The Revised Universal Soil Loss Equation (RUSLE) was used in conjunction with geographic information system (GIS) mapping to determine the influence of land use and topography on soil erosion on the ...Loess Plateau during the period 2000 to 2010. The average soil erosion on the Loess Plateau was 15.2tha−1yr−1 in 2000–2010. Most of the Loess Plateau fell within the minimal and low erosion categories during 2000 to 2010. Forest, shrub and dense grassland provided the best protection from erosion, but the decadal trend of reduced soil erosion was greater for the lower vegetation cover of woodland and moderate and sparse grassland. Midslopes and valleys were the major topographical contributors to soil erosion. With slope gradient increased, soil erosion significantly increased under the same land use type, however, significant differences in soil erosion responding to slope gradients differed from land uses. The results indicate that the vegetation restoration as part of the Grain-to-Green Program on the Loess Plateau has been effective.
•Most of the Loess Plateau fell within the minimal and low erosion categories.•The general trend was a shift from relatively more severe erosion to slight.•The decadal trend of reduced soil erosion was greater for lower vegetation cover.•The middle slopes and the valleys were the major contributors to soil erosion.•The vegetation restoration on the Loess Plateau had an achievement.
In recent decades, extreme climatic events have been a major issue worldwide. Regional assessments on various climates and geographic regions are needed for understanding uncertainties in extreme ...events' responses to global warming. The objective of this study was to assess the annual and decadal trends in 12 extreme temperature and 10 extreme precipitation indices in terms of intensity, frequency, and duration over the Loess Plateau during 1960–2013. The results indicated that the regionally averaged trends in temperature extremes were consistent with global warming. The occurrence of warm extremes, including summer days (SU), tropical nights (TR), warm days (TX90), and nights (TN90) and a warm spell duration indicator (WSDI), increased by 2.76 (P<0.01), 1.24 (P<0.01), 2.60 (P=0.0003), 3.41 (P<0.01), and 0.68 (P=0.0041) days/decade during the period of 1960–2013, particularly, sharp increases in these indices occurred in 1985–2000. Over the same period, the occurrence of cold extremes, including frost days (FD), ice days (ID), cold days (TX10) and nights (TN10), and a cold spell duration indicator (CSDI) exhibited decreases of −3.22 (P<0.01), −2.21 (P=0.0028), −2.71 (P=0.0028), −4.31 (P<0.01), and −0.69 (P=0.0951) days/decade, respectively. Moreover, extreme warm events in most regions tended to increase while cold indices tended to decrease in the Loess Plateau, but the trend magnitudes of cold extremes were greater than those of warm extremes. The growing season (GSL) in the Loess Plateau was lengthened at a rate of 3.16days/decade (P<0.01). Diurnal temperature range (DTR) declined at a rate of −0.06°C /decade (P=0.0931). Regarding the precipitation indices, the annual total precipitation (PRCPTOT) showed no obvious trends (P=0.7828). The regionally averaged daily rainfall intensity (SDII) exhibited significant decreases (−0.14mm/day/decade, P=0.0158), whereas consecutive dry days (CDD) significantly increased (1.96days/decade, P=0.0001) during 1960–2013. Most of stations with significant changes in SDII and CDD occurred in central and southeastern Loess Plateau. However, the changes in days of erosive rainfall, heavy rain, rainstorm, maximum 5-day precipitation, and very-wet-day and extremely wet-day precipitation were not significant. Large-scale atmospheric circulation indices, such as the Western Pacific Subtropical High Intensity Index (WPSHII) and Arctic Oscillation (AO), strongly influences warm/cold extremes and contributes significantly to climate changes in the Loess Plateau. The enhanced geopotential height over the Eurasian continent and increase in water vapor divergence in the rainy season have contributed to the changes of the rapid warming and consecutive drying in the Loess Plateau.
•Extreme temperature indices exhibited trends consistent with global warming.•Warm-event indices significantly increased, whereas cold-event indices decreased.•The growing season was lengthened in the Loess Plateau.•The daily rainfall intensity exhibited a significant decrease over time.
