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Elucidating the mechanism of soil erosion caused by extreme rainstorms could improve agroecosystems' resilience to the extreme climate. However, less attention has been paid to the regional difference of soil erosion during extreme rainstorms through multiple field investigations. Using six field surveys of extreme rainstorms, soil erosion and its driving mechanism were investigated on farmland in the Loess area and the Rocky mountain area. Conclusions are as follows: (1) Farmland was severely eroded in comparison with abandoned land and forest–grass land. The erosion modulus of farmland in the Loess area (51 606.51 t/km2) was greater than that in the Rocky mountain area (2582.75 t/km2). (2) In both the Loess area and the Rocky mountain area, the main erosion types on sloped cropland and terraced land were rills/gullies and embankment failure, respectively. Terracing is an appropriate measure that can effectively control farmland erosion in rainstorm events. (3) Concentrated flow is a major driver of soil erosion, with nearly all rills/gullies occurring in the flow paths. Drainage measures can prevent the formation of concentrated flow, weakening rills/gullies erosion in farmland. (4) Building bio‐embankment, planting high‐coverage crops, and implementing local protection measures could reduce the farmland erosion influenced by extremely heavy rainfall. Combining drainage and agronomic measures is the common strategy to combat extreme rainstorm events for reducing farmland erosion in the two regions. These results can be applied to improve the ability of agricultural systems to cope with extreme rainstorms. [ABSTRACT FROM AUTHOR]

The deteriorating soil carbon, nutrients, and microbial habitat pose a serious threat to crop production. However, the effects of long‐term cultivation with soil erosion on soil carbon, nitrogen, and bacterial communities remain poorly understood. Consequently, this study aims to explore the changes in these soil indicators in the last 110 years and their responses to soil erosion. Luvic Phaeozems in hillslope and Haplic Phaeozems in flat were sampled along 113‐ and 67‐year cultivation chronosequences. The soil organic carbon (SOC), total nitrogen (TN), soil loss rate, the soil bacterial community, and so on were respectively determined using the Walkley–Black, the Kjeldahl, nuclide tracing method, and 16S rRNA amplicon sequencing methods. The comparisons of SOC, TN, and soil bacterial community between Luvic Phaeozems and Haplic Phaeozems were used to differentiate their responses to the soil erosion intensity. The results indicated that SOC and TN decreased negatively and exponentially during long‐term cultivation and took longer to regain stability in Luvic Phaeozems than in Haplic Phaeozems (e.g., SOC: from 55.77 to 23.11 g kg−1 after 152 years vs. from 91.83 to 34.24 g kg−1 after 32 years). The bacterial community transitioned into Proteobacteria‐dominant communities and the quantity of carbon‐fixing and nitrogen‐fixing functional groups decreased. These shifts were mainly driven by the SOC and TN contents (40%) and their loss ratios (44%). In conclusion, soil erosion leads to more severe SOC and TN loss on hillslope than flat under long‐term improper cultivation, ultimately endangering soil bacterial ecological functions, which has important implications for effective soil erosion control and encouraging conservation tillage in this food‐producing region. [ABSTRACT FROM AUTHOR]

Soil erosion is a global environmental problem. The rapid monitoring of the coverage changes in and spatial patterns of photosynthetic vegetation (PV) and non-photosynthetic vegetation (NPV) at regional scales can help improve the accuracy of soil erosion evaluations. Three deep learning semantic segmentation models, DeepLabV3+, PSPNet, and U-Net, are often used to extract features from unmanned aerial vehicle (UAV) images; however, their extraction processes are highly dependent on the assignment of massive data labels, which greatly limits their applicability. At the same time, numerous shadows are present in UAV images. It is not clear whether the shaded features can be further classified, nor how much accuracy can be achieved. This study took the Mu Us Desert in northern China as an example with which to explore the feasibility and efficiency of shadow-sensitive PV/NPV classification using the three models. Using the object-oriented classification technique alongside manual correction, 728 labels were produced for deep learning PV/NVP semantic segmentation. ResNet 50 was selected as the backbone network with which to train the sample data. Three models were used in the study; the overall accuracy (OA), the kappa coefficient, and the orthogonal statistic were applied to evaluate their accuracy and efficiency. The results showed that, for six characteristics, the three models achieved OAs of 88.3–91.9% and kappa coefficients of 0.81–0.87. The DeepLabV3+ model was superior, and its accuracy for PV and bare soil (BS) under light conditions exceeded 95%; for the three categories of PV/NPV/BS, it achieved an OA of 94.3% and a kappa coefficient of 0.90, performing slightly better (by ~2.6% (OA) and ~0.05 (kappa coefficient)) than the other two models. The DeepLabV3+ model and corresponding labels were tested in other sites for the same types of features: it achieved OAs of 93.9–95.9% and kappa coefficients of 0.88–0.92. Compared with traditional machine learning methods, such as random forest, the proposed method not only offers a marked improvement in classification accuracy but also realizes the semiautomatic extraction of PV/NPV areas. The results will be useful for land-use planning and land resource management in the areas. [ABSTRACT FROM AUTHOR]

Rainfall erosivity quantifies the effect of rainfall and runoff on the rate of soil loss. Maps of rainfall erosivity are needed for erosion assessment using the Universal Soil Loss Equation (USLE) and its successors. To improve erosivity maps that are currently available, hourly and daily rainfall data from 2381 stations for the period 1951–2018 were used to generate new R -factor and 1-in-10-year event EI 30 maps for mainland China (available at 10.12275/bnu.clicia.rainfallerosivity.CN.001; Yue et al., 2020b). One-minute rainfall data from 62 stations, of which 18 had a record length > 29 years, were used to compute the "true" rainfall erosivity against which the new R -factor and 1-in-10-year EI 30 maps were assessed to quantify the improvement over the existing maps through cross-validation. The results showed that (1) existing maps underestimated erosivity for most of the south-eastern part of China and overestimated for most of the western region; (2) the new R -factor map generated in this study had a median absolute relative error of 16 % for the western region, compared to 162 % for the existing map, and 18 % for the rest of China. The new 1-in-10-year EI 30 map had a median absolute relative error of 14 % for the central and eastern regions of China, compared to 21 % for the existing map (map accuracy was not evaluated for the western region where the 1 min data were limited); (3) the R -factor map was improved mainly for the western region, because of an increase in the number of stations from 87 to 150 and temporal resolution from daily to hourly; (4) the benefit of increased station density for erosivity mapping is limited once the station density reached about 1 station per 10 000 km 2. [ABSTRACT FROM AUTHOR]

Hepatitis E, a significant global public health issue in China, is caused by sporadic infections with regional hepatitis E virus (HEV) genotypes 1, 3, and 4. To date, most immunoassays currently used to test human sera for the presence of anti-HEV antibodies cannot identify HEV at the genotype level. However, such information would be useful for identifying the source of infecting virus. Therefore, here we describe the development of a competitive enzyme-linked immunosorbent assay (ELISA) for detecting anti-genotype 1 HEV antibodies in human sera. Using recombinant genotype 1 HEV ORF3 protein as immunogen, traditional hybridoma technology was employed to generate seven monoclonal antibodies (mAbs), of which two mAbs specifically reacted with the immunogen. One of these two mAbs, 1D2, was labeled with horseradish peroxidase (HRP) for use in competitive ELISA (cELISA). After cELISA optimization using a checkerboard assay design, the amount of ORF3SAR−55 as coating antigen (100 ng/well), HRP-1D2 mAb concentration (1 μg/mL), and test serum dilution (1:10) were selected and a result ≥ 19.5 was used as the cutoff for a positive result. Importantly, cross-genotype cELISA results indicated that the cELISA could not detect anti-genotype 3 rabbit and 4 swine HEV antibodies. Moreover, human sera confirmed as negative for anti-HEV antibodies using the commercial ELISA kit were all negative via cELISA. However, because the commercial ELISA kit detects anti-all genotypes HEV antibodies and the cELISA only detects anti-genotype 1 HEV antibodies, the consistence rate of two assays detecting positive sera is low. In summary, here a cELISA for detecting anti-genotype 1 HEV antibodies was developed for use in epidemiological investigations of genotype 1 HEV infections in humans. Key points: • Seven mAbs were produced using genotype 1 HEV ORF3 protein as immunogen. • One mAb that specifically bound to genotype 1 HEV ORF3 protein was selected and labeled for use in a cELISA to detect anti-genotype 1 HEV antibodies. • The competitive ELISA developed here will aid clinical diagnosis of HEV infections and will be useful for large-scale serological testing of genotype 1 HEV infections in humans. [ABSTRACT FROM AUTHOR]

