Plant roots have been demonstrated effective in containing gully erosion in various environments. Related endeavors have mainly been devoted to quantify the total gully erosion or head retreat, yet few attempts been made to examine gully widening and its response to root traits. A typical forage grass, i.e., awnless brome (Bromus inermis Leyss.), was planted at five different row spacings of 10, 15, 20, 25, and 30 cm to simulate varying root densities in the loess hilly-gully region, and the channel widths at different slope sections upon field scouring were monitored at these treatments and also bare fallow plots (CK). Owing to the dominance of bank collapse over fluvial erosion, gully channels expanded intermittently rather than continuously at many slope sections. Compared to CK, growing grass at the row spacings ≥ 20 cm decreased both the distances and rates of channel widening. Further decreasing the row spacing, however, severe cantilever failure occurred due to large shear strength difference between surface and subsurface layers, resulting in stronger gully widening than at CK. Growing awnless brome at a row spacing of 20 cm was believed optimal in containing gully widening under current experimental conditions. According to the Pearson's correlation analysis, gully widening interacted most closely with the densities of root morphological parameters at the 10–20 cm depth. The corresponding length density was selected to establish the models for different widening characteristics, which varied among slope sections. As the root density increased, both the widening distance and rate decreased exponentially at the middle section; whereas at the upper section, the widening distance increased linearly, and the mean widening rate exhibited a significant decreasing-then-increasing trend.

Gully erosion is a significant soil erosion process worldwide, especially in semi-arid regions. Representing the most severe erosion phase, gully development poses a major threat to soil quality and land productivity, and to the achievement of multiple sustainable development goals (SDGs). To effectively prevent and control gully erosion, many models have been developed to predict the locations of gully initiation, among which the topographic threshold has been most frequently applied. Approximating the erosive force by a combination of the local slope (S) and upslope drainage area (A), gully erosion is expected to initiate where the erosive force of flowing water exceeds the erosion resistance. This threshold condition can be expressed as SAb = k, in which both b and k are constant coefficients varying with environmental conditions. During recent decades, significant progress has been made in the measurements of both S and A, and the determination of S-A thresholds, resulting in an increased number of S-A datasets and thresholds. The objective of this study was to systematically review and evaluate the existing methods for S-A threshold derivation and data collection, and to assess the effects of climate, lithology, soil texture and land use on gullying threshold based on a total of 127 S-A datasets comprising 5,302 S-A pairs retrieved from 55 publications. In accordance with the geographical distributions of gully erosion, the S-A thresholds were mainly investigated in the temperate climate, sedimentary lithology dominated by marls and loess, loamy soils, and on the agricultural lands especially croplands. A total of 15 approaches have been developed to determine the S-A threshold, among which the orthogonal regression (OR) method calculating the lower limit of the 95% prediction confidence interval around the OR trendline was believed the optimal in general. Applying this method to all the S-A pairs retrieved, a global threshold was generated as SA0.269 = 0.014. Working on both the S-A dataset and pair levels, the area exponent b was found to be primarily affected by climate and lithology, and the threshold coefficient k to be strongly influenced by land use. The rapid development of GIS technology has remarkably increased the numbers of S-A datasets and data pairs, and the traditional field survey techniques have been replaced by high-resolution DEMs obtained from, for example, real-time kinematic (RTK) GPS and unmanned aerial vehicle (UAV) photogrammetry. Future research efforts are still needed to further enrich S-A data in different environments, to standardize the acquisition procedure for S and A, and to explore advanced methods for S-A threshold determination.

