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Preferential flow plays a vital role in infiltration processes in structured soil. However, knowledge of preferential flow in colluvial deposits of Benggang remains limited. In this study, three typical colluvial deposits with different formation times were selected. The formation times of colluvial deposits A, B and C increased in sequence. Water infiltration in colluvial soil was visualized through Brilliant Blue dye experiments (a total of 90 photos from the dyed soil profiles). The dye morphological characteristics of preferential flow were analysed, and the influencing factors were explored. The dye morphological parameters confirmed the occurrence of preferential flow in the colluvial deposits. The dye coverage of colluvial deposit A was the greatest (61.12%), followed by colluvial deposits B (50.41%) and C (46.81%). The matrix flow depth, preferential flow fraction and length index of colluvial deposits A and B were greater than those of colluvial deposit C. Preferential flow was more notable in colluvial deposits A and B than in colluvial deposit C. The migration process of dyed water varied spatially. There were more preferential flow paths at a 10 cm horizontal width. In addition to the bulk density and saturated hydraulic conductivity, the soil particle composition, especially the gravel content (r = 0.740), was closely related to the observed dye coverage. According to the principal component analysis results, the soil particle composition imposed the greatest influence on the formation of preferential flow in the colluvial deposits, with a contribution of 45.24%. The results provide a theoretical reference for explaining the mechanism of soil infiltration processes and a systematic basis for the treatment of colluvial deposits. [ABSTRACT FROM AUTHOR]

The rehabilitation of diverse and three‐dimensional forest vegetation patterns is crucial for preventing forest degradation and improving soil fertility. However, the relationship between soil microbial community and soil fertility was not clear. To accurately assess the capability of vegetation restoration measures on the real impact on degraded soil ecosystems. We selected three vegetation rehabilitation models of degraded Pinus massoniana forests in typical soil erosion areas in China as the research objects, with untreated bare land as the control. All three vegetation construction patterns increased the abundance and diversity of soil bacteria and fungi, thereby enhancing the stability of the soil ecosystem. Additionally, the vegetation rehabilitation models also altered the community structure of soil bacteria and fungi in the degraded P. massoniana forests. The pH and soil fertility index (IFI) were the main factors leading to variations in the community structure of the soil bacteria and fungi. Among them, the grass‐planting model showed a significantly greater improvement in the soil fertility of degraded P. massoniana forests than the shrub‐planting and arbor‐planting models. Furthermore, Ascomycota, Basidiomycota, and Glomeromycota exhibited the most significant response to IFI, indicating their potential as indicator microorganisms for soil fertility changes. The improvement in soil fertility in degraded P. massoniana forests was influenced primarily by the increase in urease activity (S‐UE) according to the vegetation rehabilitation models (84.20%, p = 0.000). In conclusion, the grass‐planting system effectively improved the soil ecosystem quality of degraded P. massoniana forests in southern erosion‐prone areas of China and was suitable for further application. [ABSTRACT FROM AUTHOR]

