Erosion Regions Research Articles

Estimation of soil loss by USLE Model using Remote Sensing and GIS Techniques - A Case study of Coastal Odisha, India

Globally, Soil erosion is the major land degradation problem, which impacts seriously on economic and environmental status. Geospatial techniques support and provided quantitative approach to estimate soil erosion in different conditions. In the present study, Revised Universal Soil Loss Equation (RUSLE) integrated with GIS has been used to estimate soil loss in the part of coastal Odisha system. The study area, Ganjam block have undulating topography covering 0-35% slopes. The quantitative soil loss was estimated and classified into different classes and soil erosion map was generated. The soil erosion map is classified into seven classes from very slight (<5 t ha -1 yr -1 ) to extremely severe (>80 t ha -1 yr -1 ). The results indicate that 90.9% (22330 ha) of the study area falls in very low erosion category, which may be due to level topography and regular vegetation cover. The other erosion classes such as moderate, high and very high erosion occurred in the range of 2.12%, 2.23% and 1.49 %, respectively. The high soil erosion risk is spatially situated in the foothills and upper steep slope of the area. The results can certainly aid in implementation of soil management and conservation practices to reduce the soil erosion in the coastal Odisha regions of Eastern India.

Scale effects of vegetation restoration on soil and water conservation in a semi-arid region in China: Resources conservation and sustainable management

The scale effect of vegetation restoration on soil and water conservation has received little attention, despite numerous studies on the assessments of vegetation restoration at different spatial scales. This study investigated the scale effect of vegetation restoration on soil erosion and water yield at Yanhe watershed, Chinese Loess Plateau. It provides the site-based temporal and spatial varying relationships among vegetation restoration, soil erosion, and water yield. Spatial modeling and mapping methods were used to analyze the scale effect at regional and sub-watershed scales. Our results indicated vegetation restoration has generated positive impacts on soil erosion reduction and negative impacts on water provision in the whole watershed. Croplands, sparse grasslands, and moderate grasslands were the land types which contributed the most to soil erosion. The decrease of cropland was the major contribution to soil erosion reduction. Moreover, the trade-off relationship between soil erosion and water yield existed in the whole watershed, but the degree of trade-off varied from one sub-watershed to another. High-risk soil erosion regions were concentrated in the central watershed. But in this region, the impacts of vegetation restoration on soil erosion control varied with different sub-watersheds. A simple increase of vegetation might not help reduce soil erosion in sub-watersheds where are characterized by low vegetation coverage and scattered vegetation restoration. Vegetation restoration should be based on past spatial LULC patterns. Soil erosion control should focus on the current level of cropland management and areas of vegetation maintenance than new afforestation in the high-risk soil erosion regions.

Dynamic Simulation of Erosion Failure of a Hydraulic Jet Tool via Discrete Phase Model

Hydraulic perforating technology uses the erosion of high-velocity solid–liquid flow to punch or cut the target wall. During the perforating process, the high-velocity two-phase flow will bound back to the outer wall of the tool to cause erosion damage, and in severe cases, the tool will fail. In this paper, the discrete phase model was used to obtain the parameters of particles rebound from target wall, and then get the erosion characteristics of outer wall of jet tool including erosion rate and erosion distribution. The critical parameters of 35CrMo erosion were obtained from a solid–liquid jet flow experiment. The calculated results show that the impact velocity and angle of particle on the tool surface are significantly affected by perforation depth. The erosion rate of outer wall of tool will decrease with the increase in perforating depth. The effect of jet flow velocity on eroded areas is more than erosion rate. From that, the erosion rate is mainly affected by the injection velocity of the perforating fluid, while the erosion region is determined by the perforation depth.