Straw incorporation is a tillage practice that has been increasingly adopted to sustain soil quality and combat soil erosion in the black soil region of northeast China. Most of the previous studies in this region focused on the impact of incorporation rate, yet the effects of straw length on runoff and sediment characteristics there remain obscure. In this study, maize straw segments of four different lengths (2, 5, 10, 20 cm) were incorporated at a constant rate of 6 t hm(-2) into the plow layer of a cultivated black soil, and a bare black soil without straw application was used as the control (CK). Simulating rainfalls at two intensities (60, 90 mm h(-1)) and two slopes (3 degrees, 6 degrees), straw incorporation was found to generally delay runoff generation, reduce surface runoff, decelerate surface flow, and impair soil erosion compared to CK. However, the runoff and sediment characteristics responded differently to straw length (SL). As SL increased, the runoff initiation time increased exponentially, the total runoff depth (RD) decreased linearly, but the mean flow velocity initially decreased and then increased. The mean sediment concentration (SC) also exhibited decreasing-then-increasing trends with SL except under the 90 mm h(-1) rainfall intensity and 6 degrees slope combination (R90-S6). The relationships of the total sediment yield (SY) with SL basically followed those of SC, which were significantly fitted by the quadratic functions (p < 0.05) and the optimal SL corresponding to the least SY was estimated at similar to 12 cm. The only exception was spotted under R90-S6 presenting relatively consistent SCs, where similar to RD, SY exhibited a linearly decreasing trend with SL. In this case, the longest straw segments of 20 cm under investigation were believed optimal. These findings demonstrate the critical role of straw length and reveal its varying effects on runoff and sediment characteristics, and hold practical implications for agricultural management on local sloping farmlands.

The Ordos Plateau lies on the northwest margin of the East Asian monsoon region as well as the farming-pastoral ecotone in northern China, with a wide distribution of nebkhas. The formation and development of nebkhas in this region are closely related to natural envi ronmental conditions and human activities. However, the processes of nebkhas formation and development under natural and anthropogenic influence still remain unclear. In this study, four typical nebkhas in the Ordos Plateau were selected after detailed field investigations. Chronology and sedimentary features of the formation and development of nebkhas were studied based on optically stimulated luminescence (OSL) dating, lithology, grain size, etc. The results demonstrated that modern nebkhas had formed since at least ~0.59 ka in the southwest of the Ordos Plateau, followed by the middle region, at least ~0.34 ka, and later in the south and north regions, at least ~0.10 ka. There were thin layers of weakly-developed paleosols at ~0.32-0.25 ka, peaks in the silt and fine sand content and lower deposition rates, about 0.37-0.46 cm/a, indicating a relatively humid climate and weak aeolian activities. After ~0.10 ka, aeolian activities intensified and the nebkhas widely developed with a higher deposition rate, ~0.45-5.21 cm/a. Nebkhas in the study region developed primarily over paleo-channels or paleosol layers. Very fine sand and fine sand were dominant composition on grain size of nebkha sediments; saltation was a main means for the particle movements, indicating near-source accumulation for nebkha sediments. In recent decades, local farmers are used to adding nebkhas deposits to the soil of irrigation areas to improve the soil quality and alleviate soil salinization. Such agricultural activities, together with land reclamation, have accelerated the demise of the nebkhas in the Ordos Plateau.

Soil erosion is a crucial process leading to soil organic carbon (SOC) and total nitrogen (TN) redistributions in the topsoil in agricultural ecosystems, yet it remains ambiguous how the spatial variability of topsoil SOC and TN respond to soil erosion. The objective was to characterize the spatial structures of topsoil SOC, TN and their stochiometric ratio, and to disentangle their spatial relationships with soil erosion in a landscape. On a toposequence spanning similar to 3,500 m in the black soil region of northeast China, soil erosion rate (ER), and SOC, TN and the C/N ratios at the depths of 0-10 and 10-20 cm were investigated in an interval of 40 m. Unlike the highly variable ER presenting a long-range exponential structure, both the contents and stocks of topsoil SOC and TN were moderately variable and displayed spherical structures with much shorter correlation ranges between 1,000 and 1,400 m. The C/N ratios were even less variable, and exhibited nearly random distributions. Except for the C/N ratio at 0-10 cm depth, all variables were significantly negatively associated with ER at the scale of investigation (p < 0.05), as erosion tends to remove the fertile topsoil, especially the fine particulate organic matter rich in C, and to promote SOC decomposition via aggregate disintegration. The corresponding correlation coefficients ranged from -0.260 to -0.527. Applying multivariate variational mode decomposition (MVMD), however, insignificant and even significantly positive correlations were detected at different spatial scales between some variables and ER. The wavelet coherency corroborated the scale-dependent relationships of each variable with ER, and specified the sections displaying various correlations. These findings demonstrate the intricate spatial relationships of topsoil C and N with erosion, and hold important implications for sustainable agricultural management.

