in ecosystem functions and livelihoods,yet they face escalating degradation from various factors including overgrazing and climate change.This study employs advanced Digital Soil Mapping(DSM)techniques coupled with remote sensing to map and assess wetland coverage and degradation in the northern Maloti-Drakensberg.The model achieved high accuracies of 96%and 92%for training and validation data,respectively,with Kappa statistics of 0.91 and 0.83,marking a pioneering automated attempt at wetland mapping in this region.Terrain attributes such as terrain wetness index(TWI)and valley depth(VD)exhibit significant positive correlations with wetland coverage and erosion gully density,Channel Network Depth and slope were negative correlated.Gully density analysis revealed terrain attributes as dominant factors driving degradation,highlighting the need to consider catchment-specific susceptibility to erosion.This challenge traditional assumptions which mainly attribute wetland degradation to external forces such as livestock overgrazing,ice rate activity and climate change.The sensitivity map produced could serve as a basis for Integrated Catchment Management(ICM)projects,facilitating tailored conservation strategies.Future research should expand on this work to include other highland areas,explore additional covariates,and categorize wetlands based on hydroperiod and sensitivity to degradation.This comprehensive study underscores the potential of DSM and remote sensing in accurately assessing and managing wetland ecosystems,crucial for sustainable resource management in alpine regions.

Failure mechanism and simulation for long run-out of the catastrophic rock landslide in the Shanyang Vanadium Mine,China

On 12th August 2015,a massive rapid long run-out rock landslide occurred in the Shanyang Vanadium Mine in Shaanxi Province,China,which claimed the lives of 65 miners.No heavy rainfalls,earthquakes,and mining blasts were recorded before the incident.Therefore,the failure mechanism and the cause of the long run-out movement are always in arguments.In this paper,we conducted a detailed field investigation,laboratory tests,block theory analysis,and numerical simulation to investigate the failure and long run-out mechanisms of the landslide.The field investigation results show that the source material of the rock landslide is a huge dolomite wedge block bedding on siliceous shale layers.Uniaxial compression tests indicate that the uniaxial compression strength of the intact dolomite is 130-140MPa and the dolomite shows a brittle failure mode.Due to the progressive downward erosion of the gully,the dolomite rock bridge at the slope toe became thinner.As the compression stress in the dolomite bridge increased to surpass its strength,the brittle failure of the bridge occurred.Then huge potential energy was released following the disintegration of the landslide,which led to the high acceleration of this rock landslide.The 3D discrete element simulation results suggest that the low intergranular friction contributes to the long run-out movement of this rock landslide.

Spatiotemporal variations in ecosystem services and their trade-offs and synergies against the background of the gully control and land consolidation project on the Loess Plateau,China

Studying the spatiotemporal variations in ecosystem services and their interrelationships on the Loess Plateau against the background of the gully control and land consolidation(GCLC)project has significant implications for ecological protection and quality development of the Yellow River Basin.Therefore,in this study,we took Yan'an City,Shaanxi Province of China,as the study area,selected four typical ecosystem services,including soil conservation service,water yield service,carbon storage service,and habitat quality service,and quantitatively evaluated the spatiotemporal variation characteristics and trade-offs and synergies of ecosystem services from 2010 to 2018 using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.We also analysed the relationship between the GCLC project and regional ecosystem service changes in various regions(including 1 city,2 districts,and 10 counties)of Yan'an City and proposed a coordinated development strategy between the GCLC project and the ecological environment.The results showed that,from 2010 to 2018,soil conservation service decreased by 7.76%,while the other three ecosystem services changed relatively little,with water yield service increasing by 0.56% and carbon storage service and habitat quality service decreasing by 0.16% and 0.14%,respectively.The ecological environment of Yan'an City developed in a balanced way between 2010 and 2018,and the four ecosystem services showed synergistic relationships,among which the synergistic relationships between soil conservation service and water yield service and between carbon storage service and habitat quality service were significant.The GCLC project had a negative impact on the ecosystem services of Yan'an City,and the impact on carbon storage service was more significant.This study provides a theoretical basis for the scientific evaluation of the ecological benefits of the GCLC project and the realization of a win-win situation between food security and ecological security.

Soil and Crop Damages as a Result of Levee Breaches on Ohio and Mississippi Rivers

Whenever levees on the Ohio or Mississippi rivers are breached, there are soil damages in the flooded areas that impact agricultural management capacities and crop productivity. Floodwaters coat the entire flooded land surface with sediments which include a variety of pollutants, nutrients and contaminants. The nature of the sediments in floodwaters varies with the topographical and land use characteristics of the watershed. The soil types, hydro-geologic features, volume of flow, time of year, agricultural use of fertilizers, pesticides, and other chemicals as well as upstream point sources such as sewage treatment plants, storm sewer drainage and other urban land uses will affect the extent of the contamination and fine scale remediation needed. Preliminary characterization and measurement of soils and sediment deposit at three locations that experienced recent natural and man induced levee breaches are analyzed to identify patterns of soil and crop damage. These findings provide guidance to the restoration of craters, gullies, land scoured areas and contaminated sediment depositional sites with a goal to improve decision-making, risk analysis and remedial effectiveness. Recommendations include： （1） improve characterization and measurement of eroded soils and distribution of sediment contaminants after levee breaching; （2） assess contamination effects on soil productivity and long term agricultural production in order to understand the impacts of flooding on agricultural soils; （3） evaluate reconstruction investments needed to repair levees based on return of the land to productivity and increased landscape resilience by reducing vulnerability to future flooding and levee breaching stress.