Rainfall erosivity represents the effect of rainfall and runoff on the average rate of soil erosion. Maps of rainfall erosivity are indispensable for soil erosion assessment using the Universal Soil Loss Equation (USLE) and its successors. To improve current erosivity maps based on daily rainfall data for mainland China, hourly rainfall data from 2381 stations for the period 1951-2018 were collected to generate the R factor and the 1-in-10-year EI30 maps (available at https://dx.doi.org/10.12275/bnu.clicia.rainfallerosivity.CN.001; Yue et al., 2020). Rainfall data at 1-min intervals from 62 stations (18 stations) were collected to calculate rainfall erosivities as true values to evaluate the improvement of the new R factor map (1-in-10-year EI30 map) from the current maps. Both the R factor and 1-in-10-year EI30 decreased from the southeastern to the northwestern, ranging from 0 to 25300 MJ mm ha-1 h-1 a-1 for the R factor and 0 to 11246 MJ mm ha-1 h-1 for the 1-in-10-year EI30. New maps indicated current maps existed an underestimation for most of the southeastern areas and an overestimation for most of the middle and western areas. Comparing with the current maps, the R factor map generated in this study improved the accuracy from 19.4 % to 15.9 % in the mid-western and eastern regions, from 45.2 % to 21.6 % in the western region, and the 1-in-10-year EI30 map in the mid-western and eastern regions improved the accuracy from 21.7 % to 13.0 %. The improvement of the new R factor map can be mainly contributed to the increase of data resolution from daily data to hourly data, whereas that of new 1-in-10-year EI30 map to the increase of the number of stations from 744 to 2381. The effect of increasing the number of stations to improve the interpolation seems to be not very obvious when the station density was denser than about 10 · 103 km2 1 station. [ABSTRACT FROM AUTHOR]

The cover‐management factor (C‐factor) is used in the revised universal soil loss equation to represent the effect of vegetation cover and its management practices on hillslope erosion. Remote sensing has been widely used to estimate vegetation cover and the C‐factor, but most previous studies only used the photosynthetic vegetation (PV) or green vegetation indices (VI, e.g., normalized difference VI) for estimating the C‐factor and the important non‐PV (NPV) component was often ignored. In this study, we developed a new technique to estimate monthly time‐series C‐factor using the fractional vegetation cover (FVC) including both PV and NPV, and weighted by monthly rainfall erosivity ratio. The monthly FVC was derived from the moderate resolution imaging spectroradiometer and LANDSAT data with field validation. We conducted the case‐study over China's Loess Plateau and analysed the spatiotemporal variations of FVC and the C‐factor and their impacts on erosion over the Plateau. Our study reveals a significant increase in total vegetation cover (TC) from 56 to 76.8%, with a mean of 71.2%, resulting in about 20% decrease in the C‐factor and erosion risk during the 17‐year period. Our method has an advantage in estimating the C‐factor from TC at a monthly scale providing a basis for continuously and consistently monitoring of vegetation cover, erosion risk and climate impacts. [ABSTRACT FROM AUTHOR]

The natural environment provides material essentials for human survival and development. The characteristics, processes, regional differentiation and forcing mechanisms of the elements of the natural environment (e.g. geomorphology, climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective. [ABSTRACT FROM AUTHOR]

Soil erosion is one of the most significant environmental problems in China. From 2010 to 2012, the fourth national census for soil erosion sampled 32 364 PSUs (Primary Sampling Units, small watersheds) with the areas of 0.2-3 km2. Land use and soil erosion controlling factors including rainfall erosivity, soil erodibility, slope length, slope steepness, biological practice, engineering practice, and tillage practice for the PSUs were surveyed, and the soil loss rate for each land use in the PSUs was estimated using an empirical model, the Chinese Soil Loss Equation (CSLE). Though the information collected from the sample units can be aggregated to estimate soil erosion conditions on a large scale; the problem of estimating soil erosion condition on a regional scale has not been addressed well. The aim of this study is to introduce a new model-based regional soil erosion assessment method combining a sample survey and geostatistics. We compared seven spatial interpolation models based on the bivariate penalized spline over triangulation (BPST) method to generate a regional soil erosion assessment from the PSUs. Shaanxi Province (3116 PSUs) in China was selected for the comparison and assessment as it is one of the areas with the most serious erosion problem. Ten-fold cross-validation based on the PSU data showed the model assisted by the land use, rainfall erosivity factor (R), soil erodibility factor (K), slope steepness factor (S), and slope length factor (L) derived from a 1 : 10 000 topography map is the best one, with the model efficiency coefficient (ME) being 0.75 and the MSE being 55.8% of that for the model assisted by the land use alone. Among four erosion factors as the covariates, the S factor contributed the most information, followed by K and L factors, and R factor made almost no contribution to the spatial estimation of soil loss. The LS factor derived from 30 or 90m Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data worsened the estimation when used as the covariates for the interpolation of soil loss. Due to the unavailability of a 1 : 10 000 topography map for the entire area in this study, the model assisted by the land use, R, and K factors, with a resolution of 250 m, was used to generate the regional assessment of the soil erosion for Shaanxi Province. It demonstrated that 54.3% of total land in Shaanxi Province had annual soil loss equal to or greater than 5 t ha-1 yr-1. High (20-40 t ha-1 yr-1), severe (40-80 t ha-1 yr-1), and extreme (>80 t ha-1 yr-1) erosion occupied 14.0% of the total land. The dry land and irrigated land, forest, shrubland, and grassland in Shaanxi Province had mean soil loss rates of 21.77, 3.51, 10.00, and 7.27 t ha-1 yr-1, respectively. Annual soil loss was about 207.3 Mt in Shaanxi Province, with 68.9% of soil loss originating from the farmlands and grasslands in Yan'an and Yulin districts in the northern Loess Plateau region and Ankang and Hanzhong districts in the southern Qingba mountainous region. This methodology provides a more accurate regional soil erosion assessment and can help policymakers to take effective measures to mediate soil erosion risks. [ABSTRACT FROM AUTHOR]

Conventional tillage refers to the tillage process, especially the spring and autumn plowing process in which all the soil surface layer is disturbed, generally tilling approximately 20 cm deep. Conventional tillage is still widely used in sloping land, which leads to serious soil erosion and land degradation. The effect of tillage on soil erosion is defined by Tillage factor (T) in the model. The purpose of this study is to analyze the effect of conventional tillage on soil erosion and to calculate the value of the conventional tillage Factor T. The values of the conventional tillage factor (T value) were calculated for different soil and water conservation zones in China by collecting published literature and plot measurements from unpublished monitoring sites. The results showed that (1) the tillage factors of conventional tillage in China ranged from 0.27 to 0.55, with the largest being the North earth-stony region, the smallest being the Qinghai-Tibet plateau region, and the other six regions, namely, the Northeastern mollisol, the Northern wind erosion, the Northwest Loess Plateau, the South red soil, the Southwestern purple soil and the Southwestern karst region, were 0.34, 0.28, 0.53, 0.37, 0.35 and 0.29, respectively. In the regional soil erosion evaluation, the values can be taken by each of the eight main erosion type regions. (2) In the water erosion area except for the northeast, there is an obvious north south difference in the distribution of the T value, showing a decreasing trend from north to south. In practical use, the T value of the corresponding latitude area can be determined according to the Equation T = 0.2351φ- 0.02225, where φ is the latitude (°). (3) The T values of contour tillage, no-till, and monopoly tillage measures are significantly lower than the T values of conventional tillage, which have significant soil and water conservation benefits. The study initially determined the conventional tillage T values for each water conservation subzone, which can provide basic parameters for soil loss prediction on sloping land. • The t values of 8 subzones are calculated, which can be used in the actual survey. • A formula for calculating t-values is proposed, which can be used for unmeasured areas. • Conventional tillage can reduce soil loss and must be assigned a reasonable value. [ABSTRACT FROM AUTHOR]

To determine the relationship between decreased egg production and avian HEV infection, thirty healthy 23-week-old Hy-Line Variety Brown layer hens were randomly divided into 3 groups with 10 hens per group. Next, a genotype 3 avian HEV strain from China was used to inoculate laying hens via oronasal or intravenous routes using a 50% chicken infectious dose of 500. All hens were necropsied at 14 weeks postinoculation (wpi). Fecal virus shedding, viremia, seroconversion, serum alanine aminotransferase (ALT) increases and liver lesions showed that after intravenous (i.v.) and oronasal inoculation, the laying hens were successfully infected. Compared with the uninoculated group, the i.v. and oronasally inoculated groups exhibited egg production decreases at 1 wpi and 2 wpi, reaching peak production at 3 wpi and 8 wpi, respectively. In both groups, decreased production was evident for 12 weeks and overall decreases ranged from 10% to 30%. In addition, in the 7 field layer farms exhibiting decreased egg production, vaccination regimens had been completed against Newcastle disease, infectious bronchitis, avian influenza H9N2 and H5N1 and egg drop syndrome virus. However, circulating avian HEV was confirmed on these farms using tests to detect avian HEV IgG antibodies and RNA. Therefore, the experimental and field data indicate that avian HEV infection acting alone could account for observed decreases in egg production in laying hens. [ABSTRACT FROM AUTHOR]