Advances in neutral tungsten ultraviolet spectroscopy for the potential benefit to gross erosion diagnosis

A spectral survey of tungsten emission in the ultraviolet region has been completed in the DIII-D tokamak and the CTH torsatron to assess the potential benefit of UV emission for the diagnosis of gross W erosion. A total of 29 W I spectral lines are observed from the two experiments using survey spectrometers between 200 and 400 nm with level identifications provided based on a structure calculation for many of the excited states that produce strong emission lines. Of the 29 observed lines, 20 have not previously been reported in fusion relevant plasmas, including an intense line at 265.65 nm which could be important for benchmarking the frequently exploited line at 400.88 nm. Nearly all of the observed spectral lines decay down to one of the six lowest energy levels for neutral W, which are likely to be long-lived metastable states. The impact of metastable level populations on the W I emission spectrum and any erosion measurement utilizing a spectroscopic technique is potentially significant. Nevertheless, the high density of W I emission in the UV region allows for the possibly of determining the relative metastable fractions and plasma parameters local to the erosion region. Additionally, the lines observed in this work could be used to perform multiple independent gross erosion measurements, leading to more accurate diagnosis of gross tungsten erosion.

Impacts of Land-Use Changes on Soil Erosion in Water–Wind Crisscross Erosion Region of China

Soil erosion affects food production, biodiversity, biogeochemical cycles, hydrology, and climate. Land-use changes accelerated by intensive human activities are a dominant anthropogenic factor inducing soil erosion globally. However, the impacts of land-use-type changes on soil erosion dynamics over a continuous period for constructing a sustainable ecological environment has not been systematically quantified. This study investigates the spatial–temporal dynamics of land-use change and soil erosion across a specific area in China with water–wind crisscross erosion during three periods: 1995–1999, 2000–2005, and 2005–2010. We analyzed the impacts of each land-use-type conversion on the intensity changes of soil erosion caused by water and wind, respectively. The major findings include: (1) land-use change in the water–wind crisscross erosion region of China was characterized as cultivated land expansion at the main cost of grassland during 1995–2010; (2) the strongest land-use change moved westward in space from the central Loess Plateau area in 1995–2005 to the western piedmont alluvial area in 2005–2010; (3) soil erosion area is continuously increasing, but the trend is declining from the late 1990s to the late 2000s; (4) the soil conservation capability of land-use types in water–wind crisscross erosion regions could be compiled from high to low as high coverage grasslands, medium coverage grasslands, paddy, drylands, low coverage grasslands, built-up lands, unused land of sandy lands, the Gobi Desert, and bare soil. These findings could provide some insights for executing reasonable land-use approaches to balance human demands and environment sustainability.

Scarp orientation in regions of active aeolian erosion on Mars

The morphologies of wind-formed features on Mars provide diagnostic information about ancient and modern surface winds. Aeolian erosional features include decimeter-scale ventifacts and kilometer-scale yardangs, but intermediate-scale erosional features are less well-understood. Understanding aeolian erosion may be critical to identifying ancient martian biosignatures. Cosmogenic radiation destroys complex organic molecules during prolonged exposure at the martian surface, but outcrops freshly re-exposed by aeolian erosion provide potential sites where biosignatures could have been protected and made recently available for sampling. Wind-driven scarp retreat has been cited as the cause for young exposure ages measured in Gale crater.Upcoming exploration by the Mars 2020 rover will focus on Jezero crater, another location of extensive aeolian erosion and meter-scale scarps. This work is motivated by the hypothesis that retreating scarps on Mars may prefer orientations that reflect the direction of erosive winds. We mapped scarps in Jezero and Gale craters and compared their orientation distributions with local wind regimes interpreted from other aeolian indicators. No strong correlation between wind direction and scarp orientation was identified. The near-random distribution of scarp orientations suggests that in the locations studied the dominant processes controlling scarp orientation are either processes that do not prefer an orientation (e.g., impact or thermal fracturing processes), or that turbulent flow structures form at the scale of scarp topography and obscure the regional-scale signals of erosion with scarp-scale eddies and flow deflection.