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•A connectivity index was coupled with a soil erosion model to estimate sediment yield.•Afforestation led to evident decreases in both the connectivity and the sediment delivery ...ratio.•The modeled sediment yield showed a 60.7% reduction due to changes in land use and check dams.
The hydrological connectivity on the Loess Plateau has been greatly altered by soil and water conservation measures in the past six decades, leading to significant reduction in sediment load. Nevertheless, how these measures affect sediment transport at the catchment scale remains unclear. This study coupled an index of connectivity (IC) with the Revised Universal Soil Loss Equation (RUSLE) model to estimate the sediment yield in the Yanhe catchment (7,725 km2). The model was used to assess the impacts of land use changes and check dam construction on sediment delivery. The land use maps showed increasing grassland (10.3%) and decreasing arable land (12.3%) from 1990 to 2010. The ranges of IC between the two land use scenarios showed significant changes with an average of 0.3 in 1990 and −0.5 in 2010. Land use changes resulted in average sediment delivery ratio decreasing from 0.39 in 1990 to 0.30 in 2010. The model was calibrated by annual sediment load at a gauging station, covering 5,852 km2 of the catchment and by sedimentation rates behind check dams in a representative sub-catchment. Measured and simulated sediment load showed consistent agreement, suggesting acceptable model performance. An approximately 60.7% reduction in sediment yield was attributed to land use changes and increasing check dams′ construction from 1990 to 2010. This study provided a good example of combining the IC with a soil erosion model to identify spatial patterns and temporal variations in sediment yield due to soil conservation measures.
The Loess Plateau suffers from severe soil erosion that leads to a series of ecological and economic problems such as reduced land productivity, exacerbated rural poverty, decreased biodiversity and ...sedimentation of the riverbed in the lower reaches of the Yellow River. Soil erosion models are commonly used on the Loess Plateau to help target sustainable land management strategies to control soil erosion. In this study, we compared eleven soil erosion models that were previously used on the Loess Plateau. We studied their prediction accuracy, process representation, data and calibration requirements, and potential application in scenario studies. The selected models consisted of a broad range of model types, structures and scales. The comparison showed that process-based and empirical models did not necessarily yield more accurate results over one another for the Loess Plateau. Among the process-based models, Si’ model, WEPP and MMF had the highest prediction accuracy. However, some of the selected models were tested with total sediment load while others were tested with suspended sediment load (i.e. bedload is not included), which is subject to several drawbacks. Research questions that each of the models can address on the Loess Plateau were suggested. Further improvement of soil erosion models for the Loess Plateau should concentrate on enhancing the quality of data for model implementation and testing, incorporating key processes into process-based models according to their aims and scales, comparing models that address the same research questions, and implementing internal and spatial model testing.
•The effects of land use intensified from summits to slope areas to gullies.•The effects of land use extended from 20cm on the summit to 80cm in the gullies.•Significant interactions between land use ...and topography on the SOC were observed.•Land use and topography were key predictors of the SOC spatial distribution.