The topography (slope gradient and slope length) has an important effect on soil erosion by water. Slope gradient and slope length factor are the parameters of the universal soil loss equation that is commonly used to predict soil erosion. These factors are usually extracted from the digital elevation model (DEM). Thus the DEM grid size will influence topographic factors and therefore soil loss calculation. The purpose of this study was to investigate the effect of DEM grid size on the topographic factors and therefore soil loss prediction on a typical watershed in northeast of China. The site for the case study was Dontaigou watershed which is located at Huairou district, Beijing, China. Contour lines of 2 m interval digitized from 1:2,000 scale of topographic maps were used to generate DEM with grid size of 2 m. The DEMs with grid sizes of 3-30 m, at 1 m intervals, were created using the nearest neighbor resampling method. In total, 29 DEMs with different grid sizes were obtained. Four different scenarios of the channel initiation threshold were used to extract the drainage channel and let the slope length cutoff. Chinese soil loss equation was used to predict the soil loss. The results show that DEM grid size had different effects on the topographic factor. The average calculated slope steepness factor decreased with the increase of the DEM grid size in a linear decay function. The average slope length factor increased with DEM grid size when the drainage channel was not considered. It slightly decreased with DEM grid size and then increased when the drainage channel suitable for DEM grid size was used. However, comparing different grid sizes, the LS factor and the soil loss prediction of DEM grid size less than or equal to 10 m were close to those of 2 m DEM. The channel initiation threshold had effects on the extraction of slope length and then slope length factor. We found that the effect of DEM grid size on predicting soil loss depends on selection of suitable channel initiation threshold. [ABSTRACT FROM AUTHOR]

Enrichment ratio (ER) is widely used in nonpoint source pollution models to estimate the nutrient loss associated with soil erosion. The objective of this study was to determine the ER of total nitrogen (ER) in the sediments eroded from the typical soils with varying soil textures in Beijing mountain area. Each of the four soils was packed into a 40 by 30 by 15 cm soil pan and received 40-min simulated rainfalls at the intensity of 90 mm h on five slopes. ER for most sediments were above unity, indicating the common occurrence of nitrogen enrichment accompanied with soil erosion in Beijing mountain area. Soil texture was not the only factor that influenced N enrichment in this experiment since the ER for the two fine-textured soils were not always lower. Soil properties such as soil structure might exert a more important influence in some circumstances. The selective erosion of clay particles was the main reason for N enrichment, as implied by the significant positive correlation between the ER of total nitrogen and clay fraction in eroded sediments. Significant regression equations between ER and sediment yield were obtained for two pairs of soils, which were artificially categorized by soil texture. The one for fine-textured soils had greater intercept and more negative slope. Thus, the initially higher ER would be lower than that for the other two soils with coarser texture once the sediment yield exceeded 629 kg ha. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a dataset of the soil hydraulic parameters associated with two empirical soil functions (i.e., a water retention curve and hydraulic conductivity) using multiple pedotransfer functions (PTFs). The dataset is designed specifically for regional land surface modeling for China. The authors selected 5 PTFs to derive the parameters in the Clapp and Hornberger functions and the van Genuchten and Mualem functions and 10 PTFs for soil water contents at capillary pressures of 33 and 1500 kPa. The inputs into the PTFs include soil particle size distribution, bulk density, and soil organic matter. The dataset provides 12 estimated parameters and their associated statistical values. The dataset is available at a 30 × 30 arc second geographical spatial resolution and with seven vertical layers to the depth of 1.38 m. The dataset has several distinct advantages even though the accuracy is unknown for lack of in situ and regional measurements. First, this dataset utilizes the best available soil characteristics dataset for China. The Chinese soil characteristics dataset was derived by using the 1:1 000 000 Soil Map of China and 8595 representative soil profiles. Second, this dataset represents the first attempt to estimate soil hydraulic parameters using PTFs directly for continental China at a high spatial resolution. Therefore, this dataset should capture spatial heterogeneity better than existing estimates based on lookup tables according to soil texture classes. Third, the authors derived soil hydraulic parameters using multiple PTFs to allow flexibility for data users to use the soil hydraulic parameters most preferable to or suitable for their applications. [ABSTRACT FROM AUTHOR]

• There is a representative elementary area (REA) of biocrusts at the slope scale. • The REAs on the north-facing slope are larger than those on the south-facing slope. • The size of the REA is related to patch density of biocrusts. • This study provides a method for determining the REA of biocrusts. Biological soil crusts (biocrusts) are mixed communities of cyanobacteria, lichens and mosses in different ratios, contributing to important ecological functions in arid and semiarid regions worldwide. Biocrusts are spatially variable, and the variability in biocrust composition and coverage is scale-dependent. The following question can then be asked: What is the appropriate spatial scale for observing ecological functions? Without clarifying this issue, we cannot fully understand the ecological functions of biocrusts. The key to answering this question is to determine a threshold area, or representative elementary area (REA). Accordingly, we analyzed red–green–blue (RGB) images of 90 biocrust plots (2.0 m × 2.0 m) from nine revegetated grasslands in the Hilly Loess Plateau region of China. The variability in biocrust composition and coverage across the plot sizes was studied by gradually expanding the plot size from 0.01 m2 to 4.00 m2. The results showed that as the plot sizes increased from 0.01 m2 to 4.00 m2, the number of biocrust types logarithmically increased. Biocrust patches of a particular type (such as moss, cyanobacteria or lichen) were often characteristic of a plot size of 0.01 m2, whereas plot sizes larger than 0.25 m2 supported mixed biocrusts of multiple patch types. The variability in coverage of mixed biocrusts logarithmically decreased with increasing plot sizes. The coverage of mixed biocrusts maintained an approximately constant value after a certain critical plot size was reached (1.00 m2 in this study). Our data indicated that REAs of mixed biocrusts exist at the slope scale. The REAs of mixed biocrusts were 0.5–1.0 m2, 1.5–2.5 m2 and 3.0–3.8 m2, with alpha (α) values of 0.1, 0.05 and 0.01, respectively. The size of the REAs on the north-facing slope was larger than that on the south-facing slope, and the patch density of biocrusts had an important influence on the REAs. The results of this study could provide a method for determining the REAs of mixed biocrusts and guide surveys and experimental layouts. [ABSTRACT FROM AUTHOR]

Abstract: The Stochastic generation of storm patterns is often necessary for driving process-based hydrological and ecological models. CLIGEN is the only weather generator being able to generate internal storm patterns. Its goodness needs to be evaluated for its proper application. This paper aims to find the advantages and limitations of CLIGEN on semiarid areas and provide references for custom-built weather generators for the Loess Plateau. The daily rainfall time series (1957–2002) and breakpoint rainfall data (more than 20 years) on six stations on the Loess Plateau were used to estimate input parameters for CLIGEN and to compare with CLIGEN-generated 50 years of storm data. Precipitation occurrence (wet day and dry day sequence) is well-simulated without significant difference across months and sites. Errors of monthly average number of wet days range from −0.67 to 1.08 days, standard deviations range from −1.19 to 0.76 days, and the distributions of continuous number of wet and dry days on the semiarid Loess Plateau are adequately simulated. Daily rainfall amount is not simulated as well as precipitation occurrence. The relative errors of average daily rainfall range from −12.93% to 8.64% and those of standard deviations range from −21.35% to 27.46%. During the rain seasons (May–September), among 30 month–location combinations, all the Mann–Whitney tests for the means passed, 47% for squared ranks tests rejected the null hypothesis of equality of standard deviations, and 73% for K–S test suggested that the generated and measured distributions of daily rainfall were different at 0.01 level of significance Three variables to describe internal storm patterns in CLIGEN are storm duration, relative peak intensity, and time to peak. Storm duration was not well-reproduced because none of squared ranks tests and K–S test passed at the significance level of 0.01. The frequency of short duration storms (<300 min) was over-predicted while frequency of long duration storms (400–1200 min) was significantly under-predicted. The distribution of maximum 5 min rainfall intensity (ip5) was well-simulated for four sites out of the six because all tests passed. However, generated maximum ip5 for all six sites are around 190 mm/h, which are much larger than the measured (70 to 150 mm/h). Ip30 is simulated better than ip5, suggesting that CLIGEN can reliably generate rainfall erosivity. Time to peak was well-simulated because all the tests passed with P values significantly greater than the significance level of P =0.01. Improvement for CLIGEN has to be made in terms of the daily rainfall simulation in rainfall-concentrated seasons and storm pattern generation in order to generate reliable rainfall time series on the Loess plateau. [Copyright &y& Elsevier]