Land use and rainfall are two important factors affecting soil erosion processes. The red soil region of southern China is a representative region with high rainfall amounts and rapidly changing land use patterns where the water erosion process is sensitive to changes in land use and rainfall. To comprehensively understand the water erosion response to land use and rainfall in this region, a 6-year in situ experiment based on eight plots (bare land and seven typical land uses) was conducted from 2015 to 2020. The 320 rainfall events were divided into 4 types, and there were 3 main rainfall types. The runoff of different rainfall types was primarily determined by the rainfall amount, while the soil erosion of different rainfall types was primarily determined by the rainfall intensity. High-intensity rainfall contributed the most to both total runoff and soil erosion. Compared with bare land, the seven typical land uses reduced runoff and soil erosion by more than 75%. Grassland, cropland, and forest with low vegetation coverage experienced high runoff and soil erosion, while shrubland most effectively reduced runoff and soil erosion. The combination of land use and rainfall type significantly affected the annual average runoff depth, soil erosion modulus, and soil loss coefficient. Rainfall types can change the relationship between runoff and soil erosion for different land uses. The runoff and soil erosion of bare land were highly correlated with rainfall characteristics, while vegetation weakened this relationship under short- or moderate-duration rainfall. To effectively reduce water erosion, high-intensity rainfall should receive special attention, and all land uses should ensure that vegetation is well developed, especially understory vegetation. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV)-based nap-of-the-object photogrammetry techniques can be utilized to periodically monitor the erosion of nearly vertical cliffs. However, the broader applicability of such techniques is hindered by the necessity of deploying multiple ground control points around collapsing walls. This study aims to accurately assess Benggang erosion before and after the rainy season by analyzing the optimal flight proximity distance using close-range photogrammetric techniques. The assessment centers on positioning accuracy, point cloud data, and digital surface model (DSM) data. Nap-of-the-object photogrammetry techniques are integrated with control-free image methods to conduct aerial surveys of Benggang, generating high-resolution three-dimensional (3D) DSMs. The feasibility of this control-free-image-based nap-of-the-object photogrammetry technique is evaluated based on positioning accuracy and measurement errors, comparing the generated DSMs with real-time kinematic (RTK) measured coordinate data. The results indicate that a flight proximity distance of 20 m is optimal for obtaining data in the Benggang area using control-free-image-based nap-of-the-object photogrammetry. This scheme yields an average reprojection error of approximately 0.01 pixels in data processing before and after rainfall, showing strong consistency in the spatial distribution of the two-stage 3D models. The mean absolute error in planar accuracy is between 0.01 m and 0.02 m, and that in elevation accuracy is approximately 0.03 m, with the lowest errors reaching the millimeter level. Therefore, control-free images combined with nap-of-the-object photogrammetry techniques can meet relevant demands for monitoring landslide erosional areas, providing technical support for extensive, safe, and efficient Benggang erosion monitoring. [ABSTRACT FROM AUTHOR]

Soil bacterial communities play a crucial role in the evaluation of soil ecosystem stability. Vegetation restoration is a key determinant of soil bacterial communities in areas affected by soil erosion. However, it remains unclear how the structure and diversity of soil bacterial communities vary with soil depth. In this study, we collected soil samples from 0 to 10 cm, 10 to 20 cm, 20 to 30 cm, and 30 to 40 cm depths in vegetation restoration sites located in typical soil erosion areas in China. We compared and analyzed the differences in bacterial community characteristics among different soil depths, using untreated areas as controls. Compared to the untreated areas, the abundance of soil bacteria in the 0–10 cm, 10–20 cm, and 20–30 cm depths of the vegetation restoration sites increased by 1.63, 1.04, and 1.29 times, respectively. Furthermore, vegetation restoration enhanced soil bacterial diversity at the 0–10 cm, 10–20 cm, and 20–30 cm depths. Soil organic carbon (OC) was the main explanatory factor (53.50%, p = 0.000) for the decrease in soil bacterial diversity with soil depth. Additionally, after vegetation restoration in soil erosion areas, the dominant bacterial community composition shifted from Chloroflexi to Actinobacteria at the 0–10 cm, 10–20 cm, and 20–30 cm depths and to Proteobacteria at the 30–40 cm depth. The differences in soil bacterial communities among different soil depths were primarily driven by soil total nitrogen (TN) content, which explained up to 34.5% of the variation. In conclusion, in the subsequent management of vegetation restoration sites, increasing OC and TN content can enhance soil bacterial diversity, improve bacterial community composition, and ultimately enhance the stability of soil ecosystems. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties significantly affect the occurrence and development of collapsing gully walls. The effect of temperature on the hydraulic properties of soil in collapsing gully walls remains unclear. In this study, the hydraulic properties of the red soil layer, the sandy soil layer and the detritus layer in a collapsing gully wall were investigated using the filter paper method, and the soil water retention curves of the different soil layers at 25 and 40 °C were determined. The aim of this study was to investigate the impact of temperature on the soil hydraulic properties of different soil layers in collapsing gully walls. The study found that when the water content in the red soil layer and sandy soil layer exceeded 20% and in the detritus layer exceeded 10%, the soil's matric suction significantly decreased as the temperature increased from 25 to 40 °C. Additionally, the parameters of θ s , α , n and m all exhibited a decreasing trend, and the soil water content in the detritus layer was primarily influenced by the temperature change, which resulted in a decrease of 38.10%. The unsaturated hydraulic conductivity of the detritus layer exhibited higher values than that of the sandy layer and red soil layer under identical temperature conditions. Moreover, the unsaturated hydraulic conductivity of the red soil layer, sandy soil layer and detritus layer increased with increasing temperature. It was observed that the unsaturated hydraulic conductivity of the detritus layer increased by 0.18 cm h−1 at a soil water content of 44%. This increase in conductivity was more pronounced than the corresponding changes in the red soil layer and sandy soil layer. An elevated temperature caused the water-holding capacity of the different soil layers of the collapsing gully wall to decrease and the unsaturated hydraulic conductivity to increase. However, the influence of the clay particle content within the soil of the collapsing gully wall rendered the temperature effect more distinct. Therefore, the destabilizing deformation of the soil in the collapsing gully wall during the summer under high temperatures and precipitation may have played a key role in its collapse. [ABSTRACT FROM AUTHOR]

