Objective This study aims to investigate the effects of different vegetation restoration models on runoff and sediment reduction in dry-hot valleys and to analyze their underlying mechanisms， thereby providing a scientific basis for functional vegetation restoration for soil and water conservation in these areas. Methods Taking the Yuanmou dry-hot valley in Yunnan Province as the study area， an in-situ monitoring experiment was conducted from 2019 to 2022. Bare land was used as the control， and vegetation restoration models including cultivated land， shrub-grassland， tree-shrub-grassland， naturally restored land 1 and naturally restored land 2 were established. The runoff and sediment reduction benefits under different vegetation restoration models were compared， and the influence mechanisms of rainfall， soil， and vegetation factors on soil loss and runoff under different models were explored. Results Compared with bare land， runoff decreased by 64.25%， 89.08%， 91.81%， 87.20% and 84.79%， and soil loss decreased by 92.16%， 99.45%， 99.92%， 99.37% and 97.26% in cultivated land， shrub-grassland， tree-shrub-grassland， naturally restored land 1， and naturally restored land 2， respectively. The effectiveness of runoff and sediment reduction followed the order： tree-shrub-grassland > shrub-grassland > naturally restored land 1 > naturally restored land 2 > cultivated land > bare land. Rainfall erosivity was the major driving factor of runoff， with a total effect ranging from 21.90% to 70.73%， while runoff was the primary driving factor of soil loss， with a total effect ranging from 26.94% to 97.81%. In bare land and intensively disturbed cultivated land， the water and sediment processes were mainly dominated by rainfall factors （rainfall erosivity）. In contrast， under restoration models such as shrub-grassland and tree-shrub-grassland， the system shifted to being dominated by "surface hydrological processes"， where vegetation and soil factors fundamentally reduced the occurrence of runoff and soil loss by curbing runoff volume. Conclusion The tree-shrub-grass model combining Bombax ceiba， Bauhinia purpurea， Heteropogon contortus， and Bothriochloa pertusa was the most effective in reducing runoff and sediment. This model achieves significant soil and water conservation benefits by jointly regulating soil and vegetation factors to suppress the generation of runoff and soil loss.

Objective This study aims to investigate the spatiotemporal evolution characteristics and driving factors of soil conservation in the Three Gorges Reservoir area. Methods Taking Wanzhou， a representative county in the Three Gorges Reservoir area， as a case study， multi-source remote sensing data from 1990 to 2020 were used. The InVEST model was applied to assess the spatial differentiation characteristics of soil conservation function， and the Geodetector model was employed to analyze the driving mechanisms of its evolution. The influence of slope on soil conservation in sloping cropland and corresponding regulation measures were also explored. Results 1） From 1990 to 2020， soil conservation function in Wanzhou exhibited a trend of increase followed by decrease， with a spatial pattern of higher values in the east and lower values in the west. Land use types were mainly sloping cropland and forest land. 2） Soil conservation function in Wanzhou demonstrated significant spatial clustering characteristics， with low-low clustering areas expanding from the north to the southwest， and high-high clustering areas concentrated in the eastern region. Kernel density high-value areas were consistently located in the central region， and kernel density values showed a fluctuating decrease followed by an increase. 3） Natural environmental factors were the primary drivers of spatial differentiation in soil conservation function. Slope （q=0.71） was the dominant factor， followed by vegetation coverage （q=0.43） and soil type （q=0.24）. Interactions among all factors showed enhancement effects， among which combinations such as slope and temperature， and slope and vegetation coverage， exhibited the strongest effects （q>0.75）. 4） Soil conservation function in sloping cropland was closely related to slope. On slopes from 3° to 8°， soil conservation function remained stable ［from 120.64 t/（hm²·a） to 379.35 t/（hm²·a）］. On slopes from 8° to 25°， it was at a moderate level ［from 61.17 t/（hm²·a） to 81.93 t/（hm²·a）］. Differentiated management measures could be adopted for different slope gradients： low-slope areas should adopt straw mulching and contour ridge tillage， medium-slope areas should combine engineering and vegetation measures， and slopes >25° should prioritize conversion of cropland to forest and grassland. Conclusion The results provide a scientific basis for soil erosion control and ecological restoration in the Three Gorges Reservoir area.