Soil and water conservation (SWC) measures can be adopted to conserve soil and water and improve soil fertility. The degree to which SWC measures improve soil fertility is affected by the type of SWC measure, soil type, climate, etc. The purpose of this study was to study the effect of the main SWC measures implemented in the Beijing mountain area on soil fertility. Six runoff plots, including a fish pit (fallow) (FPF), fish pit (Platycladus orientalis L. Franco) (FPP), narrow terrace (fallow) (NTF), narrow terrace (Juglans regia L.) (NTJ), tree pan (Juglans regia L.) (TPJ), and fallow land (FL), were established to analyze the differences in soil fertility in the Beijing mountain area. Soil samples were collected in 2005 and 2015 from the six runoff plots. Soil particle size; soil total nitrogen (TN), total phosphorous (TP), total potassium (TK), alkali-hydrolysable nitrogen (Ah-N), available P (Av-P), and available K (Av-K); and soil organic matter (SOM) were measured. The soil integrated fertility index (IFI) was calculated. The results showed that the soil nutrient content and IFI significantly decreased from 2005 to 2015 in the FL plot and significantly increased in the five runoff plots with SWC measures. Compared to the other runoff plots with SWC measures, the FPP plot more significantly improved the soil nutrient content and IFI. The TN, Ah-N, Av-K, SOM, and IFI in the FPP plots increased by 98%, 113%, 61%, 69 and 47%, respectively, from 2005 to 2015. The IFI for the FPP, NTJ, and TPJ exceeded the average IFI of the farmland soil in the study region. The results indicated that the combination of engineering practices and vegetative measures effectively improved soil fertility. These results may be helpful for selecting SWC measures, land-use planning and monitoring and assessing soil fertility. [ABSTRACT FROM AUTHOR]

Soil erosion has been a major environmental issue in China. However, the overall rate and the variability in runoff and soil loss of different regions and land uses in China have not been reported in the literature. In this study, an extensive database of runoff plots in China was compiled. Runoff and soil loss rates of sheet and rill erosion under natural conditions based on plot studies, are reviewed. The history of plot studies in China is briefly introduced, and basic information, such as the geographic distribution of soil erosion monitoring sites, the distribution of slope length and the slope gradient of runoff plots, is described. The runoff and soil loss rates of five water erosion regions in China were analyzed in terms of the main land use types. The soil loss rate was 30.87–107.44 t ha − 1 a − 1 on fallow land and 7.65–49.38 t ha − 1 a − 1 on farmland under conventional tillage. The land use types with permanent cover experienced the lowest soil loss rates, which were 0–1.89, 0.28–8.06 and 3.98–1.57 t ha − 1 a − 1 for forest, shrub and grassland, respectively. In China, the regional differences in the soil loss rate were mainly observed on fallow land and farmland, whereas almost no differences were observed on forest, shrub and grasslands. The soil loss rates of forest, shrub and grasslands showed no significant differences worldwide. However, the soil loss rates of farmland with conventional tillage in northwest and southwest China were much higher than in most other countries. This indicated that farmlands in China are still suffering from a very serious erosion problem that requires additional future attention. This study provided a broad assessment of sheet and rill erosion for prioritizing problems and selecting the appropriate erosion control practices. [ABSTRACT FROM AUTHOR]

Abstract: We developed a multi-layer soil particle-size distribution dataset (sand, silt and clay content), based on USDA (United States Department of Agriculture) standard for regional land and climate modelling in China. The 1:1,000,000 scale soil map of China and 8595 soil profiles from the Second National Soil Survey served as the starting point for this work. We reclassified the inconsistent soil profiles into the proper soil type of the map as much as possible because the soil classification names of the map units and profiles were not quite the same. The sand, silt and clay maps were derived using the polygon linkage method, which linked soil profiles and map polygons considering the distance between them, the sample sizes of the profiles, and soil classification information. For comparison, a soil type linkage was also generated by linking the map units and soil profiles with the same soil type. The quality of the derived soil fractions was reliable. Overall, the map polygon linkage offered better results than the soil type linkage or the Harmonized World Soil Database. The dataset, with a 1-km resolution, can be applied to land and climate modelling at a regional scale. [Copyright &y& Elsevier]

Abstract: Soil loss has become one severe problem in black soil areas of Northeast China after several decades of cultivation. Gully erosion is one of its main components. In this study, short-term gully retreat was monitored from 5 active gullies selected in representative black soil area during April 2002 to June 2004, using differential global positioning system (GPS). With the support of geographic information system (GIS), multitemporal digital elevation models (DEM) were constructed from the data collected by GPS and then used for further analysis. This presents a new method to compute the retreat rate of gully heads and the rate of soil losses caused by gully erosion. The results indicate that the average volumetric retreat rate was 729.1 m3 year−1, corresponding with an average linear retreat rate of 6.2 m year−1 in gully head and planimetric changes of 323.6 m2 year−1 during the two monitored years, but more erosion took place during the second and third monitored period compared to the first. The erosion by freeze thawing and snowmelt accounts for a large percent. And this will be emphasized when rainfall is added in spring. If only considering the third monitored period, the conservatively estimated retreat rate by freeze thawing and snowmelt (i.e. before rainy season) may even reach 8.6 m year−1 in gully head, with a volumetric rate of 120.9 m3 year−1 and planimetric changes of 173.6 m2 year−1. These results reveal that gully erosion is a great threat in the study area and conservation measures are urgently needed. Based on the analysis of multi-temporal DEM, one conceptual model for gully developing in black soil of Northeast China is proposed, which is supported by the data. [Copyright &y& Elsevier]

A dam and weir system was constructed to measure the discharge of water and sediment from a selected small catchment on the Loess plateau in China. The aim of the system described here was to collect data on discharge and sediment content during occasional summer storms. These data can be used for calibrating and validating the LISEM erosion model. A V-notch weir was selected since it can measure a wide range of discharges. The measurement structure was equipped with an ultrasonic sensor to measure the water level. The system automatically switched on as soon as rain had been detected and the water level data were stored when a certain level threshold was surpassed. As a back-up system a flow meter was used, while a local farmer had also been hired to manually record water level during events. Sediment content of the runoff was determined on samples taken by an automatic sampler and a local farmer took additional samples. The system operated from April 1998 until September 2000. In this period, six events occurred and data could be collected during five of those. The data were corrected to make them useful for comparison with erosion simulation results. The collected data show that runoff only occurs during high-intensity rainstorms that produce more than about 11 mm of rain. [Copyright &y& Elsevier]

An automatic monitoring system was constructed to intensively study the water–profile–runoff interactions during rain events, of a hillslope gully. The system was installed on the Loess plateau in the Shaanxi province in northern China. The primary goal was to obtain a better understanding of soil erosion processes in this district to aid in better management. To accomplish this, infiltration and runoff data for running, calibrating and validating the LISEM erosion model was needed. The system presented here consisted of 29 Time Domain Reflectometry (TDR) water content sensors that monitored the water content variation in time. Sensors were installed in different subsystems throughout the gully geometry such as in the cropland surrounding the gully, in some gully slopes and in the gully floor. At the outflow point of the gully, an H-flume was installed in order to measure the actual discharge of the gully system and to measure directly the sediment concentration in the discharge. The monitoring system was programmed in this way so that more measurements were recorded when a rainstorm occurred. Installation took place in April 1998 and it was used until September 2000. In 1998, five major rain events were recorded, which generated runoff and erosion, in 1999 and 2000 only one. Cropland measurements showed high water contents and high infiltration rates all through the measuring period and also showed a strong reaction to precipitation. The sidewalls of the gully showed much lower water contents where only very shallow parts showed some infiltration during rain showers, while steep parts of the gully, such as pipes and vertical walls, showed an extremely low water content and practically no water content variation with time. Simulation results confirmed the suspicion that these areas are an important source for Hortanian overland flow within the gully system. Model simulations further showed that most of the sediment being eroded from the gully system was coming from rills and smaller gullies being cut into the main gully bottom. Saturation excess overland flow proved to be dependent on the characteristic of the rain event as well as on the water content of the soil at the beginning of the event. [Copyright &y& Elsevier]

