Abstract:Aiming at the complex characteristics of rheological properties and dynamic process of debris flow, on the basis of systematically collecting relevant literatures on numerical simulation of debris flow in China, the history and current situation of numerical simulation of debris flow in China are summarized according to three stages:preliminary exploration, gradual improvement and maturity. According to the material composition and dynamic characteristics, the dynamic model of debris flow can be divided into continuous medium, discrete medium and mixed medium model. By analyzing the characteristics and application scenarios of different models, the applicability and shortcomings of various models and numerical calculation methods are compared and summarized. On this basis, in view of some difficulties in the debris flow simulation, the future development of debris flow numerical simulation is prospected, aiming to providing reference for debris flow numerical simulation research and application software development.

Abstract:With the development of molecular biology, the role of soil microorganisms has changed the scientific understanding of formation and sequestration of soil organic carbon (SOC). Microbial residue combined with soil minerals to form mineral-associated organic carbon (MAOC), which has improved our understanding of soil organic carbon sequestration. MAOC is a fraction of soil organic carbon dominated by soil microbial residue carbon. It is mainly composed of identifiable microbial residue with low molecular weight bound to the mineral surface. As MAOC contributes more than 50% to soil organic carbon pool of grassland and agricultural ecosystems and has a long turnover time (centennial-millennial scale), the study of MAOC formation process and stabilization mechanism has become the focus of soil carbon sink in the context of carbon neutrality. Recent studies clearly indicate that the formation and stability of MAOC are not only mainly related to microbial residue carbon, but also closely associated with soil minerals. Based on this, we focus on the cutting-edge scientific issue of microbial carbon pump regulating soil organic carbon and provide an overview of the scientific framework on soil microbial residue contribution to MAOC. The aim is to reveal the contribution of LMW-DC (low molecular weight dissolved carbon substrate) from different sources to MAOC formation, and to explore the mechanism of selective adsorption of LMW-DC by soil minerals. Meanwhile, the relevant factors affecting the contribution of MAOC to stabilizing carbon pools are also discussed. It also provides an outlook on the future development of this research field, with a view to exploring the differences in the regulation of soil microorganisms in different ecosystems, soil types and soil depths from the molecular level, so as to provide a theoretical reference for the research on soil organic carbon sequestration and a scientific evidence for enriching soil carbon source/sink functions.

Abstract:Soil crust has an important influence on water infiltration and erosion sediment production on slope, but its specific process and mechanism are still under debate. In this study, taking the alien soil slope in mining wasteland of Wula Mountain as the research object, the effects of soil crust on runoff and sediment were investigated by in situ scouring tests on the slopes with different slope lengths (2 m, 4 m, 6 m, 8 m and 10 m) and during flow and sand production process.The results showed that:(1) The total runoff and sediment yield on the 2 m slope increased significantly, which were 2.17 and 1.56 times of that on the control slope. The total runoff and sediment yield on the 4 to 10 m slopes decreased, and the total runoff was 67.17% to 78.45% of that on the control slope and the total sediment yield was 54.53% to 83.56% of that on the control slope. (2) The changes of runoff rate with time on the soil crust slope and the control slope were basically the same, showing a fluctuating and stable or slightly increasing trend. The sediment yield rate on the control slope showed a decreasing trend with time, while on the soil crust slope showed two trends of decreasing and stabilizing. (3) The relationship between cumulative runoff, cumulative sediment yield and runoff generation time could be expressed by linear function and power function. With the change of runoff generation time, the effects of soil crust slope on the accumulated runoff volume could be divided into three types:increase, decrease, increase firstly and then decrease. And the effects on the accumulated sediment yield could be divided into two types:increase and decrease. Therefore, the inhibiting or promoting effect of soil crust on process of runoff and sediment yield on the slope surface was closely related to the slope length and erosion occurrence process.