Modeling Bedload Transport Trajectories along a Sine-Generated Channel

This study explores the influences of flow discharge and particle size on bedload transport trajectory by applying a depth-averaged two-dimensional model to a 110° sine-generated laboratory flume with wide-and-shallow sections. Calculated results exhibit two erosion regions in a bend: Zone-1—oreside of the point bar near the convex bank and Zone-2—near the apex of the concave bank. Sediments eroded from Zone-1 are mainly transported along the same-side convex bank rather than crossing the channel centerline, indicating the crucial role of longitudinal flow in shaping point bars. Most particles from Zone-2, however, behave more complicated by changing their trajectories with the developing bar-pool topography. Besides, sensitivity analyses indicate that, the shifting of bedload trajectory in the curved channel is not susceptible to particle size while considerably varies with flow discharge. Moving particles in a meandering channel are ultimately constrained within the belt of “concave bank‒crossing bar‒concave bank” after the bend topography is fully developed and the bed deformation reaches a dynamic equilibrium.

Patterns of legacy sediment deposits in a small South Carolina Piedmont catchment, USA

Anthropogeomorphic changes to channels and floodplains occurred in response to destructive agricultural practices following the arrival of European settlers into the Americas. The southeastern Piedmont physiographic region of the USA experienced severe erosion and sedimentation after settlement in the 1700s and farming up through the 1930s. In places, deep floodplain aggradation formed uninterrupted alluvial deposits that extend many kilometers. This research examines anthropogenic impacts of land-use change on valley bottom sedimentation in the Chicken Creek Watershed of South Carolina. Abrupt contacts between precolonial floodplain soils and a thick overburden of historical legacy sediment are common and well exposed throughout the two-km study reach and provide clear evidence of extensive postcolonial sedimentation. Soil stratigraphic and sedimentologic evidence are presented to identify and contrast pre- and postcolonial sediment characteristics and thicknesses. LiDAR-based spatial analysis is used to examine patterns of legacy sediment deposition and floodplain storage and—together with field observations of bank stratigraphy—examine the environments in which this occurred. Precolonial geomorphic stability is indicated by a buried soil epipedon (Ab horizon) and other features on precolonial floodplain surfaces.Legacy sediment 2 to 4 m thick rests on top of exposed precolonial soils throughout the stream corridor, with the pre−/postcolonial contact ~1.5 m above the channel bed on average. Linear regression analysis shows that legacy sediment thickness varies statistically with changes in valley width and proximity to tributary sediment sources. Thin precolonial alluvium over bedrock suggests modest erosion and sedimentation rates prior to the arrival of EuroAmerican settlers. Mean grain-sizes are similar between the pre- and postcolonial alluvium, but substantial contrasts in the degree of stratification and bulk density document differences between the respective depositional environments and post-depositional changes to the two units. Channel adjustments since the time of maximum aggradation include bed incision to at least as low as the precolonial longitudinal profile and widening that is ongoing.

Numerical Study of Solid Particle Erosion in a Centrifugal Pump for Liquid–Solid Flow

Solid particle erosion is a serious issue in centrifugal pumps that may result in economic losses. Erosion prediction in centrifugal pump is complex because the flow field inside it is three-dimensional (3D) unsteady and erosion can be affected by numerous factors. In this study, solid particle erosion of the entire centrifugal pump for liquid–solid flow is investigated numerically. Two-way coupled Eulerian–Lagrangian approach is adopted to calculate the liquid–solid interaction. The reflection model proposed by Grant and Tabakoff and the erosion model proposed by the Erosion/Corrosion Research Center are combined to calculate the erosion rate and predict the erosion pattern. Results show that for the baseline case, the inlet pipe is the least eroded component, whereas the impeller is the most eroded component. The highest average and maximum erosion rates occur at the hub of impeller. The most severe erosion region of a blade is the leading edge with a curvature angle that varies from 55 deg to 60 deg. The most severe erosion region of a volute is in the vicinity of a curvature angle of 270 deg. The impeller erosion pattern, especially the middle part of the hub and the vicinity of the blade pressure side, can be greatly influenced by operation parameters, such as flow rate, particle concentration, and particle size.

