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To analyze the operation risk of check dams under extreme precipitation conditions, taking Ningxia area as an example, this paper carried out a risk assessment of check dams under extreme precipitation conditions in Ningxia through data collection, hydrological statistics, numerical simulation, and other methods. The conclusions are the following: (1) By the end of 2020, about 40% of the silt reservoir capacity of check dams in various water and soil conservation zones in Ningxia has been accumulated. During 1966–2020, the extreme precipitation and frequency of extreme precipitation in Ningxia increased while the intensity of extreme precipitation decreased. The extreme precipitation in Ningxia increased year by year and lasted longer. (2) Under two future scenarios of RCP4.5 (the full name of RCP is Representative Concentration Pathway) and RCP8.5, the extreme precipitation threshold in Ningxia is gradually decreasing from south to north. Extreme precipitation in the future will bring high risk to the operation of check dams in Ningxia. The results of this paper can provide a scientific basis for the operation and management of check dams in Ningxia. [ABSTRACT FROM AUTHOR]

Understanding the characteristics of the precipitation-use efficiency (PUE) of grassland ecosystems and its drivers is critical for predicting how ecosystem functions will respond to future climate change. In this study, we investigated several covarying biotic and abiotic factors (e.g., biomass, coverage, diversity, precipitation, temperature, and humid index (HI)) of 81 sites across a broad natural grassland gradient in the Loess Plateau of China to determine how PUE changes along a precipitation gradient and to assess the effects of biotic and abiotic factors on PUE. Our results showed that HI, below-ground biomass (BGB), vegetation coverage, and species diversity were the most important biotic factors in controlling PUE. HI had a higher positive indirect effect on PUE mainly through its influence on community characteristics. Our results suggest that precipitation and community characteristics are both important for the precipitation-use efficiency of natural grasslands across the arid and semiarid areas of the Loess Plateau. Additionally, improving the vegetation structure and increasing species diversity can help enhance the adaptability of grassland ecosystems to climate change. [ABSTRACT FROM AUTHOR]

Understanding the link between extreme precipitation and changes in runoff and sediment yield is of great significance for regional flood disaster response and soil and water conservation decision-making. This study investigated the spatial and temporal distribution of extreme precipitation (characterized by 10 extreme precipitation indices recommended by the Expert Team on Climate Change Detection and Indices) in the Toudaoguai–Longmen section of the middle Yellow River from 1960 to 2021 and quantified the effects of extreme precipitation on runoff and sediment yield based on the method of partial least squares regression (PLSR). The extreme precipitation index showed an obvious upward trend in the last 20 years, with the increases in the central and northern regions (upstream) being stronger than the increase in the southern region (downstream). However, the runoff and sediment yield decreased significantly due to the implementation of large-scale soil and water conservation measures on the Loess Plateau, with average rates of 94.7 million m3/a and 13.3 million t/a during 1960–2021, respectively. The change points of runoff and sediment yield change occurred in 1979. Compared with those in the period from 1960 to 1979, the reductions in runoff and sediment yield in the years 1980–2021 were 52.7% and 70.6%, respectively. Moreover, extreme precipitation contributed 35.3% and 6.2% to the reduction in runoff in the 1980–1999 and 2000–2021 periods, respectively, and contributed 84.3% and 40.0% to the reduction in sediment yield, respectively. It indicated that other factors (such as large-scale soil and water conservation construction) played main roles in the decrease in runoff and sediment yield in the study area in recent 20 years. [ABSTRACT FROM AUTHOR]