Objective This study aims to clarify the spatiotemporal evolution patterns， obstacle factors， and cultivated land improvement zoning in the Loess Plateau of northern Shaanxi from 1990 to 2020， and to optimize the regional allocation of cultivated land resources and achieve the strategy of "grain security in the land". Methods Taking Yulin City as the study area， the evaluation indicator system for cultivated land quality mainly covered five aspects： climatic conditions， soil nutrients， cultivated land management， site conditions， and physicochemical properties. The spatial autocorrelation model and the obstacle degree model were introduced to analyze the spatiotemporal evolution characteristics and core restrictive factors of cultivated land quality， and based on this， the improvement zones were scientifically delineated. Results 1） From 1990 to 2020， the cultivated land quality index in Yulin City showed an upward trend （rising from 0.52 to 0.55）， with a spatial distribution pattern of "higher in the east and lower in the west， and higher in the south and lower in the north". 2） The spatial heterogeneity was significant. The high-high-clustering-type cultivated land was distributed in Suide County， Wubu County， and other loess hilly-gully regions， while low-low-clustering-type cultivated land was concentrated in Dingbian County， Jingbian County， and other sandy grassland areas. 3） The diagnosis of obstacle factors indicated that accumulated temperature was the primary factor restricting cultivated land quality in Yulin City. Based on the dominant obstacle factor types， the city was divided into 22 regional types， including accumulated temperature zone， average patch area-pH zone， and organic carbon zone， with differentiated improvement plans proposed for key zones. Conclusion The research findings can provide a scientific basis for cultivated land quality protection and high-quality agricultural development in the northern Shaanxi Loess Plateau.

Objective This study aims to determine the optimal irrigation timing under the single-irrigation mode during the growth period for winter wheat in Hebei Province. Methods Using winter wheat cultivar Jimai 22 as the test material， a field experiment was conducted over two growing seasons （2021-2022 and 2022-2023）. Three irrigation and nitrogen topdressing timing treatments were implemented： at the 4th （T4）， 5th （T5）， and 6th （T6） leaf visible stages in spring. The effects of irrigation and nitrogen topdressing at different timings on wheat water consumption characteristics， dry matter accumulation， grain yield， and its components were analyzed. Results Under the condition of single-irrigation mode during the growth period， the proportion of water consumption sources and the stage-specific distribution of water consumption in wheat were significantly influenced by the climatic year type. Delaying irrigation had no significant effect on soil water storage consumption or total water consumption throughout the entire growth period and during each stage before and after anthesis， and only promoted the utilization of deep soil water in the 2022-2023 growing season with more precipitation. Pre-sowing soil water storage and water use efficiency showed significant positive correlations with grain yield， while total water consumption showed no significant correlation. Therefore， ensuring water supply at critical stages was more important. Spike number was significantly positively correlated with yield， and grain weight per spike was significantly negatively correlated with yield. Delaying irrigation decreased spike number but increased grain weight per spike. The T6 treatment yielded the lowest during both growing seasons， and the fundamental reason for the yield reduction was that the decrease in spike number exceeded the increase in grain weight per spike. In the 2021—2022 growing season with a pre-sowing soil water storage of 655.74 mm， the T5 treatment showed a slight decrease in spike number and achieved the highest yield. In the 2022-2023 growing season with a pre-sowing soil water storage of only 541.24 mm， the T5 treatment showed a larger decrease in spike number， and the T4 treatment achieved the highest yield. Conclusion Under the single-irrigation mode during the growth period for wheat， prioritizing a higher spike number is key to achieving high yield. When pre-sowing soil water storage is greater than 600 mm or spring rainfall is sufficient， the irrigation can be postponed to the 5th leaf visible stage in spring to balance the grain weight. When pre-sowing soil water storage is less than 550 mm or in drought years， the irrigation must be conducted at the 4th leaf visible stage in spring to ensure spike number. The research findings can provide a theoretical basis and technical support for the water-limited and high-yield cultivation of winter wheat in Hebei Province.