Soil erosion is a crucial process leading to lateral redistributions of surface soil organic carbon (SOC) and total nitrogen (TN). However, its role in the profile distributions of SOC, TN, and their stoichiometry remains unclear. The objective was to evaluate the impact of soil erosion on both the horizontal and vertical distributions of SOC, TN, and the C/N ratio along a cultivated hillslope. On a typical slope farmland in the black soil region of northeast China, the mean annual soil erosion rate (ER) and the profile distributions of SOC, TN, and the C/N ratio were investigated at different slope positions. Both SOC and TN decreased exponentially with depth at each position, except the foots experiencing limited SOC decomposition due to elevated soil moisture and prone to being covered with sediment eroded upslope. The surface SOC and TN at the foots, as a consequence, could be similar to or even lower than those underneath and at the other positions. Given such complexity, no significant correlation was manifested between ER and either surface content (p > 0.05). Nevertheless, the depletion rates of both SOC and TN significantly positively interacted with ER (p < 0.05), as soil erosion tended to enhance the contrasts of soil nutrients thus biomass between the surface and subsurface soils. The C/N ratios of the plough layer were relatively consistent among the slope positions, and no statistical interaction was detected between the mean ratio and ER (p > 0.05). As soil depth increased, however, the C/N ratio changed remarkably at most positions, on account of the presence of the plow pan and/or the deposition of sediments over the original soils.

Slope aspect is a significant terrain attribute influencing soil physical and chemical processes. Yet its impact on soil quality and erosion has rarely been studied on gently sloping farmlands. The objective was to evaluate the effects of slope aspect on soil quality and its response to soil erosion in the black soil region of northeast China, a temperate environment featuring gently sloping farmlands. Over a nearly north-south symmetric sloping farmland spanning similar to 3500 m, fifteen soil physical and chemical properties were investigated at every 40 m, and an integrated soil quality index (SQI) was calculated combining principal component analysis and scoring functions. The mean annual erosion rate (ER) was estimated using the cesium-137 tracing technique. Compared to the south-facing slope, the north-facing slope possessed significantly lower pH and higher saturated hydraulic conductivity, sand content, and almost all the essential nutrient contents, therefore overall better soil quality (p < 0.05). No statistical difference was spotted in ER between the two slopes (p > 0.05); however, erosion was found to deteriorate soil quality via distinct pathways. On the north-facing slope, erosion affected SQI predominantly through its negative impact on soil organic carbon content and wet-aggregate stability, and conservation tillage practices were suggested. However, on the south-facing slope, the detrimental influence was primarily driven through the depletion of soil nutrient contents, particularly available phosphorus and total nitrogen, and contour tillage and hedgerows were strongly recommended. These findings hold important practical implications for agricultural management in temperate environments.

Environmental Variability Selection (EVS) is hypothesized for the emergence of early Homo (H.) sapiens with small lithic tools in Africa. Yet, it is unclear how the EVS works when a special hominin group with advanced small lithic tools evolved from the Asian H. erectus with expedient core and flake industry. Lantian loessland in southern Chinese Loess Plateau in North China preserves continuous and concentrated hominin fossil, faunal, pollen, stone tool, paleoclimate, and landform records for last 2 million years (Ma) and is an ideal place to test this hypothesis. We reanalyzed delta 13C values of soil organic and inorganic carbon from 2 Lantian loess-paleosol records to partition seasonal climate and habitat changes with synthesized lithic, faunal, and pollen data to seek cluses. We found that Lantian Gongwangling and Chenjiawo H. erectus adapts to woodland-forest habitats, manufacturing Mode 1 stone artifacts foraging subtropical animals in warm and Paleoarctic animals in cool seasons on the low and medium-high rolling loessland, while more advanced Dali hominins adapt to certain steppe-shrubland habitats manufacturing diverse small-sized lithic tools to forage more open-habitat animals in all seasons on hilly landforms. We propose that co-evolution of seasonal habitat variability and changing local landforms in 2.0-0.2 Ma advances Dali hominin's cognitive capacity for strategically using landform morphology for subsistence and manufacture small stone tools for intercepting high fluxes of seasonal resources on highly variable loessland. Seasonal landscape variability and landform evolution is the key in the EVS for the evolution from Asian H. erectus to a more advanced hominin group or species.