Precipitation and wind, as the main external erosion forces in wind–water erosion crisscross regions, have profound impacts on water and soil loss. Meanwhile, with the intensification of climate change and human activities, the variation characteristics and risks caused by erosion forces need to be reassessed. In this study, we explored the time-varying characteristics, differences in action period and spatial distribution, and temporal evolution of risk for the compound events of two erosion forces, including precipitation and wind, in the Pisha sandstone area, one of the most seriously eroding and difficult-to-control areas in the Loess Plateau. The results indicated that: (1) the stationarity of regional precipitation was not destroyed, but the mean change existed in the five subseries divided by the detected change points in wind; (2) wind acted earlier than precipitation and increased from southeast to northwest, while precipitation did the opposite; and (3) precipitation-led erosion has become the main erosion type in this area. The above results reveal the evolution and dominant types of regional external erosion forces in a changing environment and thus have implications for regional erosion studies and policy adjustments. [ABSTRACT FROM AUTHOR]

Over the past few decades, global vegetation cover has obviously changed, particularly in the Loess Plateau, due to vegetation restoration projects in China. This study focuses on the Pisha Sandstone area (PSA) and uses various statistical analysis methods to study the spatiotemporal changes in vegetation coverage (VEC) at different time scales. The effects of topographical and climatic factors on VEC were also quantitatively evaluated using the GeoDetector in the spatial distribution. The results of the study confirm that, on an annual scale, the area with a significant increase in VEC has reached 63.89% (p < 0.05). Change points were diagnosed to have occurred mainly between 2002 and 2012 at different time scales, with the percentage of significant change points in VEC accounting for more than 20% from April to October (p < 0.05). Temporal and spatial changes in precipitation mainly caused VEC changes. In 45.35% of the region, precipitation was significantly and positively correlated with VEC at an annual scale (p < 0.05). Moreover, VEC was most conducive to growth and increase at 1050–1500 m above sea level and 0–21° slope, respectively. In most areas, there was an enhanced interaction relationship between various factors on VEC. Converting farmland to forests in suitable areas, selecting appropriate tree species, and improving soil is conducive to ecological restoration in the PSA in the future. [ABSTRACT FROM AUTHOR]

The wind–water erosion crisscross region, where the topography is complicated, is the most severe area of soil erosion on the Loess Plateau. The wind and terrain both have an impact on the soil water erosion process. In order to evaluate the effects of sand cover on runoff and soil loss characteristics, a series of experiments was conducted in two contrasting treatments. One treatment was a bare loess soil slope serving as the control, and the others were sand-covered loess slopes with five different slopes. The results showed that the runoff time, total runoff yield, and total soil loss were different between the sand-covered slope and the loess slope on the slope of 15°. The sediment concentration of the sand-covered slope was significantly higher than that of the loess slope during the entire rainfall process (p < 0.05). The increase in the slope gradient shortened the surface runoff initiation times and enhanced the total runoff volume and soil loss. The total runoff volume and the total soil loss were 39.7 L and 44.3 kg, respectively, on the sand-covered slope of 10°. When the slope gradient increased from 10° to 30°, the total runoff volume and the total soil loss increased by 22.8 L and 42.8 kg, respectively, while the surface runoff initiation times shortened by 300 s. For the sand-covered slopes, the erosion processes appeared to be mainly dominated by sediment transport. The correlation between soil loss rates and slope gradients demonstrated the secondary polynomial function. In addition, the critical slope of sand-covered slopes was from approximately 23° to 28°. The proportion of sand cover and slope responsible for soil erosion was 3:1, which means the wind effect was more important than the terrace factor in terms of soil water erosion in the wind–water erosion crisscross region. The results provide a theoretical basis for soil erosion control in this area. [ABSTRACT FROM AUTHOR]