Topographic change and numerically modelled near surface wind flow in a bowl blowout

AbstractA number of studies have measured and numerically modelled near surface wind velocity over a range of aeolian landforms and made suppositions about topographic change and landform evolution. However, the precise measurement and correlation of flow dynamics and resulting topographic change have not yet been fully realized. Here, using repeated high‐resolution terrestrial laser scanning and numerical flow modelling within a bowl blowout, we statistically analyse the relationship between wind speed, vertical wind velocity, turbulent kinetic energy and topographic change over a 33‐day period.Topographic results showed that erosion and deposition occurred in distinct regions within the blowout. Deposition occurred in the upwind third of the deflation basin, where wind flow became separated and velocity and turbulent kinetic energy decreased, and erosion occurred in the downwind third of the deflation basin, where wind flow reattached and aligned with incident wind direction.Statistical analysis of wind flow and topographic change indicated that wind speed had a strong correlation with overall topographic change and that vertical wind velocity (including both positive and negative) displayed a strong correlation with negative topographic change (erosion). Only weak or very weak correlations exist for wind flow parameters and positive topographic change (accretion). This study demonstrates that wind flow modelling using average incident wind conditions can be utilized successfully to identify regions of overall change and erosion for a complex aeolian landform, but not to identify and predict regions where solely accretion will occur. © 2019 John Wiley &amp; Sons, Ltd.

An experimental study on the influences of water erosion on wind erosion in arid and semi-arid regions

Complex erosion by wind and water causes serious harm in arid and semi-arid regions. The interaction mechanisms between water erosion and wind erosion is the key to further our understanding of the complex erosion. Therefore, in-depth understandings of the influences of water erosion on wind erosion is needed. This research used a wind tunnel and two rainfall simulators to investigate the influences of water erosion on succeeding wind erosion. The wind erosion measurements before and after water erosion were run on semi-fixed aeolian sandy soil configured with three slopes (5°, 10° and 15°), six wind speeds (0, 9, 11, 13, 15 and 20 m/s), and five rainfall intensities (0, 30, 45, 60 and 75 mm/h). Results showed that water erosion generally restrained the succeeding wind erosion. At a same slope, the restraining effects decreased as rainfall intensity increased, which decreased from 70.63% to 50.20% with rainfall intensity increased from 30 to 75 mm/h. Rills shaped by water erosion could weaken the restraining effects at wind speed exceeding 15 m/s mainly by cutting through the fine grain layer, exposing the sand layer prone to wind erosion to airflow. In addition, the restraining effects varied greatly among different soil types. The restraining effects of rainfall on the succeeding wind erosion depend on the formation of a coarsening layer with a crust and a compact fine grain layer after rainfall. The findings can deepen the understanding of the complex erosion and provide scientific basis for regional soil and water conservation in arid and semi-arid regions.

Vulnerability assessment of the global water erosion tendency: Vegetation greening can partly offset increasing rainfall stress

AbstractGlobal water erosion is a grave threat to the sustainability of agriculture. Regional climate change may aggravate the threat of erosion, whereas global vegetation greening (an increasing trend in vegetation cover) may act as a mitigation to the threat. On the basis of the Revised Universal Soil Loss Equation, we assessed the vulnerability of the global water erosion during 1982–2015. A contribution index was built to describe the influences of rainfall erosivity and cover management on global water erosion vulnerability changes during 1982–2015. The research objective was to explore the spatial pattern of global water erosion vulnerability change in recent decades and to identify the factor that has contributed most to the vulnerability change, and three main results were obtained. (a) The global water erosion vulnerability increased over 51% of the surface during 1982–2015, and the surface with significant decreasing trends only accounted for 12% of the middle and highly sensitive areas. (b) Rainfall erosivity contributed more than cover management for absolute value except in the Amazon, Congo Basin, and Southeast Asia, whereas the contribution of cover management was increasing. (c) Vegetation greening can partly offset the stress caused by climate change. The global water erosion vulnerability decreased more than increased in sensitive area. Consequently, enhancing the vegetation growth in the highly sensitive water erosion region could reduce the erosion threat at large scale.