Aeolian-fluvial processes are crucial in shaping landforms. Despite the advancements in understanding the sedimentary processes of aeolian-fluvial interactions, the sedimentary patterns of these interactions are complex in spatiotemporal scale, and the records of Holocene small-scale aeolian-fluvial interaction sedimentary is insufficient, especially in the Tibetan Plateau region. Therefore, this study focuses on analyzing the sedimentary patterns of aeolian-fluvial interactions and their response to climate change in the Paiku Co basin of the southern Tibetan Plateau (TP). Through the examination of aeolian-fluvial sequences, Optically Stimulated Luminescence (OSL) dating is utilized to establish a chronological framework. Furthermore, proxy indices are explored to identify potential sediment models and their reactions to climate change. The findings indicate that fluvial activity predominated during a relatively warm and wet period around 5.1-4.6 ka, while thicker aeolian sands accumulated extensively during 4.6-4.1 ka as the climate transitioned to cold and dry conditions. On a millennial scale, the aeolian-fluvial interaction sedimentation is characterized by alternating deposition of clay layers and medium to fine sand. This sedimentation pattern is predominantly influenced by climate change. Overall, the findings shed light on the complex coupling between aeolian and fluvial processes in response to past climate changes, which has important implications for understanding the landscape evolution and environmental changes in this sensitive high-altitude region.

Aeolian sediments accumulated along the desert-loess transition zone of the Tengger Desert include heterogeneous textures and complex component structures in their grain-size distributions (GSD). However, the sources of these aeolian sediments have not been resolved due to the lack of large reference GSD sample datasets from adjacent regions that contain various types of sediments; such datasets could be used for fingerprinting based on grain-size properties. This lack of knowledge hinders our understanding of the mechanism of aeolian dust releases in these regions and the effects of forcing of atmospheric circulations on the transportation and accumulation of sediments in this region. In this study, we employed a multi-scale grain-size analysis method, i.e., a combination of the single-sample unmixing (SSU) and the parametric end-member modelling (PEMM) techniques, to resolve the component structures of sediments that had accumulated along the desert-loess transition zone of the Tengger Desert. We have also analyzed the component structures of GSDs of various types of sediments, including mobile and fixed sand dunes, lake sediments, and loess sediments from surrounding regions. Our results demonstrate that the patterns observed in coarser fractions of sediments (i.e., sediments with a mode grain size of >100 μm) from the transition zone match well with the patterns of component structures of several types of sediments from the interior of the Tengger Desert, and the patterns seen in the finer fractions (i.e., fine, medium, and coarse silts with a modal size of <63 μm) were broadly consistent with those of loess sediments from the Qilian Mountains. The deflation/erosion of loess from the Qilian Mountains by wind was the most important mechanism underlying the production of these finer grain-size fractions. The East Asia winter monsoon (EAWM) played a key role in transportation of the aeolian dust from these source regions to the desert-loess transition zone of the desert.

Nebkhas, as special biologically mediated aeolian landforms, play an important role in indicating regional aeolian activities and aeolian environmental changes. The Ordos Plateau is located in arid and semiarid regions of northern China that have a wide distribution of Nitraria tangutorum nebkhas. There are few chronological records of nebkha formation, so the history of the formation and evolution of nebkhas in the plateau is still unclear. In addition, the optically stimulated luminescence (OSL) dating method, which has been widely used in the dating of Holocene aeolian sediments, has not yet been applied to the dating of nebkha sediments in the Ordos Plateau. In this study, OSL methods were used to discuss the formation age and relevant aeolian activities of Nitraria tangutorum nebkhas in the Ordos Plateau. The results demonstrated that (1) the coarse-grained quartz OSL signals of nebkha sediments were insensitive and thus were inapplicable by the single aliquot regenerative (SAR) protocol. (2) The luminescence characteristics of the K-feldspar fraction and internal checks of the post-infrared infrared-stimulated (pIRIR) dating indicated that the pIR(50)IR(170) protocol with 200 degrees C of preheating was applicable for D-e determinations of nebkha sediments. (3) The residual doses of the pIRIR(170) signals ranging from 0.02 to 0.14 Gy should be considered when calculating D-e values. (4) Bayesian age-depth models were used for the Nitraria tangutorum nebkha sedimentary sequences. The formation of nebkhas occurred during a relatively dry climate period accompanied by strong aeolian activity. That similar to 0.38 ka was the main growth period of Nitraria tangutorum nebkhas. This study is the first report of the formation age of nebkhas of more than one hundred years in the region.