There is debating over the question of whether the large-scale 'Grain for Green' program on the Loess Plateau of China threatens regional food security. Self-sufficiency index and cropland pressure index were used to assess food security on the Loess Plateau after the implementation of revegetation program. The results showed that the 'Grain for Green' program initially had a considerable impact on regional food security, where grain yield fell from 1999 to 2001, resulting in a lower grain self-sufficiency and increased farmland stress. Subsequently, grain yield in this region increased due to the elevated agricultural material input and increased construction of terraces and check dams. The grain self-sufficiency index would have increased to 96.55% if there were improvements to the agricultural conditions, such as fertilization and irrigation, which would have resulted in an increase in the crop yield per unit of 20%. However, the grain self-sufficiency increased to 105.25% via the construction of terraces and check dams. Thus, the government should further expand the 'Grain for Green' program in coordination with improvements to the agricultural production conditions and the construction of terraces and check dams on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Ren, Z.; Feng Z.; Li, P.; Wang, D.; Cheng, S., and Gong J., 2017. Response of runoff and sediment yield from climate change in the Yanhe watershed, China. In: Zhi, Y. and Guido Aldana, P.A. (eds.), Sustainability of Water Resources and the Development of Coastal Environments: Select Proceedings from the 2016 International Conference on Water Resource and Environment (WRE2016). Journal of Coastal Research, Special Issue No. 80, pp. 30-35. Coconut Creek (Florida), ISSN 0749-0208. Changes in temperature and precipitation in the Loess Plateau, China have been studied for many years. The runoff and sediment yield in the Loess Plateau are sensitive to global climate change. Understanding the characteristics of runoff and sediment will be of great importance in the future. The Soil and Water Assessment Tool (SWAT) was used to simulate the runoff and the sediment yield in the Yanhe watershed, a typical water basin with soil erosion in the Loess Plateau. The resulting statistics of the SWAT simulation of the runoff and sediment yield were acceptable. The rainfall for the period from 2010 to 2099, as predicted by the Statistical Down Scaling Model (SDSM), was used to simulate the runoff and sediment yield in the future, using SWAT. Compared with the period from the 1980 to 2000, the annual precipitation increased by 9.2% to 16.4%. Under simulated future climate change, the annual runoff of the Yanhe watershed changes averaged −2.6% to 52.7%, compared with the baseline period. In the context of future climate change, in general, the runoff distribution was more even within the year when it increased significantly from March to May and decreased from July to August. The variations of the sediment yield for the watershed were −31.3% to 62.5% compare with the period from the 1980 to 2000. Overall, the trends of the sediment yield for the watershed were consistent with the runoff. [ABSTRACT FROM AUTHOR]

Soil salinization is currently a constraint on agriculture development in irrigated areas throughout the world. This study was conducted to examine the temporal stability and periodicity of groundwater electrical conductivity (EC) in irrigation districts. To accomplish this, 51 observation wells were selected for analysis of groundwater EC. Relative difference analysis and the non-parametric Spearman rank correlation test were used to check EC temporal stability, while the Morlet wavelet analysis was applied to measure the periodic variation of groundwater EC and groundwater level of high and low salinity wells. The mean groundwater EC of the 51 wells did not show an increasing trend over the entire measurement period, but demonstrated a moderate spatial variability, with coefficient of variation values ranging from 61 to 72%. The groundwater EC exhibited a strong temporal stability with Spearman correlation coefficients ranging from 0.81 to 0.98. The mean EC representative location in the study area was well 2, showing a good relationship between groundwater EC and groundwater level. Changes in groundwater EC were mainly affected by lateral groundwater recharge sources in small time scales. However, the groundwater EC and groundwater level always showed an obviously inverse phase with a large time scale due to precipitation effects. In conclusion, the groundwater EC, lateral recharge sources, and irrigation time should be fully considered in irrigation to avoid soil salinization. [ABSTRACT FROM AUTHOR]