Impact of Gully on Soil Moisture of Shrubland in Wind-Water Erosion Crisscross Region of the Loess Plateau

The most serious erosion on the Loess Plateau of China exists in the wind-water erosion crisscross region where the annual precipitation is about 400 mm,the ecological environment is very fragile,and water is the key limiting factor for improving the environment. In this study,changes of soil moisture content for Caragana korshinskii Kom. shrubland in the gully bank of the Loess Plateau were studied using the methods of soil sampling and neutron probe. A typical gully(75 m long,28 m wide,and 10 m deep) was selected,and six neutron probe access tubes(6 m long) were installed at points 50,100,200,300,400,and 500 cm from the gully border for obtaining soil moisture data from July to October 2004 at approximately 10 d intervals. Soil samplings were simultaneously carried out for moisture determination at the six points. Results showed that the soil moisture of the shrubland in the gully bank significantly varied between 300 and 400 cm in the horizontal direction and up to 600 cm in vertical direction of the gully. Seasonal changes in soil moisture revealed a curve with a single peak that occurred at the end of August or early September. A linear regression equation was fit for soil water storage and the distance from the gully border,with coefficients depending on rainfall characteristics,sampling point,and time of measurement.

Evapotranspiration and Soil Moisture Balance for Vegetative Restoration in a Gully Catchment on the Loess Plateau, China

Evapotranspiration, soil moisture balance and the dynamics in a gully catchment of the Loess Plateau in China were determined with 6 land use treatments including natural grassland, shrubs （Caragana rnicrophylla）, two woodlands （Prunus armeniaca var. ansu and Pinus tabulaeformis）, cultivated fallow, and farmland （Triticum aestiuum L.） in order to obtain a better understanding of soil moisture balance principles and to improve vegetation restoration efficiency for ecological rebuilding on the plateau. Average runoff from cultivated fallow was very high, reaching 10.3% of the seasonal rainfall. Evapotranspiration under T. aestivurn was not significantly different from natural grasslands. Compared with natural grass, evapotranspiration was significantly greater （P 〈 0.05） in 2002 and there was an increase in soil moisture depleted in the 1-3 m soil under P. armeniaca, P. tabulaeformis and C. microphylla. During the two years of the study the average soil moisture （0-100 cm soil profile） of T. aestivurn was generally the highest, with P. armeniaca, P. tabulaeformis and C. rnicrophylla usually the lowest. Thus, according to the soil moisture balance principle for this area the planned reforestation project was not ecologically reasonable. Reducing human disturbance and restoration with grass could be more effective.

Effects of Gully Erosion and Gully Filling on Soil Degradation in the Black Soil Region of Northeast China

Gully erosion has caused soil degradation and even reduced soil productivity. However, only few studies on the effects of gully erosion and artificial controlling measures on soil degradation in the Black Soil Region of Northeast China are available. Thus, this study explores the relationships between gully erosion, gully filling and soil parameters. Two sets of soil samples were collected in the field at： （1） 72 sample points in the gully erosion study area, 60 sample points in the ephemeral and classical gully erosion area （3,518 m2）, 12 sample points in the deposition zone （443 m2）, （2）1o reference points along a slope unaffected by gully erosion representing the original situation before the gully was formed. All soil samples were analyzed for gravel content （GC）, soil organic matter （SOM）, total nitrogen （TN）, available nitrogen （AN）, available phosphorus （AP）, and available potassium （AK）. The soil property values on unaffected slope were fitted by the polynomial curves as the reference values in no gully erosion area. The interpolated soil property values in gully eroded study area were compared with these polynomial curves, respectively, and then, changes of soil property values were analyzed. Gully erosion caused an increase in GC and a decrease in SOM, TN, AN, AP and AK. The change of GC, SOM, TN, AN, AP, AK was 8.8%, -9.04 g kg-1, -0.92 g kg-1, -62.28 mg kg-1, -29.61 mg kg% -79.68 mg kg-1. The soil property values in the study area were below optimal values. Thus, we concluded that gully erosion and gully filling caused both on-site and off-site soil degradation. Soil degradation area was 0.65 % of the cultivated land. In addition, it was proved that gully filling were an improper soil and water conservation measure, which seems to exacerbate the problem. Thus, it is suggested that soil where soil is deep is moved to fill the gully, and then the area around the filled gullies should be covered by grass for preventing the formation and development of the gully.