Soil cracks thoroughly affect the soil shear strength, which is a critical parameter in the analysis and modeling of slope stability. However, the relationship between soil cracks and shear strength in collapsing gullies remains inadequately studied. In this study, soil collected from collapsing gully areas was used to quantitatively investigate the parameters of soil desiccation cracks and the effects of soil cracks on shear strength. The results showed that the development degree of soil cracks increased gradually with decreasing soil water content. During desiccation, surface crack evolution was dominated by the formation of more cracks when soil water content was higher than 20%, and then experienced crack width extension for at lower soil water content. Three-dimensional crack analysis showed that cracks in the undisturbed soil of the red soil layer were very densely developed, and the cracks rates were all greater than 9%. Soil water content and cracks controlled the shear failure characteristics under triaxial compression, and the characteristics of soil shear failure can be summarized into three categories: composite softened soil, ideal elastoplastic soil, and curve-softened soil. The shear strength (τc) of undisturbed red soil samples had significant negative correlations with the crack rate (CR), total crack length (CL), crack connectivity (CC), and crack fractal dimension (FD). Linear fitting analysis showed that the effect of cracks on soil shear strength could be described as follows: τc = 1548.8−22.4 × WR−2.67 × CR−4.65×CC, which is helpful for the numerical simulation analysis of the stability of collapsing gully walls. [ABSTRACT FROM AUTHOR]

Assessing the distribution and risks associated with the soil lead content in the Tieguanyin tea plantations of Anxi County is critical, given the county's significance as the primary Tieguanyin tea production area in Fujian Province. This study examined the distribution characteristics of soil lead in Anxi County's tea plantations according to the Kriging spatial interpolation of the parameters of the semivariance function of the exponential model. Moreover, the sources of lead content were analyzed, considering geological backgrounds and anthropogenic influences. Ecological risks and the issuance of early warnings were also assessed. The soil lead content in the rocks of the Tieguanyin tea plantations in Anxi County followed the order: andesite > dacite > rhyolite > granite. The soil lead content gradually decreased from the center toward the east and west, forming four distinct north–south parallel zones. High-lead-content areas were identified at the border of Jiandou, Bailai, and Hushang; in the central part of Lutian; and in the southern part of Huqiu. The high levels of soil lead in the tea plantations possibly originated from industrial and mining activities, automobile exhaust, and agricultural activities. The distribution of single-factor pollution indices and potential risk evaluation based on the Soil Environmental Quality Standard, Environmental Technical Conditions for Tea Production Area, and Environmental Technical Conditions for Organic Tea Production Area indicated that the soil in Tieguanyin tea plantations in Anxi County was clean and safe for tea cultivation. [ABSTRACT FROM AUTHOR]

The effect of flume width (b) on overland flow dynamics was investigated in this study. Experiments were conducted with five different flow discharges and five flume widths (0.05–0.30 m, with an interval of 0.05 m). The findings revealed that a narrow flume had a noticeable impact on flow acceleration as the slope length increased. Relative average deviation (RAD) was calculated to evaluate the influence of sidewall effects on flow velocity. The coefficient of variation in the RAD ranged from 1.90% to 3.65%. The RAD has extremely significant differences between different widths when the flow is 0.02–0.08 m2/min. The significant differences in the RAD at different widths decrease as the flow rate increases. The flow regime was evaluated using the ratio of the thickness of the viscous sublayer to the water depth (δ/h), which proved to be a better indicator than the Reynolds number for studying flow regimes in different flume widths. Furthermore, it was observed that the energy variation was smaller in narrow flumes (b = 0.5–0.10 m) compared to wider flumes (b = 0.25–0.30 m). When the flume width ranged from 0.15 to 0.30 m, the specific energy change increased. These results contribute to further understanding of the hydraulic characteristics of overland flow and provide theoretical references for optimizing experimental design. [ABSTRACT FROM AUTHOR]