• Sand cover delayed the runoff initiation times; increased soil loss significantly. • Sand cover changed runoff from infiltration- excess to saturation- excess. • Sand mulch on the slope accelerated rill formation and development. Soil erosion was severe in the wind-water erosion crisscross region of the northern Loess Plateau of China, where aeolian sand cover may enhance water erosion. In order to evaluate the effects of sand cover on runoff, soil loss and rill information, a series of rainfall simulation experiments was conducted in two contrasting treatments. One is a bare loess soil slope serving as a control, and another is a sand-covered loess slope (namely sand cover treatment). Nine simulated rains, 60 min each, were applied to each treatment in duplicates. The results showed that the runoff generation mechanism changed from infiltration-excess runoff in the control to subsurface saturation-excess runoff in the sand cover treatment. The runoff initiation was delayed about three folds in the sand cover treatment as compared to the control. Total runoff volumes and total soil loss in the sand cover treatment in each event were 1.1–1.2 times and 1.9–9.3 times those in the control treatment. A paired t -test showed that the runoff rates were greater in sand cover than in control in all events except for the last run at P < 0.05. The soil loss rates were greater in sand cover than in control for all events except the first rain at P < 0.05. Measured total rill length, width, and degree of rill dissection in the sand cover treatment were much greater than those in the control. The rill erosion of sand cover slope was dominated by the shallow and wider rills, while loess slope was dominated by the narrow and deeper rills. The results clearly indicated that a sand layer overlying a less pervious loess soil facilitated return flow and thus accelerated rill formation and development. This finding is in line with the common understanding that return flow in layered soil can promote rill formation and cause severe rill erosion, which is also important to understand the effect of wind-blown sand cover on water erosion in the wind-water erosion crisscross region. [ABSTRACT FROM AUTHOR]

Seasonal freeze-thaw processes have led to severe soil erosion globally. Slopes are particularly susceptible to changes in runoff, it can be useful to study soil erosion mechanisms. We conducted meltwater flow laboratory experiments to quantify the temporal and spatial distribution of hydraulic parameters on sandy slopes in relation to runoff and sediment yield under constant flow, different soil conditions (unfrozen slope: US; frozen slope: FS), and variable sand thickness. The results showed that sand can prolong initial runoff time, and US and FS have significantly different initial runoff times. There was a significant linear relationship between the cumulative runoff and the cumulative sediment yield. Additionally, hydrodynamic parameters of US and FS varied with time and spatially, as the distance between US and FS is linearly related to the top of the slope. We found that the main runoff flow pattern was composed of laminar flow and supercritical flow. There was a significant linear relationship between flow velocity and hydraulic parameters. The flow velocity is the best hydraulic parameter to simulate the trend of slope erosion process. This study can provide a scientific basis for a model of slope erosion during thawing for the Loess Plateau. [ABSTRACT FROM AUTHOR]

Soil properties are influenced by freeze-thaw, which in turn influences soil erosion. Despite this, only a few studies have investigated the impacts on soil hydrodynamic processes. The objective of this study was to evaluate the impact of soil freezing conditions on runoff, its energy consumption, and soil erosion. A total of 27 laboratory-concentrated meltwater flow experiments were performed to investigate the soil erosion rate, the runoff energy consumption, and the relationship between the soil erosion rate and runoff energy consumption by concentrated flow under combinations of three flow rates (1, 2, and 4 L/min) and three soil conditions (unfrozen, shallow-thawed, and frozen). The individual and combined effects of soil condition, flow rate, and runoff energy consumption on the soil erosion rate were analyzed. For the same flow rate, the shallow-thawed and frozen slope produced mean values of 3.08 and 4.53 times the average soil erosion rates compared to the unfrozen slope, respectively. The number of rills in the unfrozen soil slope were 4, 3, and 2 under the flow rate of 1, 2, and 4 L/min, respectively. The number of rills in the thawed-shallow and frozen soil slope were all 1 under the flow rate of 1, 2, and 4 L/min. The rill displayed disconnected distribution patterns on the unfrozen slope, but a connected rill occurred on the shallow-thawed and frozen slopes. The average rill width on unfrozen, thawed-shallow, and frozen soil slopes increased by 1.87 cm, 4.38 cm, and 1.68 cm as the flow rate increased from 1 L/min to 4 L/min. There was no significant difference in the rill length on the frozen slope under different flow rates (p > 0.05). The runoff energy consumption ranged from unfrozen > shallow-thawed > frozen slopes at the same flow rate. The soil erosion rate had a linear relationship with runoff energy consumption. The spatial distribution of the runoff energy implied that soil erosion was mainly sourced from the unfrozen down slope, shallow-thawed upper slope, and frozen full slope. [ABSTRACT FROM AUTHOR]