Saturated hydraulic conductivity (Ks) is highly variable in both space and time. Compared to its spatial variability, however, the temporal Ks variability has rarely been studied or taken into account in the hydrological modelling. The objectives were to characterize the slope-scale temporal variability of Ks and to diagnose the primary factors regulating Ks 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 Ks, 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 Ks 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 Ks 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 Ks through their influence on BD and/or other factors. These findings demonstrate the strong temporal variability of Ks throughout the maize growing season and intricate interactions of Ks 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.

Soil erosion is a major cause of soil degradation, leading to soil quality deterioration. The resulting alternation of soil properties would in turn change the soil's responses in subsequent soil erosion events later, which, however, has rarely been studied. The objective was to examine the effects of such erosion-induced degradation on subsequent soil erosion and sediment size distribution of a cultivated black soil under heavy rainstorms. The plough layers of the black soil that had suffered from 0, 10, 30, 50, and 70 years of soil erosion in northeast China were artificially constructed, corresponding to five erosional degradation levels of none, slight, moderate, severe, and very severe degradations, successively. A simulated heavy rainfall at the 75 mm h(-1) intensity was performed, and runoff and sediment samples were collected every 6 min and analyzed for particle size distribution. Owing to the increasingly coarse source soil and thereby enhanced hydraulic conductivity, the steady-state runoff rate decreased from 1.06 to 0.77 mm min(-1), as the degradation level increased from none to very severe degradation. However, the fine-textured noneroded soil had a better water retention capacity, which decreased runoff, especially at the beginning of the rainfall. The maximum runoff in total, that is, 103.61 mm, was consequently observed in the slightly degraded soil. The sediment concentrations and yields here were also significantly greater than those of the other treatments (p <0.01), suggesting a relatively higher soil erodibility. Sediment sorting was observed at each treatment especially during the first half of the rainfall, except for the slightly eroded soil where the elevated runoff was believed sufficient to equally transport different-sized particles. The clay particles were enriched in the sediments eroded from the non- and moderately degraded soils, as the corresponding enrichment ratios (ERs) were typically above 1. Whereas for the severely and very severely degraded soils, ERs were around 0.5, indicating considerable depletion of these fine particles. These results demonstrate the diverse erosional responses of the soils exhibiting varying erosion-induced degradation levels and hold important implications for agricultural management and soil and water conservation in the black soil region of northeast China as well as other similar regions.

Abstract Reliable estimates of saturated hydraulic conductivity (Ks) are usually difficult to obtain, as Ks is regulated by a variety of soil processes acting at different spatial scales that may obscure each other's impacts. We hypothesized that these scale‐specific relationships could be well characterized with the aid of the noise‐assisted multivariate empirical mode decomposition (NA‐MEMD), thereby serving as a solid foundation for an accurate Ks prediction. The objective was to evaluate whether the incorporation of NA‐MEMD could improve the estimation of Ks based on the multiscale associations it unraveled. On a typical slope transect of 860 m in the black soil region of northeast China, Ks, mollic epipedon thickness, bulk density, soil organic carbon content, total (ϕ) and effective porosities (ϕe), and particle size distribution were investigated at every 20 m. Prior to NA‐MEMD, Ks was most strongly correlated with ϕe, and the linear regression models based on ϕe solely were satisfactory for Ks estimation at the scale of investigation. Adding other predictors significantly improved Ks prediction in calibration, but impaired it in validation. Upon decomposition by NA‐MEMD, Ks was found to be significantly associated with each attribute at two scales of oscillation at least. Summing up the estimates of each Ks component derived from the properties at the equivalent oscillation scales, the results outperformed the traditional multiple linear regressions made at the investigation scale, when the same sets of predictors were used. The application of NA‐MEMD, moreover, could save the tedious measurements of ϕe and ϕ. Excluding these two porosity‐related properties, Ks estimates obtained by incorporating NA‐MEMD were statistically similar or even better than those involving them before NA‐MEMD. These findings demonstrate the great potential of NA‐MEMD in untangling scale‐dependent relationships of Ks with various processes and hold important implications for future estimations of Ks and other hydraulic properties in the black soil region of northeast China and similar regions.