Slope length and slope steepness are the two topographic factors (L and S) used in the Universal Soil Loss Equation (USLE) for soil erosion prediction. These factors are usually extracted from the digital elevation models (DEM). We hypothesized that different DEM resolutions and sources influence extracted topographic factors and therefore soil loss estimation. The objective of this study was to quantify the effect of different DEM resolutions on the topographic factor calculation and consequently soil loss prediction on different geomorphological types in China and United States. We selected three typical landforms of plains, hills and mountains in both countries. We used 1) open source DEMs of 3-, 10-, 30-, and 90-m in the United States, and 2) DEMs generated with 1:10,000 and 1:50,000 topographic maps in China to extract topographic factors using a LS software tool. The Chinese Soil Loss Equation (CSLE) was used to calculate average annual soil loss. The results showed that different DEM resolutions had different effects on the extracted L and S factors. Slope length and the L factor were overestimated as DEM resolutions coarsened, and the trend of the overestimation in different landforms was the same. Slope steepness and the S factor were underestimated as DEM resolution decreased in all landforms. However, the LS factor as a product of L and S factors, which reflects relative soil loss if the other factors are held constant, are less sensitive to DEM resolutions than either L or S factor alone due to partial error cancelation. Thus, the LS factor is not as greatly affected by DEM resolutions as either L or S factor alone. The relative soil loss errors are similar for all DEMs, and "good results for wrong reasons" are obtained with coarser DEMs. Overall results indicate that except for the 90 m DEM for certain occasion, all DEMs may be used to estimate soil loss for all types of terrains for practical application, as far as the relative soil loss errors are concerned. However, in the range of 3–90 m resolutions, for the sake of good practice and solid scientific support, higher resolution DEMs if available ought to be used to minimize estimation errors of L and S factors and consequently to increase confidence of soil loss prediction. • A topographic LS software and the Chinse Soil Loss Equation were evaluated. • Slope length and its L factor were overestimated as DEM resolutions coarsened. • Slope steepness and its S factor were underestimated as DEM resolutions decreased. • The LS factor is not as greatly affected by DEM resolutions as either L or S alone. • All DEMs may be used to estimate soil loss for practical and economical concerns [ABSTRACT FROM AUTHOR]

• K s was investigated during the maize growing season on a typical black soil slope. • Root growth, precipitation, management practices caused strong temporal K s variability. • Temporal K s variation was dominated by BD, followed by SAND, SOC, P and WAS, successively. Saturated hydraulic conductivity (K s) is highly variable in both space and time. Compared to its spatial variability, however, the temporal K s variability has rarely been studied or taken into account in the hydrological modelling. The objectives were to characterize the slope-scale temporal variability of K s and to diagnose the primary factors regulating K s variation during the growing season. In the black soil region of northeast China, a typical slope farmland dominated by silt loam was selected and divided into five sections with respect to soil erosion. Soil samples were collected in each section at approximately every 3 weeks during the maize growing season, and K s, bulk density (BD), land surface roughness, wet-aggregate stability (WAS), soil organic carbon content (SOC), clay and sand contents (SAND) were investigated. Mainly owing to root growth, precipitation and agricultural management, strong temporal variability of K s was observed in each of the five sections, as the corresponding coefficients of variation all exceeded 35 %. Using the redundancy analysis (RDA) and classical correlation analyses, the primary variables controlling K s distribution varied among sections, i.e., precipitation (P) and SAND in the erosive section and BD in the others. The predominance of BD was also manifested when performing RDA and structural equation modelling (SEM) over the entire slope covering all five sections. The other significant factors included SAND, SOC, P and WAS, in the decreasing order of direct path coefficient. In addition, these factors also indirectly affected K s through their influence on BD and/or other factors. These findings demonstrate the strong temporal variability of K s throughout the maize growing season and intricate interactions of K s with related factors, and have important implications for hydrological modelling and agricultural production in the black soil region of northeast China and other similar regions. [ABSTRACT FROM AUTHOR]

• Main unpaved roads experienced more severe erosion than secondary roads and trails. • Gully erosion was over 100 times as much as rill erosion on main unpaved roads. • Contributing area and road segment gradient could better predict road erosion. • Changing cropland to woodland/shrubland could decrease road erosion. Soil erosion causes agricultural land degradation. As one of the indispensable components of the agricultural system, unpaved roads are significant sediment sources, but road erosion is often overlooked because of the relatively small areas that roads cover. This study aims to investigate the severity of road erosion under extreme rainfall and ascertain the dominating factor. We investigated road erosion in two small watersheds after a heavy rainstorm to measure rill and gully erosion on three types of road in the field and determine the factors affecting that erosion with remote sensing images and geographic information system (GIS). Using Google images before the storm and unmanned aerial vehicle (UAV) images after the storm, we interpreted land use and measured geomorphological and vegetation factors. In 579 road cross-sections within 63 road erosion segments found along the 10.42 km roads surveyed, the average soil loss was 804.77 t ha^-1 from main unpaved roads, 471.78 t ha^-1 from secondary unpaved roads, and 147.46 t ha^-1 from trails. Gully erosion predominated over rill erosion on all three types of road. The average rill erosion was 0.41, 0.17, and 0.02 cm, compared with 4.88, 3.15, and 1.05 cm of gully erosion on the main unpaved roads, secondary unpaved roads, and trails, respectively. The contributing area dominated over other factors associated with road erosion under heavy rainfall and could explain 84.9% of the erosion from the road segment to which it drains based on the linear regression analysis. Furthermore, a nonlinear regression model with the contributing area and road segment gradient as predictors precisely predicted road erosion (coefficient of determination, 0.970). [ABSTRACT FROM AUTHOR]

Compound erosion of wind and water is a serious global environmental problem, and the relative magnitude of water versus wind erosion has important implications for future studies and soil conservation practices. However, currently, field measurements of compound erosion are rarely reported, probably due to the lack of generally accepted wind erosion measurement methods. In this study, an agricultural field at the northern end of the Loess Plateau was selected to measure the compound erosion from 2012 to 2014, in which water erosion was measured by runoff plots, while wind erosion was measured using BSNE samplers. The results indicated that: 1) annual water erosion ranged from 8.1 to 89.4 t ha−1 a−1 with a mean of 43.8 t ha−1 a−1, while wind erosion ranged from 0.82 to 2.12 t ha−1 a−1 with a mean of 1.58 t ha−1 a−1; 2) water erosion primarily occurred in the summer, while wind erosion occurred in the spring, and substantial variability was revealed on both the interannual and intra-annual scales for both erosion processes; 3) the compound erosion was temporally alternated and spatially overlaid in the selected field, and wind erosion only accounted for 3% of the compound erosion. Although water erosion greatly exceeded wind erosion for the selected agricultural field, the need for measuring and monitoring over a longer period to cover the natural variability of weather conditions is highlighted. The relative magnitude of water versus wind erosion was quantified, but more relevant studies are needed, since these studies usually have important implications for future studies and soil conservation practices. • A new method for measuring field wind erosion was proposed. • The relative significance of wind versus water erosion was measured. • Water erosion only accounted 3% of the total erosion in the Loess Plateau. • The measured rates in this study were compared with relevant studies. [ABSTRACT FROM AUTHOR]

• SWCMs reduced the flood magnitudes and sensitivities to rainstorm events. • Control effects of SWCMs on flood decrease with rainstorm intensity. • Small watersheds are more likely to cause large flood peaks in Loess Plateau. • Bare soil of agricultural terraces must be protected in earth-rocky mountainous areas. Flash floods resulting from extreme rainstorms seriously threaten regional socioeconomic development. However, few studies have explored the general impacts of soil and water conservation measures (SWCMs) on flood peaks during extreme rainstorms through multiple field investigations. On the basis of field surveys of three rainstorm events in Shaanxi, Shandong, and Henan provinces, the effects of vegetation and agricultural terraces on flood peaks were investigated in 75 small watersheds in northern China. Compared with watersheds dominated by sloping cropland, the flood peak modulus of watersheds dominated by forest land, grass land, and agricultural terraces decreased by 54.75%, 47.80%, and 53.65%, respectively; the peak shaving effects (PSEs) of SWCMs were stronger during minor floods. Soil and water conservation measures reduced the flood magnitudes of small watersheds and their sensitivities to rainstorm events; the PSEs were positively correlated with the area of SWCMs. In earth-rocky mountainous areas, the PSEs of forest land were stronger than those of grassland and agricultural terraces, while in the loess hilly-gully areas, the PSEs of agricultural terraces were stronger than those of other SWCMs. In loess hilly-gully areas, the flash floods demonstrated a phenomenon of small rainfall amounts but substantial flood peaks. Besides the reasonable installation of SWCMs on slopes, appropriate channel measures (e.g., check dams) are warranted to cope with extreme rainstorm events. In northern earth-rocky mountainous areas, intercropping management should be promoted to cover bare soil on orchard agricultural terraces. Our results provide a theoretical basis for combating extreme rainstorm disasters. [ABSTRACT FROM AUTHOR]