Benggang is one of the most serious soil erosion problems in tropical and subtropical areas in southern China. Little work has been reported on the surface properties of soil colloidal particle and its influence on soil swelling of different soil layers in collapsing wall of Benggang. In this present work, the effects of sodium concentration on soil swelling, and the correlations between soil swelling rates and soil colloidal surface properties were comprehensively evaluated by carefully examining soil physicochemical properties and soil colloidal surface properties of red, sandy and detritus soil layers from a collapsing wall. Our results showed that the soil swelling rates of red, sandy and detritus soil layers all exponentially decreased with increasing initial water contents. The relationship between soil swelling rate and the thickness of shear plane showed an extremely significant negative correlation for red soil layer and no correlation for sandy and detritus soil layers. Moreover, the elevating sodium concentrations reduced the thickness of shear plane from 39.69 to 0.76 nm for red soil layer, followed from 22.56 to 0.79 nm for sandy soil layer and from 18.61 to 0.64 nm for detritus soil layer. These findings indicated that the soil particle interactions played a crucial role in the development and occurrence of Benggang. This work will be helpful in understanding the mechanisms of soil mass loss on the gully head and collapsing wall of Benggang. [ABSTRACT FROM AUTHOR]

Failure of collapsing walls is an important process affecting the development of Benggang and is closely related to the soil shear strength. Plant roots can increase the soil shear strength. However, the effects and mechanisms of root reinforcement on the soil shear strength of collapsing walls remain unclear. To explore the shear strength characteristics of collapsing walls and their influencing factors under different vegetation conditions, Pennisetum sinese, Dicranopteris dichotoma, Odontosoria chinensis, and Neyraudia reynaudiana were adopted as experimental objects in the Benggang district of Anxi County, Southeast China. We measured the root characteristics and in situ shear strength of root–soil complexes by dividing soil with the four vegetation conditions into five soil layers: 0–5 cm, 5–10 cm, 10–15 cm, 15–20 cm, and 20–25 cm. The average shear strength of the root–soil complexes of the various plants ranked as follows: Pennisetum sinese (30.95 kPa) > Odontosoria chinensis (28.08 kPa) > Dicranopteris dichotoma (21.24 kPa) > Neyraudia reynaudiana (14.99 kPa) > bare soil (11.93 kPa). The enhancement effect of the root system on the soil shear strength was mainly manifested in the 0–5 cm soil surface layer. The soil shear strength attained an extremely significant positive correlation with the root length density, root surface area density, root volume density, root biomass density, for root diameters (L) less than or equal to 0.5 mm and between 0.5 and 1 mm, the soil shear strength could be simulated by using root volume density. The shear strength of undisturbed root–soil complexes measured with a 14.10 pocket vane tester was higher than the value obtained with the Wu–Waldron model (WWM). The correction coefficient k′ varied between 0.20 and 20.25, mostly exceeding 1, and the average correction coefficient k′ value was 4.94. The average correction coefficient determined in this test can be considered to modify the WWM model when conducting experiments under similar conditions. [ABSTRACT FROM AUTHOR]