Rapid Increase in the Lateral Transport of Trace Elements Induced by Soil Erosion in Major Karst Regions in China.

Soil erosion, which has been recently shown to significantly perturb carbon cycling, occurs naturally but can be either enhanced or reduced by human activities. However, the impacts of soil erosion on terrestrial contaminant cycles remain unclear. Here, we select eight trace elements, i.e., arsenic, cadmium, chromium, copper, nickel, lead, zinc, and mercury, to examine the erosional impacts of the elements' fate and transport across China. By synthesizing the detailed distribution of soil erosion fluxes, soil element inventories, and diverse modeling methods, we reveal that while human activities have reduced the lateral transport of these elements in the Loess Plateau (Central North China, a 56% decline in the past two decades with a range of 46% to 110%) due to soil conservation projects, they have increased these transport fluxes in China's major karst regions (Southwest China, a 84% increase with a range of 55% to 150%) because of severe rocky desertification. These fluxes have completely overwhelmed the soil conservation efforts in the Loess Plateau. Fluxes of these elements into aquatic environments from Southwest China reached 46% of the total input in China in 2010. These fluxes were higher than the inputs from point sources in the region by a factor of 50 because of impacts of excessive agricultural cultivation and geographical and climatic factors. These findings indicate the enormous perturbation of terrestrial contaminant cycles caused by soil erosion in karst regions and demonstrate the need for long-term sustainable management of soil erosion and contaminant discharge to protect fragile terrestrial ecosystems.

Soil properties across a chronosequence of Ailanthus altissima in semiarid plantations

Afforestation is a main tool for preventing desertification and soil erosion in arid and semiarid regions of Iran. Large-scale afforestation, however, has poorly understood consequences for the future ecosystems in the term of ecosystems protection. The objective of the present study is to identify changes in soil properties following different intervals of planting of Ailanthus altissima (tree of heaven) in semiarid afforestation of Iran (Chitgar Forest Park, Tehran). For this purpose, sand, silt and clay ratios, bulk density, soil moisture, pH, electrical conductivity, phosphorus, potassium, magnesium, calcium, sodium, total soil N, and total carbon was measured. Our study highlighted the potential of the invasive trees by A. altissima, to alter soil properties along chronosequence. Almost all soil quality attributes showed a declining trend with stand age. A continuous decline in soil quality indicated that the present land management may not be sustainable. Therefore, an improved management practice is imperative to sustain soil quality and maintain long-term productivity of plantation forests. Thinning activity will be required to reduce the number of trees competing for the same nutrients especially in a older stand to protect forest soils.

A comparison of the effects of natural vegetation regrowth with a plantation scheme on soil structure in a geological hazard‐prone region

The effects of natural vegetation regrowth and plantation schemes on soil aggregate structure and total soil porosity were examined at a typical landslide hazard site in a semi‐humid region in northwest China. The schemes were started in 2008 using four plots, two of which were kept bare; in one natural local vegetation was allowed to grow and in the other planting was managed. Analysis of soil samples (0–100 cm) taken in 2016 indicated that the proportion of soil aggregates &lt;0.25 mm was 43.22 and 29.01% under natural vegetation and plantation, respectively, which was significantly greater than that in the plots kept bare (23%). Soil tensile stress increased from approximately 12 kPa in the bare plots to 18.34 and 16.45 kPa under natural vegetation and plantation, respectively. Total soil porosity, water retention and rate of infiltration increased, whereas bulk density decreased considerably, after 8 years under natural vegetation and plantation in comparison with those properties in the bare plots. Furthermore, natural vegetation had a greater effect than the plantation on soil structure in terms of aggregation and total porosity. The findings of this study provide some insight into the effects of native vegetation and a plantation on soil structure in semi‐humid regions as a prerequisite to the control of both soil erosion and slope stability in regions prone to seismic activity.Highlights Soil structure was analysed after 8 years of natural vegetation regrowth and plantation. Eight years of revegetation improved aggregation and total porosity compared with bare land. Natural vegetation affected soil structure more than the plantation did. Our results provide some insight into a prerequisite to control soil erosion and slope stability in unstable regions.