Abstract:The soil and water loss caused by the construction service road in engineering construction is different from the traditional soil erosion. The construction service road changes the original natural slope morphology and hydrological process, resulting in vegetation destruction, surface exposure, and has formed road surface, excavating and filling slope and other erosion and sand production sites. The road cut and slope of side with loose structure have stronger and faster response to rainfall. Soil erosion caused by soil low grade roads accounts for a large proportion, so the study provides a basis for the prevention and control of soil erosion in the construction of roadways. Taking Bayi District, Nyingchi City, as the research object, using WEPP model to simulate and analyze the runoff and soil loss of under different precipitation conditions, different slope and slope length under engineering disturbance, so as to reveal the characteristics and key influencing factors of water and soil loss. The results showed that:(1) When the maximum rain intensity in 60 min (I₆₀) was 11.16 mm/h and the rainfall was 12.40 mm, runoff began to occur; When I₆₀ was in the range of 10 to 17 mm/h, the runoff was less than 0.50 mm, and the soil loss was less than 0.010 kg/m². When I₆₀ was more than 17 mm/h, I₆₀ had a linear relationship with the runoff and soil loss. (2) The runoff presented three stages of "rapid increase-slow down-gradual decrease" with the increase of slope. The lowest runoff was 56.98 to 58.00 mm when the slope was 5°, and the highest runoff was 76.19 to 77.01 mm when the slope was 30° to 35°. Soil loss presented two stages of "first rapid increase and then stable" with the increase of slope. When the slope was below 5°, the amount of soil and water loss was small, and the slope became stable after 50°. (3) With the increase of slope length, the runoff of backer slope decreases, while the runoff of non-backer slope remains stable. The runoff of backer slope was lower than that of non-backer slope after 50 m slope length, and the difference increases with the increase of slope length; With the increase of slope length, the soil loss of the backer slope showed a trend of "first rapid increase and then decrease", and the soil loss of the non-backer slope basically kept a uniform increase. The results can be used to analyze the driving mechanism of soil and water loss in slope after engineering disturbance in high and cold region.

Abstract:The sediment concentration of runoff reflects the fluctuation and evolution of the runoff-sediment relationship, and can be used as an important index to evaluate the characteristics of the interactive evolution process of runoff and sediment yield under the influence of vegetation. The influence of different grass covers on sediment concentration of runoff on loess slope under different rainfall intensities and slopes were studied through artificial rainfall experiment. The results showed that:(1) The greater the grass cover, the more delayed the initial time of slope runoff production. The sediment concentration of runoff on slopes covered with grass fluctuated in the beginning 15 min of rainfall, but showed a decreasing trend on the whole, and then reached a stable state, and the sediment concentration of runoff on the slope covered with grass was significantly lower than that on the bare land. (2) The average sediment concentration of runoff increased with the increasing of both rainfall intensity and slope, and the responses of average sediment concentration to both rainfall intensity and slope could be described by power function equations, with R² ranging from 0.823 to 0.974 and 0.880 to 0.971, respectively. The average sediment concentration decreased with the increasing of coverage, and the influence of rainfall intensity on the average sediment concentration weakened with the increasing of coverage. The response of average sediment concentration to coverage could be described by linear equation with R² ranging from 0.732 to 0.979. (3) The response of average sediment concentration to coverage and rainfall intensity (R²=0.822, NE=0.921, p<0.01), coverage and slope (R²=0.975, NE=0.697, p<0.01) could be described by binary power function equation. And the comprehensive response of average sediment concentration to coverage, rainfall intensity and slope could be described by a ternary linear equation (R²=0.771, NE=0.774, p<0.01). Among them, the model based on coverage and rain intensity and the model based on coverage, rain intensity and slope had the best fitting effect. The degree of influence on sediment concentration followed the order of coverage>rain intensity>slope. The results could provide references for the research of change characteristics and mechanisms of sediment concentration on loess slope, and have important significance for soil and water loss control and sustainable development of ecosystem on the Loess Plateau.