Objective This study investigates the response characteristics of water storage at gully heads to rainfall in the black soil region of Northeast China， reveals the variation patterns of water storage at gully heads before and after rainfall， and establishes a quantitative prediction method for its changes before and after rainfall. Methods Four gully heads with similar developmental stages and scales in three study areas （Jiusan， Binxian and Jiutai） were selected as research objects. Differences in soil hydraulic parameters， decay coefficients of water storage， and variation patterns of water storage before and after rainfall were investigated through transient water release and imbibition method （TRIM）， numerical fitting， and prediction model construction. Results Obvious hysteresis effects were observed in soil-water characteristic curves （SWCC） of soils at gully heads， with the intensity ranking as gully 1 ≈ gully 2 < gully 3 < gully 4. After rainfall， water storage decayed exponentially over time， showing rapid decline in the initial stage and slower decline in the later stage. The decay coefficient （K_d） of water storage decreased progressively with increasing soil depth. Model simulations showed that water storage changes at 85.7 % of the monitoring sites were best predicted using 1 h maximum rainfall intensity （I_{1 h}） as the rainfall input parameter， whereas 14.3 % of the sites were better simulated using 2 h average maximum continuous rainfall intensity （I_{2 h}） as input. Therefore， in predicting soil water storage changes， I_{1 h} could be selected as the rainfall input parameter for sites with good infiltration performance， such as gully heads or severely eroded sites. However， I_{2 h} should be selected as the rainfall input parameter for sites with poor infiltration performance or strong water redistribution. Conclusion The evolution of water storage at gully heads after rainfall in the black soil region of Northeast China can be effectively characterized using exponential decay patterns and short-duration rainfall indices. The constructed model can accurately and quantitatively predict short-duration water storage changes at gully heads at the event scale， which provides methodological support for prediction and early warning of gully erosion processes.

Objective To clarify the zonal characteristics of litter water-holding capacity in Robinia pseudoacacia forests and their response mechanisms to mixing patterns on the Loess Plateau. Methods Taking R. pseudoacacia forests on the Loess Plateau as the research subject， the litter was collected from a total of 31 sample plots of pure R. pseudoacacia forests （R_p） and mixed R. pseudoacacia forests ［R. pseudoacacia×Platycladus orientalis （R_p×P_o）， R. pseudoacacia×Prunus sibirica （R_p×P_s）， R. pseudoacacia×Pinus tabuliformis （R_p×P_t）］ in the forest zone， forest-steppe zone and steppe zone to study litter water-holding capacity. Results 1） In all three vegetation zones， the maximum water-holding rate of litter in pure R. pseudoacacia forests （R_p） was higher than that in mixed R. pseudoacacia forests. In the steppe zone， R_p was 5.1% higher than R_p×P_t. In the forest-steppe zone， R_p was 5.6%， 5.3%， and 11.4% higher than R_p×P_o， R_p×P_s， and R_p×P_t， respectively. In the forest zone， R_p was 11.6%， 11.5%， and 20.3% higher than R_p×P_o， R_p×P_s， and R_p×P_t， respectively. Among these， R_p was the lowest in the steppe zone （147.88%）， while the values in the forest-steppe zone （180.80%） and forest zone （170.31%） were relatively similar and higher. For R_p×P_t， the value was the highest in the forest-steppe zone （162.28%）， while the values in the steppe zone （140.64%） and forest zone （141.60%） were similar and lower. 2） During the water absorption-evaporation process， the water-holding rate varied with time： it increased logarithmically during the absorption stage and decreased exponentially during the evaporation stage， with both change rates following a power function decay. 3） The effective water interception capacity of R_p and R_p×P_t was positively correlated with mean annual precipitation and mean annual temperature， and the capacity in the steppe zone was abruptly lower than that in the forest-steppe zone and forest zone. Regarding the optimal forest type within each vegetation zone， R_p in the steppe zone （7.17 t/hm²） was the highest， followed by R_p×P_o in the forest-steppe zone （16.27 t/hm²） and R_p×P_t in the forest zone （17.45 t/hm²）. 4） Partial Least Squares Structural Equation Modeling （PLS-SEM） revealed that climate and topography first directly affected vegetation， and then together with vegetation jointly influenced litter water-holding capacity. Topography could also directly affect the water-holding rate. Conclusion The effective interception capacity of litter in R. pseudoacacia forests on the Loess Plateau is positively correlated with precipitation and temperature. The optimal forest types for the steppe， forest-steppe， and forest zones are R_p， R_p×P_o， and R_p×P_t， respectively. The results provide a theoretical basis for optimizing water conservation forests and assessing regional functions.