'Benggang' is a local term for a widespread type of severgully erosion with steep collapsing walls in granitic, low, hilly areas of southern China, and its development and expansion are closely related to the shear strength of the collapsing wall. Plant roots play an important role in improving soil shear strength. However, the shear strength of root‐soil complexes in different layers of collapsing walls remains obscure. We selected Dicranopteris linearis fern roots and adopted the direct shear method to evaluate the effect of root weight density (RWD) (0–1.25 g 100 cm−3) on the shear properties of the lateritic, sandy and detritus layers. The results showed that roots could enhance soil shear strength, and the maximum increase in the lateritic layer was 11.53%, higher than that in the sandy (5.84%) and detritus layers (3.17%). As the root content increased, the cohesion of the sandy and detritus layers increased and then decreased, and their maximum increase in cohesion and the fitting optimal RWD were lower than those of the lateritic layer. The internal friction angle was not affected by roots. When the root content was constant, the shear strength and cohesion of the lateritic layer were significantly higher than those of the sandy and detritus layers, while their internal friction angle was significantly lower than that of the latter two layers. The average increment of soil cohesion calculated by the Wu‐Waldron model (WWM) was 10.52 kPa, which was 0.30, 3.75 and 19.38 times the measured average values of the lateritic, sandy and detritus layers, respectively. The correction coefficient k′ was 0.02–1.18, and the k'¯$$ \overline{k\hbox{'}} $$ in the lateritic layer was the highest (0.82), followed by that in the sandy and detritus layers. By combining the modified WWM with Coulomb's formula, new shear strength equations for root‐soil complexes of D. linearis were established. The predicted shear strength compared well with the measured shear strength (R2 > 0.90, NSE >0.90). Overall, the roots only had a significant reinforcement effect on the lateritic layer, and they could still not change the mechanical properties of the collapsing wall, which were more stable in the upper layers and weaker in the bottom. Therefore, other measures should be taken in the bottom layers to improve the stability of Benggangs. Highlights: Effect of D. linearis roots on the shear strength of collapsing walls in Benggang was studied.Roots could improve collapsing‐wall soil shear strength, mainly reflected in the cohesion.The roots enhancement effect in lateritic layer was better than that of sandy and detritus layers.New shear strength equations of root‐soil complexes were established based on the Wu‐Waldron model. [ABSTRACT FROM AUTHOR]

The effects of root systems on soil detachment by overland flow are closely related to vegetation types. The objective of this study was to quantify the effects of two gramineous roots (Paspalum mandiocanum with shallow roots and Pennisetum giganteum with deep roots) on soil detachment capacity, rill erodibility, and critical shear stress on alluvial fans of benggang in south‐east China. A 4‐m‐long and 0.12‐m‐wide flume was used. Slope steepness ranged from 9% to 27%, and unit flow discharge ranged from 1.39 × 10−3 to 4.19 × 10−3 m2 s−1. The mean detachment capacities of P. mandiocanum and P. giganteum lands were 18% and 38% lower than that of bare land, respectively, and the effects of root on reducing soil detachment were mainly reflected in the 0‐ to 5‐cm soil layer. The most important factors in characterizing soil detachment capacity were root length density and soil cohesion, and soil detachment capacity of the two grass lands could be estimated using flow shear stress, soil cohesion, and root length density (NSE = 0.90). With the increase in soil depth, rill erodibility increased, whereas shear stress decreased. The mean rill erodibilities of P. mandiocanum and P. giganteum lands were 81% and 61% as much as that of bare land, respectively. Additionally, rill erodibilities of the two grass lands could be estimated as an exponential function by root length density and soil cohesion (NSE = 0.88). The mean critical shear stress of P. mandiocanum and P. giganteum lands was 1.29 and 1.39 times that of bare land, respectively, and it could be estimated with a linear function by root length density (NSE = 0.76). This study demonstrated that planting of the two grasses P. mandiocanum and P. giganteum could effectively reduce soil detachment and enhance soil resistance to erosion on alluvial fans, with the deep roots of P. giganteum being more effective than the shallow roots of P. mandiocanum. The results are helpful for understanding the influencing mechanism of root systems on soil detachment process. [ABSTRACT FROM AUTHOR]

Purpose: Collapsing gully erosion is a specific form of soil erosion that is widely distributed in the hilly granitic region of tropical and subtropical southern China and resulted in extremely rapid water and soil loss. The aim of this study was to investigate the correlations between soil physicochemical and shear properties and the clay mineralogical of different profiles of the non-eroded soils (without soil erosion) and collapsing gully soils in Changting County, Fujian Province, southeastern China. Materials and methods: A total of 32 sampling soils collected from four pedons of non-eroded and collapsing gully soils were subjected to conventional soil analyses for physicochemical properties. The soil shear strength of collected soils was measured using a triaxial shear apparatus according to the unconsolidated-undrained (UU) method. The clay mineralogical of different profiles soils was examined with an X-ray diffraction (XRD) analysis. Results and discussion: The results showed that non-eroded soils had superior physicochemical characteristics. The cohesive force of the non-eroded soils was generally greater than that of collapsing gully soils. The XRD patterns of the clay fraction indicated that kaolinite, illite, hydroxy-interlayered vermiculite (HIV), and gibbsite were the dominant clay minerals in the studied soils. Pearson's correlation analysis showed that the cohesive force of the studied soils had significant and positive correlations with CEC, exchangeable Al3+ + H+, Fed, Ald, and Fet; the correlation coefficients (R value) for cohesive force were greater than those of internal friction angle. The stepwise multiple linear regression analyses indicated that exchangeable Al3+ + H+ and Ald were the dominant factors affecting cohesive force. Conclusions: Compared with collapsing gully soils, non-eroded soils had superior physicochemical and shear properties, indicating that non-eroded soils were better able to resist soil erosion. The findings obtained in the present study were of fundamental significance in understanding the correlation between shear strength and the soil physicochemical properties in the non-eroded soils and collapsing gully soils of tropical and subtropical China. [ABSTRACT FROM AUTHOR]