Land use and topography are two primary factors that affect the spatial distribution of soil organic carbon (SOC) at the watershed scale, particularly in areas of multiple land uses and complex topography on the Loess Plateau. The General Linear Model (GLM) combined with Duncan’s Multiple Range Test (DMRT) were used to conduct variance tests and evaluate the effects of topography (summit, sloping areas and gullies), land use (farmland, orchard, grassland, shrubland and woodland), and their interactions on the vertical and horizontal distributions of SOC at soil depths of 0–10, 10–20, 20–40, 40–60, 60–80 and 80–100cm. The effects of land use intensified from the summits to the slope areas to the gullies. The SOC concentrations throughout the 100cm-thick soil profiles in farmland in slope areas and gullies were, respectively, 45.4% (P<0.0001) and 55.2% (P<0.0001) greater than those on the summits (3.1gkg−1). In slope areas, the SOC concentrations in shrubland and grassland exceeded those in farmland (4.5gkg−1) by 52.1% (P<0.0001) and 15.8%, respectively. In addition, in the gullies, the mean SOC concentrations in shrubland and grassland exceeded those in farmland (4.8gkg−1) by 80.6% (P<0.0001) and 50.7% (P=0.0039), respectively. The SOC concentrations in areas of semi-shaded slope aspects were greater than those in areas of semi-sunny aspects. The enhanced effect of topographic position on SOC may be attributed to the vegetation and the soil conditions associated with the land uses and to the interactions between these variables at the watershed scale. These results could enhance understanding of the effects of environmental factors and their interaction on the spatial variation of SOC in regions with complex topography. These conclusions could have important implications for ecosystem recovery through rational land use changes in the ecologically fragile areas of the Loess Plateau and for improving the accuracy of prediction of SOC in regions of complex topography and land use on the Loess Plateau.
Large-scale sediment control efforts on the Loess Plateau of China and resulting reductions in sediment yield have been documented. However, it remains unclear how these control works affect the soil ...erosion rates and sediment loads at the catchment scale. A combination of field work and modeling exercises was used to examine the effects of land use changes and check dams on the variation of sediment yield at the catchment scale. The Huangfuchuan catchment was selected as a case study. The sediment distributed delivery (SEDD) model was calibrated using both observed sediment load data and sedimentation rates derived from check dams. The study catchment suffered important land use changes with increasing grassland and decreasing bare land, sandy area and arable land from 1990 to 2006. By 2009, 502 check dams with a total storage capacity of 571Mm3 had been built in the study area. Relatively good agreement can be seen between observations and model simulation results. Model applications showed that in a scenario without check dams, the land use changes between 1990 and 2006 caused a remarkable reduction of 31.4% in sediment yield. The check dams without land use changes with respect to the 1990 scenario reduced 51.9% of the sediment yield in the study area. The combination of land uses and check dam construction in 2006 reduced the sediment yield by approximately 80%. Our results indicate that check dams are efficient sediment control measures; however, the accumulation of sediment in check dams may create costly problems in the operation of dams and failures because of their short lives. Therefore, sustainable solutions are needed for sediment management in the check dams, such as sediment pass-through, flushing, or mechanical removal, and a reasonable construction plan is also needed for flood control.
•We found increasing grassland, decreasing bare land and sandy area within 1990–2006.•The catchment has 502 check dams with total volume of 571Mm3 built by 2009.•Land use changes and check dams in 2006 reduced the sediment yield nearly by 80%.•Check dams are efficient but not sustainable measures for sediment control.
Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and ...undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.
Hydrological regimes in the Yellow River have changed significantly because of climate change and intensive human interventions. These changes present severe challenges to water resource utilization ...and ecological development. Variation of run‐off, suspended sediment load (SSL), and eight precipitation indices (P1: 0–12 mm·day−1, P12: 12–25 mm·day−1, P25: 25–50 mm·day−1, P50: P ≥ 50 mm·day−1 and corresponding rainfall day: Pd1, Pd12, Pd25, Pd50 day year−1) in three critical parts of the Yellow River basin (source region: SRYRB, upper reaches: URYRB, middle reaches: MRYRB) were investigated for the period from 1960 to 2015. The results show that run‐off and SSL significantly decreased (P < 0.01) in the URYRB and the MRYRB, whereas their decline in the SRYRB was insignificant (P > 0.05). Moreover, run‐off in the URYRB had one change point in 1987, and SSL in the URYRB as well as run‐off and SSL in the MRYRB had two change points (in the 1970s and the 1990s). Over the same period, only Pd1 and Pd12 in the SRYRB showed significant increasing trends, and an abrupt change appeared in 1981. The optimal precipitation indices for assessing the effects of precipitation on run‐off and SSL in the URYRB and MRYRB were Pd50 and P12, respectively. A double‐mass curve analysis showed that precipitation and human activities contributed to approximately 20% and 80% of the reduction in run‐off, respectively, for both the SRYRB and the MRYRB. However, the contribution rate of precipitation and human activities on SSL reduction was approximately 40% and 60% in the URYRB and 5% and 95% in the MRYRB, respectively. Human activities, primarily soil and water conservation measures and water extraction (diversion), were the main factors (>50%) that reduced the run‐off. However, the dominant driving factors for SSL reduction were soil and water conservation measures and reservoir interception, for which the contribution rate was higher than 70% in the MRYRB. This work strengthens the understanding of hydrological responses to precipitation change and provides a useful reference for regional water resource utilization.