Numerical simulation of erosion for solid-liquid two-phase flow in u-tube

study predicts erosion damage caused by solid particles impact on the inner surface of u-tube. Based on finite volume method, study uses numerical simulation of Lagrange method to discuss different inlet velocity (from 2.5 m/s to 5.5 m/s) of fluid and mass flow rate discrete phase which affect the location and ratio of erosion. The results show that: with other parameters of fluid fixed, the mean erosion rate on the pipe wall increases from 8.72×10-9kg/m2·s to 7.3 × 10-8 kg/m2 ··s with a growth exponentially when the inlet velocity increases from 2.5m/s to 5.5m/s. With other parameters fixed, the facet average erosion rate increased from 1.85×108kg/m2·s to 8.68×10-8kg/m2·s with a liner growth. Moreover, the elbow of pipe appears obvious erosion phenomenon. Especially, due to centrifugal force, the erosion rate on lateral radius wall is significantly greater than the inner. The concentrated erosion region tends toward get wider as flow rate and mass flow rate of discrete phase increase.

Authigenic Titanium and Zirconium Minerals at the Verkhnekamskoe Salt Deposit

The salt-bearing and suprasalt units at the Verkhnekamskoe salt deposit contain newly formed Ti oxides and zircon. The minerals may have been produced at the decomposition of clay material and release of colloid Ti and Zr hydroxides during diagenesis, catagenesis, and supergenesis because of sulfate reduction and an acidic environment caused by Fe2+ oxidation in the sylvite and carnallite. Anatase was found in both the suprasalt units and the salt-bearing ones, whereas rutile occurs exclusively in the bottom part of the salt-bearing unit. The possible reasons for this distribution may have been intensification of the catagenetic transformations with depth and the composition of the coexisting sulfate or chloride brines, respectively. The anatase typically forms pinacoidal crystals, which give way to dipyramidal ones in the carnallite zone (whose solutions are the most acidic). The rutile shows twins of three types, whose origin was caused by the growth of the mineral in the fine-grained material of dehydrated Ti hydroxide colloid. The Ti oxides contain V, Cr, Zr, and (Al, Si, and Fe) admixtures, which reflect the geochemistry of the erosion regions which provided the aluminosilicate material.

Sediment yield at southwest Ethiopia's forest frontier

AbstractDeforestation is one of the major factors affecting soil erosion in tropical regions but to what extent does the crop growth in deforested areas protect the land from erosion? We evaluated the effect of deforestation on suspended sediment yield at the scale of zero‐order catchments by contrasting five paired small forest and cropland catchments at Ethiopia's southwestern forest frontier. Suspended sediment samples were collected from nine San Dimas flumes and one V‐notch weir installed in catchments draining the natural forest and cropland, at different altitudes. The suspended sediment data were collected from June 8 to October 30, 2013 and 2014. The suspended sediment yield of both land‐use types was strongly correlated with the corresponding runoff discharge. The results show that the average seasonal suspended sediment yield from cropland (17.0 ± 7.6 Mg ha−1) is four times higher than from the paired forests (4.0 ± 1.9 Mg ha−1). High sediment yields from forests are related to livestock grazing, but forests still have an important role in the protection of the surface soil from erosion at southwest Ethiopia's forest frontier. Land management in southwestern Ethiopia's highlands will need a strong change in paradigm, in which the overall belief in the recently imported mahrasha ard plough is abandoned, oxen and other cattle decreased in number and kept in homesteads, the forests being protected from human and livestock interferences and the open farmlands turned into agroforestry. Such an approach is still possible as all required elements are available in the landscape.