• Water-carbon-related ecosystem services were investigated in the Loess Plateau. • Water yield and net primary productivity were improving in the last 20 years. • Increased precipitation offset afforestation-induced carbon–water trade-off. The Loess Plateau of China is one of the regions with the most serious soil erosion globally. The ambitious "Grain for Green" project was there implemented to restore degraded ecosystems, profoundly changing the water yield and carbon sequestration ecosystem services. To understand the changes of water- and carbon-related ecosystem services (hereafter WCES) in the Loess Plateau, this study combined the CASA (Carnegie-Ames-Stanford Approach) model and InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model to thoroughly reveal the changes and intrinsic linkages of water yield and net primary productivity since the "Grain for Green" project in the Loess Plateau. The results show that the WCES of the Loess Plateau were increasing since 2001, dominated by both the climate change and human afforestation. The water yield and net primary productivity showed strong synergistic effects in 80% of the Loess Plateau, mainly resulting from the rapid increase of precipitation in recent years. The increasing atmospheric precipitation contributed to more WCES provisions, which may have offset the trade-off between WCES caused by large-scale afforestation. In view of the synergistic effects of WCES, enhancing water input into the ecosystem may be an effective measure to respond with future WCES degradation in dry years, such as artificial basin-cross water transfer project. Despite the low correlation between teleconnection factors and WCES, the low water yield and reduction of net primary productivity may be associated with a strong El Niño event in 2015. This study assists in a wise decision-making on the future "Grain for Green" and ecological management in the Loess Plateau. [ABSTRACT FROM AUTHOR]

• Beiluo River basin saw considerable land use change over the past 50 years; 9-fold increase in upper reach forests. • Satisfactory applicability of Chinese soil loss equation on Loess Plateau verified by sediment load datas. • The soil loss rate in the Beiluo River basin has decreased from 4090 to 890 t·km−2·yr−1 over the last 50 years. • Vegetation restoration was the dominant factor in soil loss reduction, with a contribution of more than 78 %. The Chinese Loess Plateau has experienced large-scale land use changes in the past few decades. Understanding how land use change affects soil erosion is critical in the region's ecological construction and land management. In this study, the Beiluo River Basin in the core area of the Loess Plateau was selected to investigate the effects of land use changes on soil loss rates over the last 50 years. Results show that the land use has changed considerably, mainly reflected in the upper reaches. From 1970 to 2020, cropland in the upper reaches decreased by 54 %, directly leading to a 9.1-fold increase in forested land. Landsat-NDVI shows vegetation coverage increased from 21.1 % to 69.9 % over time. The Chinese Soil Loss Equation (CSLE) was used and confirmed to be satisfactory with a high coefficient of determination (R2, 0.89) and a strong Nash–Sutcliffe efficiency coefficient (0.72), although an underestimation exists. The specific soil loss simulated in the upper reaches maintained a high rate of around 8,000 t·km−2·yr−1 from the 1970s to the 1990s, dramatically dropping to 3,058 t·km−2·yr−1 in the 2000s, then attenuated to 1,321 t·km−2·yr−1 in the 2020s. For the entire basin, soil loss rates dropped from 4,090 to 1,848 and 890 t·km−2·yr−1 from the 1970s to the 2000s and 2020s, respectively. Attribution analysis showed that the dominant factor of the change in soil loss rates in the 1980s and 1990s relative to the 1970s was the change in rainfall erosivity for the entire watershed. However, vegetation restoration rapidly converted to the dominant factor contributing 78.3 % to soil loss decrease in the 2000s. The shift is evident in each reach of the basin except the terrain-plain area with the majority of farmland. The findings are helpful for sustainable land use planning and socio-economic development on the Loess Plateau and in similar areas. [ABSTRACT FROM AUTHOR]

As the head source of the two longest rivers in China and the longest river in Southeast Asia, the East Qinghai-Tibetan Plateau (QTP) is experiencing increasing thaw snowmelt and more heavy precipitation events under global warming, which might lead to soil erosion risk. To understand the potential driving force of soil erosion and its relationship with precipitation in the context of climate change, this study analyzed long-term variations in annual rainfall-runoff erosivity, a climatic index of soil erosion, by using the Mann-Kendall statistical test and Theil and Sen's approach in the Source Region of the Three Rivers during 1961–2012. The results showed the followings: (i) increasing annual rainfall-runoff erosivity was observed over the past 52 years, with a mean relative trend index ( RT 1 ) value of 12.1%. The increasing trend was more obvious for the latest two decades: RT 1 was nearly three times larger than that over the entire period; (ii) more precipitation events and a higher precipitation amount were the major forces for the increasing rainfall-runoff erosivity; (iii) similar rising trends in sediment yields, which corresponded to rainfall-runoff erosivity under slightly increasing vegetation coverage in the study area, implied a large contribution of rainfall-runoff erosivity to the increasing sediment yields; and (iv) high warming rates increased the risk of soil destruction, soil erosion and sediment yields. Conservation measures, such as enclosing grassland, returning grazing land to grassland and rotation grazing since the 1980s, have maintained vegetation coverage and should be continued and strengthened. [ABSTRACT FROM AUTHOR]

The effects of rainfall intensity on erosion processes for intra-storm variations are extensively investigated based on rainfall simulation experiments. However, there is a distinction between natural and simulated rainfall. Soil loss data from a total of 84 erosive storms from 2006 through 2013 with hyetograph rainfall data were collected from five plots located in Beijing, each with soils from different Chinese zones, to investigate the effects of erosive storm patterns on soil loss under natural rainfall conditions and to detect if this influence was consistent among the five soil types. The storms were divided into four patterns according to the period of the most concentrated rainfall, including advanced, intermediate, delayed, and uniform patterns. The results indicate that 1) the prevalent storm pattern in Beijing is advanced, which accounts for 43% of storms and contributes the most to total soil loss (approximately 55 to 68%). 2) Storm pattern significantly affected soil loss, with the delayed pattern yielding more soil loss than the other three patterns after taking into account EI 30 . 3) The effect of storm patterns on soil loss was consistent between the five soil types. 4) Coefficients for quantifying the effects of storm pattern on soil loss were not significantly different among these five soils, but exhibited significant differences among the storm patterns, e.g., the coefficient for the delayed pattern was 2.07, for the uniform pattern was 0.42, and for the advanced and the intermediate patterns were approximately 1. Rainfall erosivity generated by an erosive storm with a known pattern could be estimated by multiplying the corresponding adjustment coefficient, which would further improve the accuracy of soil erosion prediction, especially for storm level prediction. [ABSTRACT FROM AUTHOR]

Saturated hydraulic conductivity (K s) is controlled by a suite of soil processes operating at various scales. Little is known about the spatial variability of Ks along a slope and how it is changed through the planting operation process and the specific scales at which the controlling factors function. The objective was to characterize the scale-dependent relationships between K s and various soil processes and thereby to identify the primary controlling factors of K s. On a typical slope transect of 900 m in the black soil region of Northeast China, K s and six soil properties of bulk density (BD), wet-aggregate stability (WAS), surface roughness (SR), soil organic carbon content, sand and clay contents were investigated in an interval of 20 m before and after mechanical sowing in the spring. Statistical correlation analysis, its combination with noise-assisted multivariate empirical mode decomposition (NA-MEMD) and wavelet coherence were employed to examine the interactions between K s and each factor at different spatial scales. The BD was admittedly the dominant factor controlling K s, followed by WAS and SR before and after sowing, respectively. The statistical correlation analysis only detected the significant interactions between K s and BD, whereas the essential influence of WAS and SR were revealed upon frequency component decompositions by NA-MEMD and biwavelet coherency. Applying multiple wavelet coherence, BD was believed adequate in explaining K s variability before sowing, whereas the combination of BD and SR was suggested in the case after sowing. These findings hold important implications for precise K s estimations in the black soil region of Northeast China as well as other similar regions, and also demonstrate the effectiveness of NA-MEMD and wavelet coherence in untangling complex scale-dependent relationships among soil processes. ● K s and six factors were measured before and after sowing along a slope in NE China. ● Scale-dependent relationships were observed between K s and each soil factor. ● BD was admittedly the primary factor, followed by WAS before and SR after sowing. ● Multiple wavelet coherence believed BD was adequate for K s estimation before sowing. ● The combination of BD and SR was selected to explain K s variability after sowing. [ABSTRACT FROM AUTHOR]