Abstract Revegetation and check dam construction are two widely applied soil erosion control measures on the Loess Plateau of China. They play important roles in sediment yield reduction. However, it remains unclear how these large-scale land-use changes and in-channel structures affect water yield and sediment load on the watershed scale. A combination of field work and modeling exercises were used to quantitatively assess the effects of land-use changes and check dam construction on hydrological processes in the Wuding River watershed. The study area suffered important land-use changes with increases in forestland and grassland, coupled with decreases in cropland, from 1980 to 2010. A large number of check dams were constructed from 1970 to 1980. Runoff and sediment yield in the watershed showed significant decreasing trends (P < 0.01), with change points occurring in the early 1970s. Human activity contributed to 75% and 89% of runoff and sediment changes, respectively. The simulations showed that in a scenario without check dams, runoff and sediment increased by 12% and 11.7%, respectively. Vegetation recovery reduced runoff and sediment yield. 'Grain for Green' resulted in decreasing runoff and sediment levels, and reforestation had more hydrological regulatory effects compared with scenarios involving the conversion of cropland to grassland. Moreover, the combination of revegetation and check dam construction had a greater impact on water yield and sediment transportation. Check dams provide short-term flood control and sediment reductions, whereas land-use changes are long-term sustained soil erosion control measures. It may be more efficient to combine check dam construction with revegetation strategies. Graphical abstract Unlabelled Image Highlights • Check dams decreased runoff and sediment yield by 12% and 11.7%, respectively. • Reforestation resulted in more runoff and sediment reduction than grassland. • Revegetation of slopes and check dam construction should be combined. [ABSTRACT FROM AUTHOR]

Abstract The seasonal freeze–thaw process affects soil water migration, which influence spring planting, especially in arid and semi-arid regions that cannot be irrigated on the Loess Plateau. This study was conducted to evaluate differences in the freeze–thaw process and water migration between dam farmland (DF) and slope farmland (SF). To accomplish this, two typical agricultural soils (DF and SF), soil water content (SWC) and soil temperature (ST) were monitored at different depths (15, 30, 60 and 90 cm), were investigated under freeze–thaw conditions from November 2015 to April 2016 in the Northwest China. The results showed that different freeze-thaw process between dam farmland (DF) and slope farmland (SF). The DF can keep soil water content resulting from longer frozen period. Thermal transmission between soil and air in SF is greater than that in DF. The SWC values in DF were higher than in SF at each depth layer under similar soil temperature. Migrated and incremental SWC in the DF is greater than that in SF during the freeze-thaw process. The initial SWC is the main impact on freeze–thaw process in this study. This research can provide useful information to guide the water management of seasonally frozen agricultural soil. Graphical abstract Unlabelled Image Highlights • The freeze-thaw process differed between dam farmland (DF) and slope farmland (SF). • The migration and increment of soil water content (SWC) in DF are larger than in SF. • The freeze–thaw process was mainly affected by initial SWC in this environment. [ABSTRACT FROM AUTHOR]