Core IdeasMore salts were distributed in liquid water than saline ice during the saline water freeze‐thaw process.Leaching with saline ice melt‐water was better than leaching with saline water at reducing soil EC and SAR.Gypsum application could improve the soil Ks when leached by the saline ice melt‐water.The addition of gypsum could eliminate the soil alkalinity hazards post leaching. Saline‐alkali soils adversely affect both the construction of ecological landscapes and crop production in coastal areas. This study aimed to investigate the effects of freeze‐thaw process on purifying saline water, and evaluate the potential of combining saline ice melt‐water leaching and gypsum addition for remediating coastal saline‐alkali soil. Saline water with a salinity of 10 g L−1 was tested in this study, and the leaching experiment included four treatments: saline water direct leaching (S), saline water direct leaching combined with gypsum application (SG), saline ice melt‐water leaching (SI), and saline ice melt‐water leaching combined with gypsum application (SIG). The results showed that more salts were concentrated in the bottom ice layer than in the other ice layers after the saline water was completely frozen. The salinity of the melt‐water decreased during the melting process, and the mean salinity of melt‐water during the second half of the melting process was significantly lower than the salinity of source water samples. During the leaching phase, the cumulative leachate losses of Na+, Ca2+ and Mg2+ were significantly greater for the SI treatment than that for the S treatment. After leaching, the soil electrical conductivity (EC) significantly decreased, and the SI treatment exhibited better performance than the S treatment in terms of reducing the soil EC and sodium adsorption ratio (SAR). The application of gypsum improved the soil saturated hydraulic conductivity (Ks) and decreased both the soil pH and alkalinity when the coastal saline soil was leached by the saline ice melt‐water. [ABSTRACT FROM AUTHOR]

Purpose: Collapsing gullies, which involve considerable erosion and extreme landform changes, frequently occur in the granite region of Southern China. Capturing the evolution of collapsing gullies is useful and effective for predicting erosion amount and landform changes. However, the evolution of collapsing gullies is too complex to simulate using conventional models. The aim of this study is to modify the traditional cellular automata (CA)-Markov model for simulating the evolution of collapsing gullies and then quantify their morphology using landscape pattern metrics. Materials and methods: A hillslope eroded by collapsing gullies located in Longmen Town of the granite region of Southern China is used as a case study. Three digital elevation models (DEMs) were derived on 11 March 2017, 21 July 2017, and 2 December 2017 from a remotely piloted vehicle and global positioning system (GPS) real-time kinematics. Rainfall data for the corresponding time was recorded by a tipping-bucket rain gauge. Using these data, the CA-Markov model for simulating the evolution of collapsing gullies was developed, and then the most accurate one was chosen to predict the evolution on 2 December 2018. Evolution of the case study hillslope was interpreted and assessed using landscape metrics to capture the erosional trends of collapsing gullies. Results and discussion: The area differences of the modified CA-Markov model are lower than those of the traditional model while the kappa coefficients of the modified CA-Markov model are higher than those of the traditional model; that is, the modified CA-Markov model performs better for simulating and predicting the evolution of collapsing gullies. The kappa coefficients also demonstrate that both scouring and gravity impact collapsing gullies, and scouring force is more effective than gravity. Based on the evolution prediction, the erosion amount of collapsing gullies in the subsequent year is predicted to be 904.1 m3. Spatial pattern analysis showed that the mid-lower part of a hillslope eroded by collapsing gullies will continue to be intensively eroded and the ground surface will become more fragmented. Conclusions: The use of a modified CA-Markov model and landscape pattern metrics provide an improved and effective method for understanding the spatial and temporal variations of collapsing gullies landform and ground surface, as well as better capturing the erosional trends of collapsing gullies. [ABSTRACT FROM AUTHOR]