Abstract: Gully erosion is an important environmental hazard in the black soil region of northeastern China. It is a primary sediment source in the region which needs appropriate soil conservation practices. Gully incision in rolling hills typical of this region was monitored using real-time kinematic GPS to assess the rates of gully development and the resultant sediment production. From 2002 to 2005, gully heads in the study area retreated between 15.4 and 33.5 m, giving an average retreat rate of 8.4 m yr−1. Field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr−1, which is equivalent to 326 to 2355 t yr−1, with gully-head retreat accounting for 0 to 21.7% (4.4% in average). The sediment delivery ratio was especially high during the summer rainy season (56% in average). Sediment production by ephemeral gullies and permanent gullies was 1.5 times greater than that from surface erosion. Gully heads retreated faster in the spring freeze–thaw period than in the summer. The stage of gully development could be identified based on short-term changes in the gully erosion rate. [Copyright &y& Elsevier]

In soil erosion models digital elevation models (DEMs) play an important role. Most interpolations from contour lines fail to address multi-value cells (MVCs) problems and therefore find it difficult to deal with steep slopes. These interpolation methods randomly assign a single value for MVCs and use this value in interpolation for nearby cells. This approach is very inaccurate. The frequency of MVCs and the problem caused by them was investigated, and the errors created by using the random values for MVCs was analyzed in this paper. A special treatment for MVCs and practical solution to create more accurate interpolation cell values in DEM building was developed. The new approach involves storing additional information of contour lines that go through the MVCs, such as maximum height and minimum height values, and the cardinal orientation relationship of the contour lines. A special MVC filter kernel was developed to decide the appropriate elevation value for interpolation. The computation method is based on raster data. An area on the Loess Plateau in North China was selected as an example to demonstrate the problems of the previously common used approach and to show results of the new method. [Copyright &y& Elsevier]

Structure from motion (SfM) photogrammetry is a cost-effective topographic survey tool capable of producing high-quality 3-dimensional structure of a landform. Yet its application has rarely been reported in rill and interrill erosion at the relatively small spatial scales, especially when taking place in the loess that is vulnerable to erosion. The objective was to examine the accuracy and limits of SfM in quantifying rill and interrill erosion occurring in a typical loess during consecutive rainfall simulations. The loess collected from the plough layer of a cropland in the Loess Plateau of China was packed into a 200 × 100 × 35 cm runoff plot and received simulated rainfall at the intensity of 90 mm h−1 on three slopes of 10°, 15° and 20°. A portable laser scanner (LS) and SfM were used to measure soil surface at every 30 min until rill emergence and after another 30-min rainfall aiming to study rill development. Meanwhile, runoff and sediment samples were collected at the plot outlet and oven-dried to calculate the soil loss. The results showed that the elevation differences calculated by subtracting digital elevation models (DEMs) derived by SfM and LS mainly fell between −2 and 2 mm. Moreover, the root mean square error (RMSE) and mean absolute error (MAE) were mostly smaller than 3 mm, suggesting accurate soil erosion measurement made by SfM at the plot scale. Considering the surface variations, the relative RMSE and MAE, i.e., dividing over the mean elevations measured by LS, were found to decrease as soil erosion proceeded and rills emerged. The rill morphology comparison, however, suggested a better fit of SfM for rills larger than 9 cm in maximum surface width, 6.0 × 10−2 m2 in area and 0.9 × 10−3 m3 in volume. In accordance with DEM comparisons, the soil losses estimated by SfM and LS were statistically similar. Nevertheless, these values were much greater than the amount of sediments collected for the early simulation runs, which might be explained primarily by the settling of loess when subject to heavy rainfall. But as rainfall continued and rills further developed, the misestimations made by LS and SfM remarkably dropped, i.e., from −17.8% to 4.9% and from −18.1% to 4.3%, respectively. These findings suggest a generally higher accuracy of SfM in quantifying rill erosion with more fluctuating soil surface than in interrill erosion measurement. • SfM was evaluated for rill and interrill erosion measurements using rainfall simulations. • DEMs and soil losses derived by SfM and LS were rather similar. • SfM was applicable for morphological descriptions of relatively larger rills. • SfM had a generally higher accuracy in quantifying rill erosion with more fluctuating surface. [ABSTRACT FROM AUTHOR]

The upper reaches of the Hanjiang River Basin (HM-CSNWTP) is the headwater source for the middle route of China's South-to-North Water Transfer Project (M-CSNWTP), as well as the north-south transitional zone of central China, and is characterized by high precipitation sensitivity and variability. Changes in precipitation patterns can affect the potential runoff generation capacity of the HM-CSNWTP. Therefore, this study was focused on exploring the dynamic precipitation patterns over the HM-CSNWTP and the potential runoff generation capacity of this region at annual and seasonal timescales. Daily precipitation data from 34 meteorological stations for the period 1961–2016 were collected in order to estimate 4 categories of rainfall indices: average daily precipitation on all days (ADP) and on rainy days (ARP), total amount (TP), and rainy days (TD). The non-parametric Mann-Kendall test, LOWESS smoothing, and collaborative kriging method were implemented. The statistical results indicated that: (1) The annual ADP over the basin decreased slightly, at the rate of −0.22%/10a (−0.002 mm/d/a). Seasonally, summer ADP increased by 1.4%/10a (0.005 mm/d/a), while decreasing ADP values were detected in other seasons. Large increases in annual and summer ARP were found, at rates of 3.73%/10a (0.018 mm/d/a) and 3.72%/10a (0.039 mm/d/a), over the HM-CSNWTP, mainly in the southwestern area (Region III), due to the large changes of annual and summer ARP. Annual and summer ARP increased at significant rates of 7.22%/10a (0.034 mm/d/a) and 10.64%/10a (0.083 mm/d/a), respectively. (2) Decreasing light rainfall amounts (TP 0-10) and days (TD 0-10), and increasing heavy rainfall amounts (TP >25) and days (TD >25) were detected over the HM-CSNWTP, especially for Region III, in which TP >25 and TD >25 increased by 7.00%/10a (1.076 mm/a) and 5.37%/10a (0.023 d/a), respectively. (3) In the wettest assumption scenario, the estimated annual, spring, summer, autumn, and winter runoff depths were 912.9 mm, 183.0 mm, 410.6 mm, 259.0 mm, and 60.3 mm, respectively. In the driest assumption, the estimated annual, spring, summer, autumn, and winter runoff depths were 131.4 mm, 35.6 mm, 65.7 mm, 27.8 mm, and 2.3 mm, respectively, and the planned diversion water accounted for 76.1%, 63.2%, 70.0%, 102.2%, and 156.5% of the annual and seasonal driest assumption runoff depths, respectively. Thus, the water diversion of the M-CSNWTP in the driest assumption may trigger water shortages and environmental disasters in the lower reaches of the Hanjiang River Basin, especially at annual, autumn, and winter timescales. These findings provide some basic information for local water resource management in the HM-CSNWTP. • Average daily precipitation decreased by −0.22%/10a (−0.002 mm/d/a), while the precipitation intensity increased at the significant rate of 3.73%/10a (0.018 mm/d/a) over the basin from 1961–2016. • Decreasing light rainfall amounts and days, and increasing heavy rainfall amounts and days were detected over the HM-CSNWTP. • Annual potential runoff generation capacity over the HM-CSNWTP in the wettest and driest assumption years were 912.9 mm and 131.4 mm, respectively. [ABSTRACT FROM AUTHOR]