Abstract The sediment-reducing effect of check dams and the safety issues following dam breaks are long-standing concerns. This study analyzed the runoff change and sediment source during rainstorms in a small watershed using a multivariate mixed model and a comparative analysis of watersheds. The problem of sediment loss from dammed farmland following check dam break during rainstorms was evaluated. The results showed that the flood peak lag time (PLT) was significantly influenced by pre-soil moisture in cases of small amounts of rainfall but not during rainstorms. Ecological construction significantly reduced the linear correlation between rainfall and runoff modulus (RM). The reduction in sediment delivery modulus (SDM) due to the check dam was more significant than that in RM. The reduction in RM and SDM under rainstorm conditions were 16%–74% and 53%–93%, respectively. The contributions of inter-gully and gully lands to the sediment deposited in dammed farmland during a large rainstorm on July 26, 2017 were 38.07% and 61.93%, respectively. Soil erosion remained significant during large rainstorms. The increase in vegetation coverage on the hill slope increased the amount of sediment from gully lands. Check dam breaches have accounted for a loss of only 1.2% of the total area of the dammed farmland, and thus have not caused a large loss of sediment. However, breaches in them clearly increased the coefficient of variation of RM and SDM. Therefore, check dams have a critical effect on controlling sediment delivery at the watershed scale. Dam breaks do not result in a large percentage of sediment loss in the dammed farmland. Graphical abstract Unlabelled Image Highlights • We investigate sediment source during heavy rainstorms. • Assess the effects of soil and water conservation measures on runoff and sediment • Examined the changes to check dam breaches [ABSTRACT FROM AUTHOR]

Abstract Vegetation restoration, terrace and check dam construction are the major measures for soil and water conservation on the Loess Plateau. These effective measures of stabilizing soils have significant impacts on soil organic carbon (SOC) distribution. However, following ecological construction, whether the hilly watershed acts as a source or a sink of soil carbon is still unknown. To understand the impact of land-use changes combined with check dam construction on SOC distribution, 1060 soil samples were collected from a 100 cm soil profile across a watershed on the Loess Plateau. The soils in the 0–20 cm layer had a higher SOC concentration than those of the 20–40, 40–60, 60–80 and 80–100 cm layers. Forestland, shrubland and terrace had significant higher SOC concentrations in the 0–20 cm soil layer than that of sloping cropland and dammed farmland (p < 0.05). SOC densities (0–100 cm) in terrace, forestland, shrubland, grassland, sloping cropland and dammed farmland were 12.09, 11.99, 11.89, 11.77, 11.41 and 10.11 kg m−2, respectively. These estimations suggested that SOC was redistributed in the watershed through land-use changes. Topographical factors, including altitude, aspect and slope had impacts on SOC concentrations. The application of hydrological controls to hillslopes and along river channels should be considered when assessing carbon sequestration within the soil erosion subsystem. Graphical abstract Unlabelled Image Highlights • The revegetation and terrace on the slope increased SOC. • SOC distribution was effected by land use changes and check dam. • Topographical factors had impacts on SOC concentrations. [ABSTRACT FROM AUTHOR]

Abstract Surface water quality has a vital role in determining the ecological environment, public health, and social and economic development. This study analyzed the spatial and seasonal differences in surface water quality in the Dan River basin based on three monitoring sections over the period of 2009–2015. The main influencing factors and their contributions to water quality in different seasons were determined using statistical analysis, Hurst exponent and redundancy analysis. Results indicated that vegetation coverage in the Dan River basin increased substantially from 2009 to 2015, particularly forested land. Higher concentrations of major water pollution indicators were recorded in the downstream monitoring sites. Nitrate nitrogen (NN) and total phosphorus (TP) made the largest contributions to the pollution of water quality and indicated spatial and seasonal changes. Lower NN concentrations were more frequent during the summer, whereas TP concentrations were higher during the spring. Thus, the factor making the largest contribution to water quality varied with the season. The contribution of the normalized difference vegetation index (NDVI) to water quality gradually decreased from spring to winter, whereas contributions of land use to water quality gradually increased from spring to winter. Analyses of landscape metrics suggested that patch connectivity was the primary factor influencing water quality in the different seasons. Water level was the main hydrological parameter impacting stream water quality. These results suggested that seasonal differences in the major factors influencing water quality should be taken into account for effective water management. Highlights • The time series of vegetation coverage was a consistent sequence in Dan River. • Factors making the largest contribution to water quality varied with the season. • Patch connectivity was the primary factor influencing water quality. • Water level was the main hydrological parameter impacting stream water quality. [ABSTRACT FROM AUTHOR]