Optimum ridge width and suitable mulching material for sainfoin production with ridge–furrow rainwater harvesting in semiarid regions of China

Ridge-furrow rainwater harvesting (RFRH) with mulch offers farmers means to address drought, water loss, and soil erosion in arid and semiarid regions. Plastic film is widely used as a mulching material for RFRH; however, contamination of arable lands by its residual is a serious concern. We compared various mulches, including a biodegradable film for RFRH planted with sainfoin (Onobrychis viciifolia). A field study was conducted to (1) estimate runoff efficiency from three ridge widths using three different mulching materials; and (2) assess the effects of ridge widths and mulching materials on topsoil temperature, soil water storage, fodder yield, fodder nutrition, and water use efficiency (WUE) of RFRH planted with sainfoin, during 2015 and 2016. The predicted runoff efficiency for MCS30, MCS45, MCS60, BF30, BF45, BF60, PF30, PF45, and PF60 [MCS, BF, and PF are abbreviations for ridges with manually compacted soil, mulched with biodegradable film and with plastic film, respectively, subscripts 30, 45, and 60 refer to ridge widths (cm) all with 60 cm furrow width] was 9.9%, 22.2%, 24.7%, 85.3%, 88.8%, 92.7%, 85.9%, 89.7%, and 93.3%, respectively. The practice of RFRH, especially BF and PF, resulted in increased topsoil temperature at ridge tops and increased soil water content at furrow bottoms but decreased topsoil temperature at furrow bottoms. MCS decreased actual fodder yield, but BF and PF increased actual fodder yield. Compared to flat planting (FP), the decrease of actual fodder yield for MCS30, MCS45, and MCS60 was 7%, 15%, and 18%, respectively, for 2015 and 2016, but the increase of actual fodder yield for BF30, BF45, BF60, PF30, PF45, and PF60 was 10%, 8%, 6%, 15%, 13%, and 8%, respectively. Mean WUE for MCS, BF, and PF was 1.58, 1.64, and 1.70 times greater than that for FP, respectively. High soil water content and high soil temperature in RFRH, especially for BF and PF, resulted in increased crude protein and phosphorus content of the fodder produced but resulted in decreased acid detergent fiber and neutral detergent fiber content of fodder. Mean crude protein content for BF and PF was 1.25 and 1.30 times greater than that for FP, respectively, whereas phosphorus content for BF and PF was 1.37 and 1.32 times greater than that for FP. The optimum ridge width for BF was 35–36 cm, whereas for PF, it was 36–42 cm. The RFRH design should conserve water and improve fodder yields and quality.

Impacts of climate change and human activities on grassland vegetation variation in the Chinese Loess Plateau

China initiated the “Grain for Green Project” in 1999 to mitigate soil erosion. The vegetation cover of the Chinese Loess Plateau, one of the most erosive regions in the world, has been greatly increased. However, studies on quantitatively investigating the climate change and human activities on vegetation coverage change were rare. In this study, spatio-temporal changes in vegetation coverage were investigated using MODIS normalized difference vegetation index (NDVI) data over 2000–2016. And a new method was introduced using Net Primary Productivity (NPP) model and relationship between NPP and NDVI to quantitatively and spatially distinguish the NDVI affected by climate change and human activities. Results showed that mean NDVI value over 2009–2016 were 14.46% greater than that over 2000–2007. In order to quantify the contribution of climate change and human activities to vegetation change, an NPP model suitable for the grassland of the Chinese Loess Plateau was identified using biomass observations from field survey and literature. The NDVI affected by climate change (NDVIclimate) was estimated by the NPP model and the relationship between NPP and NDVI. And the NDVI affected by human activities (NDVIhuman) was calculated by actual NDVI minus NDVIclimate. Comparison of the two stages showed that human activities and climate change contributed 42.35% and 57.65% respectively to the ΔNDVI on grassland in the Loess Plateau. After analysis of numerous NDVIhuman related factors, the slopes restored by the “Grain for Green Project” was considered the main influence factor of human activities.