• Soil and nutrient redistribution caused localized land degradation. • The SOC and TN were halved on the sloped cropland compared to the nearby tree rows. • Atomic ratios of C:N:P differed as the slope curvatures diverted. • Minor geomorphic features govern localized biochemical cycling of major nutrients. • Topography-specific conservation practices must be integrated to local land use policy. Erosion-induced land degradation in the northeastern China, the Chinese breadbasket, has become one of the biggest risks to national food security. Apart from depleting topsoil, incising gullies, and waterlogging depositional sites, slope-scale erosion also spatially redistributes soil nutrients and introduces localized soil degradation. This requires to systematically understanding topography-specific spatial distribution patterns of eroded soil compositions and the relative abundance of each nutrient at different topographic settings. In this study, topsoil at predetermined space intervals were collected from two adjacent but differently curved segments (convex vs. concave) on a sloped cropland in northeastern China. The spatial distributions of topsoil soil organic carbon (SOC), total nitrogen (TN), total phosphorous (TP), and the variations of their atomic ratios were compared. Our results show that: (1) Compared with the nearby undisturbed tree rows, the SOC and TN was halved on the investigated slope, demonstrating great degradation since the land use conversion. (2) The spatial distribution of topsoil nutrients were evidently topography specific, with the SOC being comparable at slope summit, but declining from 27.57 to 4.72 g kg−1 (depletion ratio of 0.17) at the convex segment meanwhile accumulating up to 34.71 g kg−1 (enrichment ratio of 1.26) at the concave segment. Similar but more deviated spatial patterns were also observed on the TN and TP. (3) The atomic ratios of C:N:P also differed as the slope curvatures diverted, by being more variable from 51:3:1 to 105:6:1 along the convex segment but rather stable between 74:5:1 and 89:5:1 along the concave segment. (4) The lower content of SOC and the heavier δ 13C along the convex segment suggest more advanced mineralization of C and thus greater susceptibility of C-limitation. Meanwhile, the slightly lower C:N ratios and the greater δ 15N along the concave segment indicate greater stability of C, more advanced mineralization of N and thus likely a N-limited process. Overall, our findings demonstrate the controlling influences of minor geomorphic features to on-site soil dislocation and localized degradation at slope scale. Apart from general soil conservation measures, topography-specific practices must also be integrated to local land use policy to effectively target localized land degradation. [ABSTRACT FROM AUTHOR]

• Soil erosion significantly decreased soil structural stability and OC, N and P. • Most of the effects of erosion were enhanced with the intensity of erosion. • Effects of the conversion of forest to cropland on OC and N were greater than effects of light erosion. • Effects of the conversion of forest to cropland were smaller than effects of moderate and heavy erosion. • Deposition increased soil OC, N and P due to burial. Converting forest to cropland generally results in the deterioration of soil structure and the loss of soil organic carbon (OC) and nutrients, while agricultural soil erosion accelerates such degradation. To understand how soil structure, OC and nutrients respond to the conversion of forest to cropland and agricultural erosion, we compared soils between forest and cropland that was established in forest 60 years ago, and among croplands suffering various intensities of erosion (from non-erosion to heavy erosion). Soil samples were collected from 0−70 cm depth for the measurement of bulk density, OC, nitrogen (N) and phosphorous (P). The soil structural stability index was calculated. We showed that the conversion of forest to cropland decreased the soil structural stability and the concentrations and stocks of OC and N in the top 30 cm soils but had no effects on P. Soil erosion significantly increased soil bulk density but decreased soil structural stability and the concentrations and stocks of OC, N and P along the 0−70 cm soil profile. Additionally, most of the effects of erosion were enhanced with the intensity of erosion. However, OC, N and P were significantly higher at the deposition sites than at the either non-erosion or eroding sites in 15−70 cm soils, probably due to the burial of OC, N and P in deep soils of deposition sites. Moreover, the effects of converting forest to cropland on OC and N were greater than the effects of light erosion but smaller than the effects of moderate and heavy erosion in the top 30 cm soils. Therefore, erosion intensity should be carefully considered when disentangling the effects of converting natural ecosystem to managed ecosystem and soil erosion. [ABSTRACT FROM AUTHOR]

• Agricultural land experiences strong erosion in extreme rainstorms. • Concentrated flow is the main factor causing soil erosion in the agricultural land. • Bare soil should be protected with appropriate vegetation to reduce the erosion. • Drainage measures should be built to control soil erosion on agricultural land. • Agricultural land use and managements weaken soil erosion in heavy rain event. Elucidation of the soil erosion processes induced by extreme rainstorms provides better understanding and responding of agricultural system to global climate change. However, less attention has been given to the field investigation of soil erosion in the actual event of heavy rainfall. The purpose of this study was to assess the response capacity of agricultural land use and management to the heavy rainfall on northern rocky mountain area of China. (1) Compared with abandoned land and forest-grass land, the agricultural land experienced strong erosion. The erosion modulus (E m) of terrace land dominated by embankment failure (9490 t km−2) was less than that of sloped cropland dominated by rill/gully erosion (11,252 t km−2). (2) Concentrated flow was the main factor causing soil erosion, and almost all erosion occurred in the flow path. (3) Appropriate agricultural land use and management, such as terraced land, drainage channels, bio-embankments and plant pit cofferdam, could weaken soil erosion during extreme rainstorms. However, plastic film mulching aggravated soil erosion by rapidly forming concentrated flow. (4) To reduce the soil erosion on agricultural land under heavy rain event, we suggest managers should protect the bare soil with vegetation, conduct drainage measures, build high standard terraces in appropriate locations, and strengthen farmer training on agronomic measures. Our results could be applied to the response strategies of agricultural systems to global climate change. [ABSTRACT FROM AUTHOR]

The zoonotic transmission of hepatitis E virus (HEV) is mainly mediated by HEV genotypes 3 and 4, with domestic pigs serving as an important reservoir for both genotypes. In China, genotype 4 HEV is the primary prevalent genotype on pig farms. In this study, the prevalence of HEV infection in pig herds of Shaanxi Province was investigated. Serological testing detected anti-HEV antibody-positive pigs in five selected cities, with 13 of 17 farms harbouring at least one positive pig (76.47%). Within positive farms, the proportion of positive pigs ranged from 1.6% to 37.5%. Genetic detection analyses of faecal samples revealed that pigs in four cities and on nine of 17 farms were positive for sequences homologous to a partial ORF2-coding region of HEV (306 bp), as were 6 of 53 bile and 1 of 26 semen samples. Meanwhile, DNA coding for partial HEV ORF1 (1,080 bp) and a longer gene segment coding for partial ORF2 (1,594 bp) were successfully amplified from RNA isolated from pig semen from one HEV-positive pig. Sequence comparisons of partial ORF2 gene sequences showed that HEV isolates from Shaanxi Province shared the highest identity (81.4%-96.1%) with genotype 4 HEV. Phylogenetic tree analysis grouped these isolates into three subgenotypes (4d, 4h and 4i), with subgenotype 4i the predominant subgenotype. In addition, the HEV isolate from pig semen belonged to subgenotype 4i HEV based on phylogenetic trees constructed both using partial ORF1 and ORF2 gene sequences. In conclusion, HEV infection is endemic on pig farms of Shaanxi Province, China, and 4i is the predominant HEV subgenotype. More important, this is the first study demonstrating detection of HEV RNA in pig semen, suggesting that artificial insemination can transmit HEV in pigs., (© 2018 Blackwell Verlag GmbH.)

In China, thirteen species of tick-borne rickettsiales bacteria pathogenic to human have been reported in ticks and host animals, and human patients caused by them also has been identified. However, investigation for rickettsiales bacteria circulating in Xi'an wasn't performed although diseases resembling human diseases caused by these organisms have been found. In this study, domestic animals and ticks in Xi'an, China, were tested for the presence of rickettsiales bacteria pathogenic to humans. Besides A. ovis, a high prevalence of A. capra was observed suggesting a high public health risk exists. In addition, two novel Anaplasma species closely related to A. phagocytophilum were identified and formed distinct lineages in the phylogenetic trees, with more than 98.3% identities for rrs gene, while divergences up to 20.2% and 37.0% for groEL and gltA genes, respectively. Both of these two novel Anaplasma species were found to circulate in goats and further assessment of their pathogenicity is needed. Ca. R. jingxinensis, with potential pathogenicity, was also detected in H. longicomis ticks with high prevalence. However, other causative agents were not identified although they were distributed in other areas of China., Competing Interests: The authors have declared that no competing interests exist.

A blocking enzyme-linked immunosorbent assay (bELISA) was developed for the detection of immunoglobulin G antibodies against avian hepatitis E virus (HEV). In the bELISA, the coating antigen was a truncated protein containing C-terminal 268-amino acid region of ORF2 from an avian HEV strain isolated in China (CaHEV) and blocking antibody was a monoclonal antibody (mAb) 1H5 recognizing the epitope within amino acids 384-414 in the C-terminal 268-amino acid region. The concentration of blocking mAb 1H5 was determined as that yielded an OD450nm value of 1.0 for binding to the coating antigen and the antigen concentration and serum dilution were optimized using a checkerboard titration. A cut-off value of 20.7% at the mean percent inhibition plus 3 standard deviations was determined by testing 265 negative sera. The bELISA had a sensitivity of 98.3% by testing 116 positive sera from chickens infected experimentally with CaHEV and had no cross-reaction with other anti-avian virus antibodies. The compliance rates of the bELISA with indirect ELISA and Western blot were 83.7% and 93.3%, respectively, by testing 300 field chicken sera. These results suggested that the bELISA developed in this study can be used for detection of antibodies against avian HEV and showed high reproducibility compared with indirect ELISA and Western blot methods., (Copyright © 2014 Elsevier B.V. All rights reserved.)