Sediment deposition is one of the most significant processes in small watersheds characterized by gentle long hillslopes in the black soil (Mollisol) region of Northeast China, as indicated by severe ephemeral gully and gully erosion on hillslopes and very low sediment concentrations in river systems. Few reviews have been conducted to summarize the related research in this region. The objectives of this review were to identify the potential factors influencing sediment deposition, review related studies, and propose future research needs in the black soil region of Northeast China. Sediment deposition is controlled by the deficit between sediment transport capacity of flow and sediment load. Hence, all factors affecting flow transport capacity and sediment load directly affect sediment deposition. For a specific small watershed, the change in slope gradient along the flow path is the key factor affecting sediment deposition. Shelterbelts, ridge tillage systems, terraces, grass strips, road distribution, ponds and reservoirs, and land -use patterns also influence the spatial distribution and rate of deposition. The trace method has been widely used to quantify sediment deposition in this region. The results of cesium -137 (137Cs), lead -210 (210Pb), and magnetic susceptibility reveal that serious deposition occurs on the back and foot slopes. Distinct deposition occurs in front of contour shelterbelts. Future studies should focus on the methodology, spatial and temporal variations, dominant influencing factors and their mechanisms, and the potential effects on land productivity within specific small watersheds and across the black soil region. This review provides insights into the sediment deposition process in small watersheds characterized by gentle, long hillslopes.

Sediment deposition is one of the most significant processes in small watersheds characterized by gentle long hillslopes in the black soil(Mollisol)region of Northeast China,as indicated by severe ephemeral gully and gully erosion on hillslopes and very low sediment concentrations in river systems.Few reviews have been conducted to summarize the related research in this region.The objectives of this review were to identify the potential factors influencing sediment deposition,review related studies,and propose future research needs in the black soil region of Northeast China.Sediment deposition is controlled by the deficit between sediment transport capacity of flow and sediment load.Hence,all factors affecting flow transport capacity and sediment load directly affect sediment deposition.For a specific small watershed,the change in slope gradient along the flow path is the key factor affecting sediment deposition.Shelterbelts,ridge tillage systems,terraces,grass strips,road distribution,ponds and reservoirs,and land-use patterns also influence the spatial distribution and rate of deposition.The trace method has been widely used to quantify sediment deposition in this region.The results of cesium-137(137Cs),lead-210(210Pb),and magnetic susceptibility reveal that serious deposition occurs on the back and foot slopes.Distinct deposition occurs in front of contour shelterbelts.Future studies should focus on the methodology,spatial and temporal variations,dominant influencing factors and their mechanisms,and the potential effects on land productivity within specific small watersheds and across the black soil region.This review provides insights into the sediment deposition process in small watersheds characterized by gentle,long hillslopes.

在黄土高原六道沟小流域选择 7 条代表性切沟,以激光扫描法(laser scanning,LS)和实时动态差分(real-time kinematic,RTK)GPS的测量结果为基准,评估运动恢复结构(structure from motion,SfM)摄影测量法对切沟及切沟侵蚀的测量精度.与LS和RTK GPS相比,SfM摄影测量法所测各切沟DEM总体差异不大,平均高程差值为-0.162～0.436 m;SfM摄影测量法对切沟长度、表面宽度、周长和面积的测量精度较高,相对误差基本不超过±7%;所测深度和体积的相对误差较大,介于-37.4%～18.0%.与RTK GPS所测切沟侵蚀相比,SfM摄影测量法测得的切沟侵蚀空间分布和形态参数变化均十分接近.研究结果证实,SfM摄影测量法可作为一种高精度测量方法应用于黄土高原的切沟和切沟侵蚀监测.