Abstract:Large number of production and construction projects disturb the surface and destroy the original surface vegetation with the rapid development of economy and society and the rapid increase of engineering construction projects. Large-scale and unbalanced excavation and filling make excess soil and rock mixed and accumulated. The excess soil-rock mixed media formed in the construction of mountain projects are accumulated in the upstream and slope of ditches and rivers, which is prone to serious soil and water loss under heavy rainfall conditions, and even cause disasters such as landslides and debris flows. This study took the artificially remolded spoil heaps (with a slope degree of 25°) as the research object, and carried out the research on the influence of slope length (3 m, 5 m, 6.5 m, 12 m) and gravel content (0, 10%, 20%, 30%) on the spatial distribution characteristics of velocity and sediment yield characteristics of spoil heaps under extreme rainfall conditions (with a rainfall intensity of 2.5 mm/min) through the simulated rainfall test. Results showed:(1) The flow velocity was in a fluctuating state during the whole rainfall process, and the fluctuation amplitude decreased with the increase of gravel content and mass fraction under slope length by 12 m. However, the flow velocity under the slope length of 3 m, 5 m and 6.5 m increased at first and then tends to be stable with the runoff duration. The average velocity of the middle and lower slope was 1.12 to 1.54 times that of the middle and upper slope. With the increased of the slope length, the average velocity of the flow increased by 17.81% to 335.94%, and the average velocity of spoil heaps with gravel was 22.88% to 54.67% lower than that of the pure spoil heaps. The mass fraction of gravel had more significant effect on the flow velocity than the slope length. (2) The average soil loss rate of pure spoil heaps increased significantly with the slope length, with an increment of 7.88% to 87.67%. However, the gravel-bearing spoil heaps decreased with the increasing of slope length from 3 to 5 m (decreased by 9.10% to 28.86%), but then increased significantly. There is a critical slope length. The average soil loss rate of spoil heaps with slope length of 6.5 m and 12 m is 22.33% to 122.48% higher than that of slope length of 3 m. Gravel could significantly reduce the slope erosion of spoil heaps, and its sediment reduction efficiency reached 24.99% to 59.54%. The contribution rate of gravel to the average soil loss rate of spoil heaps was 1.13 times of the slope length. (3) The impact of flow velocity on the soil loss rate in the upper and middle slope of the spoil heaps was greater than that in the lower and middle slope. There was a significant correlation between the average soil loss rate and flow velocity. The flow velocity could be used as a characteristic parameter of the average soil loss rate, and its linear fitting relationship (R² was 0.67 to 0.95). The results further deepen the connotation of soil erosion discipline, which can provide data basis for the prediction model of spoil heaps erosion of construction production and construction projects, and also provide theoretical basis for clarifying the internal mechanism of engineering disturbance slope erosion.

Abstract:A large number of epi-karst zones have developed on karst slopes, with strong infiltration, and the runoff production mechanism is very different from that of non-karst slopes. In order to improve the prediction accuracy of soil erosion models in karst areas, six runoff plots of different land-use types in the Chenqi Small Watershed of Puding County, Guizhou Province, were taken as the observation objects. The sediment and surface runoff data under different vegetation cover from two periods of 2007-2010 and 2015-2019 were analyzed to understand the laws of runoff and sediment production, and the erosive rainfall of each plot was calculated by using the rainfall erosion force deviation method. The results showed that:(1) Vegetation coverage was negatively correlated with runoff and sediment production on karst slopes. Under high vegetation coverage, heavy rains and extreme heavy rains were the main rainfall types that cause soil erosion on karst slopes. (2) Over the past decade of vegetation restoration, with the improvement of coverage, the annual average soil loss showed a downward trend, mostly less than 10 t/km². (3) The karst slope developed fissures, serious underground leakage, small amount of soil and was not easy to be eroded. Except for a few extreme heavy rainstorm, most rainfall did not produce runoff and sediment. Therefore, it is recommended to set the threshold of erosive rainfall on karst slopes at 50 mm, which is generally significantly higher than that in non-karst areas.

Abstract:Biological soil crusts (biocrusts), which develop commonly in the southwestern karst regions, have a significant effect on reducing soil erosion. To explore the effect of biocrusts on soil anti-erodibility, biocrusts with different rehabilitation ages (0, 3, 5, 8, 11 a) were studied on a karst hillslope in Guizhou, and different levels of flow discharge (0.2, 0.3, 0.4, 0.5 L/s) and slope gradients (5°, 12°, 17°, 23°) were designed. The results showed that:(1) Biocrusts on karst hillslopes could promote soil particles cementation, strengthen soil aggregate stability, improve soil structure, and enhance soil water holding capacity and permeability. (2) The biocrusts greatly enhanced the anti-disintegration and anti-shear strength of soil. Compared with the treatment of removing biocrusts, the soil's anti-disintegration and anti-shear strength of the treatment of retained biocrusts increased by 24.83%~46.62% and 25.77%~37.73%, respectively. (3) The tensile strength of the biocrust layer ranged from 1.95 to 5.76 N during the rehabilitation ages (3~11 a). As the development age of biocrusts increased, the structure of the biocrust layer became more stable, and its ability to resist damage became stronger. (4) The biocrusts could also significantly improve the soil anti-scour capacity, which was regulated by flow discharge and slope gradient. The critical value for flow discharge and slope gradient was 0.4 L/s and 17°, respectively, beyond which the protective effect of biocrusts was significantly weakened. These results were of great significance for accurately estimating soil erosion and correctly evaluating ecological restoration construction in karst regions.