Objective This study reveals controlling mechanisms and relative importance of interface roughness， particle gradation， and coupling effects of temperature and thickness on the development of soil desiccation cracking， providing a theoretical basis for preventing engineering hazards such as anti-seepage failure and mechanical instability of soil masses. Methods Sediments from Qingshitan Reservoir in Guilin were selected as test materials， and a series of laboratory drying model tests were designed and conducted covering different particle gradations （intrinsic components）， bottom interface roughness （boundary conditions）， and drying temperatures and initial soil layer thicknesses （environmental and geometric conditions）. High-precision imaging equipment was used to record the whole process of water evaporation and crack evolution in soils. Digital image processing techniques were applied to perform binarization and skeletonization of crack networks to quantitatively extract characteristic parameters such as crack ratio， average crack width， and fractal dimension. Range analysis was employed to systematically calculate and compare the contribution weights of different factors to desiccation cracking development. Results 1） Interface roughness was the primary controlling factor of crack network development and morphological evolution， with a contribution weight of 57.08% to crack ratio. Increased interface roughness significantly enhanced geometric complexity and topological connectivity of crack networks and induced significant curling at soil edges. 2） Particle gradation， acting as an intrinsic factor， had a contribution weight of 26.98%. An increase in fine particle content showed significant positive correlations with crack ratio， crack width， and fractal dimension， fundamentally determining volumetric shrinkage potential and final cracking modes of soils. 3） The combined contribution rate of temperature and thickness was approximately 16.00%. Specifically， the contribution weight of initial layer thickness （9.18%） was significantly higher than that of the drying temperature （6.76%）. The former dominated macroscopic distribution patterns of cracks primarily by constraining the release range of tensile stress， while the latter exhibited relatively complex non-monotonic variation characteristics. Conclusion The dominant factors controlling soil desiccation cracking development are interface roughness and particle gradation， while environmental temperature and initial thickness play secondary synergistic roles. The results provide a scientific basis for the prevention and control of cracking hazards， material improvement， and construction process optimization of anti-seepage soil masses in practical geotechnical engineering.

Objective This study aims to investigate the response status， regional differences， and influencing factors of habitat quality and landscape patterns in the Huaihe River basin and the Haihe River basin， providing theoretical support and a scientific basis for decision-making in the development of differentiated ecological protection strategies for the river basins. Methods Land use data from five periods between 2003 and 2023 were selected. The InVEST model was used to evaluate habitat quality in the river basins， and landscape pattern indices were calculated. The bivariate spatial autocorrelation method was employed to analyze the response relationship and inter-basin differences between the two. Furthermore， the explanatory power of physical geographical factors on the spatial differentiation of habitat quality was explored. Results 1） Cultivated land area decreased significantly in the Huaihe River basin （-20 394.68 km²） and the Haihe River basin （-13 783.16 km²）， while the areas of forest land， water bodies， and construction land all increased. Habitat quality was predominantly at low levels and declined over time， with decreases of 6.48% and 6.55%， respectively. 2） Habitat fragmentation gradually intensified in both river basins， while patch shape complexity remained stable （FRAC_MN fluctuation < 0.003）. Habitat quality in the Huaihe River basin showed a positive correlation with contagion （CONTAG） and prominent negative responses to patch shape complexity and land distribution uniformity. In contrast， habitat quality in the Haihe River basin was mainly negatively affected by the intensification of fragmentation. 3） Topographic factors were the core driving factors of habitat quality changes in the Huaihe River basin （q = 0.295） and the Haihe River basin （q = 0.467）， followed by atmospheric pollution stress （PM_2.5， O₃）， exhibiting spatiotemporal dynamics. The explanatory power of the interactions among natural environmental factors was stronger than that of single factors. Conclusion The evolution of habitat quality in the Huaihe River basin and the Haihe River basin exhibits differentiated characteristics. The heterogeneity of the response mechanisms between habitat quality and landscape patterns in the river basins requires the implementation of zonal governance and targeted restoration strategies to enhance the stability and service functions of regional ecosystems.