A precise estimation of sediment transport capacity (Tc) is key to establishing process‐based erosion models. However, few data are available for estimating transport capacity on steep slopes and test materials sorted at high coarse grain values of >2 mm. Colluvial deposits with loose, coarse material and steep slopes make up the packed materials underlying the collapsing walls in benggang, which collapse due to hydraulic pressure and gravity. The objectives of this study were to investigate how flow discharge and slope steepness affect Tc and to examine relationships between Tc and flow velocity, shear stress, stream power, and unit stream power for colluvial deposits found on steep slopes. A nonerodible rill flume of 4 m long and 0.12 m wide was used. Slope steepness values ranged from 18% to 84%, and unit flow discharge values ranged from 0.56 × 10−3 to 4.44 × 10−3 m2 s−1. Tc increased as a power function with flow discharge and slope steepness with a Nash–Sutcliffe model efficiency (NSE) value of 0.99, and the effects of flow discharge were stronger than those of slope steepness. Tc was overestimated for a colluvial deposit when the equations of the ANSWERS, Zhang et al. and Wu et al. models were considered and when Tc exceeded 5 kg m−1 s−1, as the slope steepness used in our study was much higher than those used (<47%) in the other models. Regression analyses show that Tc can be predicted from linear equations of flow velocity, stream power, and unit stream power, and Tc can be fit to shear stress with power function equation. Flow velocity optimizes to predict Tc with NSE = 0.97, and stream power and shear stress can also be successfully related to Tc (NSE = 0.91 and NSE = 0.81, respectively); however, unit stream power performs poorly (NSE = 0.67). These results provide a basis for establishing process‐based erosion models on steep colluvial slopes. [ABSTRACT FROM AUTHOR]

The paper used the unmanned aerial vehicle (UAV) which can quickly obtain a wide range of vegetation images to capture the low-altitude aerial photograph)' and associated with the multivariate HoG features to recognize vegetation types. Firstly, the texture infonnation of the image were extracted by Gabor filter and using HSV and Lab color space transform to extract the color infonnation. Next, the image were divided into N cells, then computing the gradient of histogram of each cell based on the texture and color infonnation to fonn the multivariate HoG features. Finally, taking the cell as the classification unit, combining the random forest machine learning algorithm, vegetation types recognition model were established. Taking the Anxi County in Fujian Province as the test area, the results showed that it was feasible to identify the vegetation types by using the optical image of low-altitude aerial photography; the highest recognition accuracy in recognizing vegetation and non-vegetation was 96.04%; the recognition accuracy rate was 82.44% in recognizing vegetation types at 20 m and decreased with the height increase. Moreover, the vegetation images of aerial photography were further collected, which was captured at the Changting County of Fujian Province, as another data to prove the robustness of the model of vegetation type recognition in different areas, the highest recognition accuracy was 73.31%, the accuracy was similar compared with the result of Anxi County. In this paper, the vegetation images by using the unmanned aerial vehicle with optical camera were conveniently, econmically obtained; the proposed vegetation type recognition model can be easily applied to the field vegetation type monitoring and management as the high precision and its robustness in various regions. In addition, according to the recognition result at various aerial height, the proposed aerial height should not be too high, 20 m as the reference height of aerial photography was suitable. [ABSTRACT FROM AUTHOR]

A method has been found for the regioselective alkylation of the nitrogen at the 1-position of 2′-deoxyguanosine. This consists in the reaction, in tetrahydrofuran solution, of a fully protected form of dG, namely the 3′5′-O-bis(tert-butyldimethylsilyl)-N2-dimethylaminomethylene derivative, with an alkyl halide in the presence of cesium carbonate. The yields of these previously unavailable derivatives of 2′-deoxyguanosine range from good to excellent. Confirmation of the structure of these substances comes from a comparison of their spectroscopic properties with those of the known 1-methyl homologue. In particular, the UV spectra of these new derivatives and the known 1-methyl homologue are essentially identical. [ABSTRACT FROM AUTHOR]

Except for the catalyst and the temperature, the nature of the solvent also affects the aldol condensation, favouring α,β-unsaturated carbonyl compounds in alcoholic solvents or β-hydroxyl carbonyl compounds in tetrahydrofuran. [ABSTRACT FROM AUTHOR]