Surface water bodies exhibit dynamic characteristics, undergoing variations in size, shape, and flow patterns over time due to numerous natural and human factors. The monitoring of spatial-temporal ...changes in surface water bodies is crucial for the sustainable development and efficient utilization of water resources. In this study, Landsat series images on the Google Earth Engine (GEE) platform, along with the HydroLAKES and China Reservoir datasets, were utilized to establish an extraction process for surface water bodies from 1986 to 2021 in the Yellow River Basin (YRB). The study aims to investigate the dynamics of surface water bodies and the driving factors within the YRB. The findings reveal an overall expansion tendency of surface water bodies in the YRB between 1986 and 2021. In the YRB, the total area of surface water bodies, natural lakes, and artificial reservoirs increased by 2983.8 km2 (40.4%), 281.1 km2 (11.5%), and 1017.6 km2 (101.7%), respectively. A total of 102 natural lakes expanded, while 23 shrank. Regarding artificial reservoirs, 204 expanded, and 77 shrank. The factors that contributed most to the increase in the surface water bodies were increasing precipitation and reservoir construction, whose contribution rates could reach 47% and 32.6%, respectively. Additionally, the rising temperatures melted permafrost, ice, and snow, positively correlating with water expansion in the upper reaches of the YRB, particularly natural lakes.
•Water conservation capacity showed an insignificant increasing trend.•Landscape patterns tend to be fragmented and diversified.•Increased landscape fragmentation and diversity was conducive to the ...improvement of water conservation.•Vegetation coverage played an important promoting effect on water conservation.
With the accelerating changes of land use/cover caused by natural and human factors, landscape pattern has undergone significant changes. Given the scarcity of water resources and the degradation of ecological functions in arid and semi-arid regions of China, it is necessary to analyze the impact of landscape pattern changes on water conservation. Taking the Wei River Basin (WRB) as the research area, based on water balance equations, FRAGSTATS 4.2 software, and correlation analysis method, this study explored the spatiotemporal distribution characteristics of water conservation and landscape pattern in the WRB from 1990 to 2020, as well as the correlations between the two. The results showed that from 1990 to 2020: (1) the water conservation capacity (WCC) showed no insignificant change trend (P > 0.05) in sub water basins as well as the entire WRB, and it presented a spatial distribution pattern of more in the south and west, and less in the north and east; (2) the landscape diversity and fragmentation of the WRB have increased, and the patch shapes tended to be complex, while connectivity and agglomeration between patches decreased; (3) The WCC had significant negative correlations with the Contagion Index (CONTAG), connectivity index (COHESION), and largest patch index (LPI), while had significant positive correlations with landscape shape index (LSI), Shannon diversity index (SHDI), and separation index (SPLIT), indicating that the increase of landscape fragmentation and diversity was conducive to the improvement of WCC. In the process of ecological landscape planning and optimization, the fragmentation degree of landscape can be appropriately increased. (4) Vegetated grassland, forestland, and farmland were the main sources of WCC, with average WCC values of 81.90, 68.04, and 8.72 mm, respectively. NDVI of the watershed increased significantly (P < 0.01) during the research period and showed a significant positive correlation with WCC, indicating the promoting effect of increasing vegetation coverage on WCC. Relevant results may provide referential information for ecological restoration and optimization of landscape pattern in arid/semiarid regions.
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