Objective This study aims to quantify the spatiotemporal evolution of ecosystem service functions in the Horqin sandy land， providing a scientific basis and theoretical support for environmental management and ecological restoration. Methods Based on land use data from three recent periods （2000， 2010， and 2020）， the InVEST model was used to quantitatively evaluate five key ecosystem service indicators in the Horqin sandy land， including annual water yield， water quality purification （phosphorus load）， soil conservation， carbon storage， and habitat quality. The ecosystem service index was calculated. Results 1） Ecological land （grassland and forest land） and construction land increased over the periods， while cultivated land， unused land， and water areas decreased continuously. 2） Annual water yield increased over the periods， with the mean value rising from 131.19 mm to 266.39 mm. Highvalue areas （300.00~400.00 mm） in the western region expanded significantly， and the spatial distribution across the region shifted from lowvalue dominance to concentration in highgradient zones （>200.00 mm）. 3） The overall water purification capacity showed a declining trend， with the average value decreasing from 1.31 kg/km² to 1.22 kg/km². Highvalue areas in the eastern region contracted generally，accompanied by weakened spatial heterogeneity. 4） Soil conservation and carbon storage were influenced by vegetation distribution and elevation， showing a pattern of high values at high elevations and low values at low elevations. The mean soil conservation increased from 27.72 t/km² to 60.38 t/km²， while the mean value of carbon storage remained stable from 143.41 t/km² to 144.86 t/km². Highvalue areas （≥80.00 t/km²） continued to expand. 5） Habitat quality improved over the periods， with the mean value increasing from 0.28 to 0.30， while spatial heterogeneity remained stable. 6） The ecosystem service index increased with the expansion of ecological land， while fragmentation in lowvalue areas （<0.20） intensified. Conclusion Expansion of forest-grassland has significantly improved ecosystem service functions in the Horqin sandy land， increasing annual water yield and reducing phosphorus load， while promoting coordinated enhancement of soil conservation and carbon storage. This provides a scientific basis for achieving ecological restoration in the arid and semi-arid regions of northern China.

Objective This study aims to investigate the interactive effects of plastic film mulching and combined soil amendments on the soil quality index （SQI） and maize yield， in order to achieve the synergistic improvement of soil quality and maize yield in the dryland farming systems of Northwest China. Methods A three-factor randomized block design was adopted， including two mulching methods： no mulching （M0） and black plastic film mulching （M1）， two application rates of water-retaining agent （W0： 0 kg/hm²； W1： 45 kg/hm²）， and three application rates of biochar （B0： 0 t/hm²； B15： 15 t/hm²； B30： 30 t/hm²）. The effects of different treatment combinations on soil physicochemical properties， SQI， and maize yield were compared. Results 1） Both mulching and amendments improved soil physical structure. The W1B30 treatment reduced the bulk density in the 0-40 cm soil layer by an average of 4.29% and increased porosity， field water capacity， and saturated water content. Mulching provided a more stable hydrothermal background for the amendments to function， resulting in more pronounced improvements in surface structure and water-holding capacity. 2） The improvement in soil chemical properties was mainly attributed to biochar. In the 0-20 cm soil layer， soil organic carbon （SOC） in the W1B30 treatment increased by 23.73% compared to the control， while available phosphorus and available potassium increased by 22.66% and 9.86%， respectively. The extent of improvement in SOC and nutrient availability by amendments differed under different mulching conditions， indicating that mulching methods regulated the response of C and N accumulation and available nutrients to amendments. 3） The combined application of plastic film mulching and amendments jointly promoted maize yield， and the yield was more sensitive to mulching×amendment interactions. Under the no mulching condition， W1B30 increased yield by 19.25%， while with mulching， W1B15 increased yield by 18.61%. SQI showed a significant positive correlation with yield （R² =0.67）， and the SQI of the W1B30 treatment increased by 138.95%. Conclusion Plastic film mulching significantly increases maize yield. The combined application of amendments markedly improves the physical structure of dryland farmland soil， enhances water and nutrient retention， thereby increasing soil fertility and achieving synchronous improvement of soil quality and yield. This study provides a basis for optimizing mulching management and amendment application in dryland regions， and for advancing sustainable production with reduced or no plastic film.