Soil respiration is a large carbon flux from terrestrial ecosystems to the atmosphere, and small variations in soil respiration can prominently influence the global carbon (C) cycle. The vegetation changes could directly affect soil respiration. The large-scale "Grain for Green" project carried out on the Loess Plateau, China has importantly affected the contribution of soil respiration to atmospheric carbon dioxide (CO 2). Therefore, it is important to study the effects of vegetation restoration on soil respiration. We selected four land-use types: crop, forest, shrub, and grassland in the Zhifanggou watershed to analyze variation in soil respiration during dry and rainy seasons. Furthermore, the source of CO 2 emissions from soil respiration was identified using isotopes. The results showed that soil respiration in the rainy season was significantly higher than that in the dry season (P <.05). Soil respiration in the dry season was as follows: shrubland (1.04 μmol m−2 s−1) > cropland (0.72 μmol m−2 s−1) > forestland (0.44 μmol m−2 s−1) > grassland (0.33 μmol m−2 s−1). However, grass and forestland had significantly higher soil respiration than shrub and cropland in the rainy season (P <.05). Roots were the main source of soil respiration in cropland, which contributed >70% of CO 2 emissions. Following revegetation, litter contributed more to soil respiration than roots or soil microorganisms at >68% of soil respiration. Our results provide a theoretical basis for assessing C balance in terrestrial ecosystems. Unlabelled Image • Soil respiration in the rainy season was higher than that in the dry season. • Vegetation restoration increased soil respiration in the rainy season. • Roots were the main source of soil respiration in cropland. • Litter was the most important source to soil respiration in the vegetation land. [ABSTRACT FROM AUTHOR]

• Difference erosion process of unfrozen, shallow-thawed and frozen soils under different meltwater flow. • The sediment yield capacity is not a constant value for the two kinds of soil structures. • Runoff energy consumption can well predict soil erosion rate. The processes of rill erosion and overland flow are significantly affected by freeze-thaw cycles. Meltwater concentrated flow laboratory experiments were carried out to assess the soil erosion of different frozen conditions based on the runoff energy consumption process which own to runoff energy against the sediment transportation and terrain evolution. The experiments were performed over frozen, shallow-thawed, and unfrozen soil-filled flumes under 1, 2, and 4 L/min flow rates with the temperature around 5 °C. The results imply that soil erosion became more severe with increasing flow rate. Variation rate of the soil erosion rate of frozen slope was highest under 1 and 2 L/min flow rates due to lower infiltration of water into soil. Variation in runoff energy consumption variation with flow time presented significant differences under unfrozen, shallow-thawed, and frozen slopes at equal runoff rate (p < 0.05). Compared with shallow-thawed and unfrozen slopes, frozen slope displayed the highest runoff energy consumption and sediment yield capacity at the equal flow rate. Sediment yield capacity was constant regardless of soil condition except in shallow-thawed soil. The sediment yield capacity under 4 L/min flow rate was different from that under 1 and 2 L/min flow rates for shallow-thawed slopes. Soil erosion rates were predictable using runoff energy consumption under one soil condition. The results of this research would provide specific implications about meltwater erosion process and hydrodynamic conditions for improving the erosion model. [ABSTRACT FROM AUTHOR]

Two contiguous watersheds in the Loess Plateau in China that differed in the way their vegetation had been restored-afforestation or natural revegetation-differed in their consumption of soil moisture: the afforested watershed consumed more soil moisture, although the difference was significant only in wet years. Yet, both the afforestation and natural revegetation did not induce the soil desiccation in the study area. In the afforested watershed, soil moisture was depleted even beyond a depth of 100 cm, whereas in the grassland (natural revegetation), the depletion was confined to a layer less than 60 cm deep. Rainfall in the growing season accounted for 46-60% of the variation in soil moisture in the 0-60 cm layer in the grassland, but only 22-39% of that in the forest land. Overall, afforestation is the better option for the Loess Plateau only in areas where the annual rainfall is more than 500 mm. In any attempt at revegetation, the choice of tree species and planting densities should match the carrying capacity of the region's water resources.