Straw mulching has been widely demonstrated as a useful practice for soil and water conservation, but its effectiveness in controlling rill erosion has rarely been systematically studied. The objective of the current study was to evaluate the effects of straw mulching on rill development and rill network evolution. A cinnamon soil was mulched with corn straw segments at five different rates of 0, 2.1, 4.2, 6.3 and 8.4 t ha-1, to attain the surface coverages of 0%, 10%, 20%, 30% and 40%, respectively, and received four 30-min simulated rainfalls at the intensity of 90 mm h-1. The structure from motion (SfM) photogrammetry was applied to measure soil surface elevation changes upon each rainfall. Straw mulching was found to retard runoff initiation, but decreased soil losses were typically acquired at the mulched treatments with 20% or more straw coverages. Nevertheless, this conservation effect did not monotonically increase with mulching rate, because a larger number of straw segments were more likely to induce rill erosion via surface flow convergence, thereby increasing total soil loss. Straw mulching also changed the course of rill development. Head retreat dominated rill erosion at the control without mulching throughout the entire experiment, suggesting an early stage of rill erosion. With the straw segments around and at the bottom, the initially equivalent contributions by headcutting, bed scouring and sideward erosion quickly shifted to the predominance of bed incision and then to sidewall expansion, succes-sively. The rapid transition of rill erosion subprocess in this way, together with the dendritic and stabilized networks, indicate a mature stage of rill development by the end of the experiment. The rill depths and main channel widths, as a consequence, were typically smaller at the mulched treatments. These findings demonstrate the effectiveness of adequate straw mulching in stabilizing rill network in addition to reducing soil erosion at the plot scale, and hold important implications for agricultural management in slope farming systems.

[Objective] The particle size distributions (PSD) of different soils measured by scanning electron microscopy (SEM) and by the pipette method (PM) in the water erosion region of China was compared in order to provide a reference for the determination of typical soil PSDs and their applications in soil erosion models. [Methods] Five typical soils corresponding to the five water erosion subregions of China (i.e., black soil, cinnamon soil, loess, purple soil, and red soil) were collected and analyzed by PM and SEM. Specifically, soil suspensions of different size classes obtained by PM (i.e., < 100, < 53, < 20, < 10, < 5 and < 2 μm) were measured using SEM. The PSD results determined by PM and SEM were compared and the causes for their difference were determined. [Results] For most soil suspensions obtained by PM, particles larger than the corresponding size classes of the suspensions were detected by SEM. As the size classes of soil suspensions decreased, both the count and volume fractions of the corresponding sizes, as measured by SEM, decreased. For the suspensions < 100 μm, the particles of the black, cinnamon, and purple soils fell mainly in the 20—53 μm class, resulting in relatively lower values of SEM-derived mean volume diameter (MVD). In contrast, the primary size classes of the loess and red soil were 20—53 and 53—100 μm, leading to larger MVD. Little difference was observed in the PSDs of loess between PM and SEM for the suspension < 100 μm. Compared with SEM, PM overestimated the clay fractions < 2 μm of the other soil samples, and underestimated the size fractions of 20—53 μm for the black, cinnamon, and purple soils, as well as the fractions of 20—100 μm for the red soil. As a result, the PM-derived mean weight diameters (MWD) were smaller than the SEM-derived MVD for all of the investigated soils. Additionally, the PSD discrepancies between the two analytical methods shifted the textural classes of 84.6% of the total soil samples. Converting the PM-derived PSD with the optimal S-curve models, the proportion of the samples with different textural classes due to PSD analytical method decreased to 61.5%. [Conclusion] Based on the SEM results, PM tended to misestimate the PSDs of all of the five typical soils in the water erosion region. The PSD differences between the two methods varied with soil type and were mainly related to soil mineral composition and clay mineral types.

实验室综合管理信息系统已是国家重点实验室下设测试分析中心实验室管理的必要工具,可实现全方位、全流程实验室精细化管理.地表过程与资源生态国家重点实验室的综合管理系统是涵盖实验室资源管理、人员管理、安全管理、数据管理的一站式服务和管理平台,实现了规范化、智能化和流程化的实验室管理机制,显著提高了实验室管理水平和工作效率.对实验室综合管理系统运行统计数据进一步分析,并对实验室管理系统的运行状况与问题进行总结,为实验室管理起到了指导作用,并且为后续的实验室综合管理系统建设提供宝贵经验.