Abstract:In order to explore the influence of biocrust with different coverage on infiltration process, biocrust from quaternary clay developed red soil (S type) and argillaceous shale developed soil (N type) were selected in the red soil hilly area of Xianning. And six coverage levels (bare land, 1%~20%, 20%~40%, 40%~60%, 60%~80% and 80%~100%) were set. The Mini disk infiltration instrument was used to determine the soil infiltration process and explore the factors affected the infiltration process, meanwhile three common models were used to simulate the infiltration process and the suitability of the model were compared. The results showed that:(1) Compared with bare soil, the development of two types of biocrust increased soil organic carbon, clay content, crust thickness and biomass, while decreased sand content. (2) The water infiltration characteristics of S-type soil decreased gradually with the increasing of biocrust coverage. The initial infiltration rate, stable infiltration rate, average infiltration rate and unsaturated water conductivity varied from 0.25 to 1.55, 0.13 to 0.91, 0.17 to 1.11 and 2.04 to 8.48 mm/min, respectively. In N-type soil, the soil water infiltration decreased with the increasing of coverage except for 40% to 60% (high gravel content). The initial infiltration rate, average infiltration rate and stable infiltration rate of 80% to 100% coverage decreased by 91.14%, 87.64% and 91.30%, respectively, compared with the bare soil. The presence of biocrust impeded the soil water infiltration. The RDA analysis showed that for S-type soil, biomass (54.30%) had the highest interpretation for its infiltration characteristics, while for N-type soil, they were coverage (39.30%) and gravel content (34.00%). (3) Among the three mainstream infiltration models, Horton model, Kostiakov model and Philip model, Horton model had the best fitting effect. The results could provide a useful reference for the study of water transport law of biological crusts in humid areas.

Abstract:In the context of achieving the goal of "carbon peaking and carbon neutrality", we should clarify the current situation of agricultural greenhouse gas emissions, simulate and predict the peak value, and provide a scientific basis for promoting low-carbon emission reduction of agriculture in Jiangsu Province. Based on the two types of carbon sources of agricultural material input and farmland soil utilization, the IPCC carbon emission coefficient method and inventory method were used to comprehensively calculate the carbon emissions of the planting industry in Jiangsu Province from 1990 to 2020. The Tapio decoupling model was used to analyze the decoupling relationship between agricultural carbon emissions and agricultural economic growth, and the carbon emissions from 2021 to 2060 were predicted based on the grey prediction model GM (1,1). The results showed that:(1) The carbon emissions from agricultural planting in Jiangsu Province reached 1 999.53 tons in 2020. From 1990 to 2020, it first increased, then decreased, then increased, and then tended to be stable. Carbon emissions from agricultural planting mainly came from farmland soil use, accounting for 77.73%~86.95% of carbon emissions, and 13.05%~22.27% of carbon emissions from agricultural inputs. (2) Chemical fertilizer was the most important source of carbon emissions from agricultural inputs, accounting for 69.15%~79.20%, followed by pesticides and agricultural film, and agricultural machinery, irrigation and tillage had relatively low proportion. (3) Rice was the main emission source of farmland soil use, accounting for 79.76%~87.23% of farmland soil use carbon emissions, followed by wheat and vegetables, while soybean, corn and cotton accounted for a relatively low proportion. (4) The decoupling relationship was dominated by weak decoupling and strong decoupling, indicating a slow growth or decreasing trend of the carbon emissions from agricultural planting with the increasing of gross domestic product of the planting industry. (5) Taking the carbon emissions data of agricultural planting from 1990 to 2020 (nearly 30 years) and 1999 to 2020 (nearly 20 years) as samples, it was predicted that the carbon emissions of agricultural planting in Jiangsu Province will continue to increase from 2021 to 2060, and will not reach the peak in 2060. Based on the carbon emissions data of agricultural planting from 2010 to 2020, the carbon emissions of agricultural planting in Jiangsu Province will continue to decrease from 2021 to 2060, and has reached its peak in 2020, indicating that the development of low-carbon green agriculture in Jiangsu Province has achieved initial results in recent years.

Abstract:In order to clarify the spatial and temporal variation and the influencing factors of soil moisture on mountain slopes in the humid subtropical climate zone, taking the mid-mountain concave slopes covered by coniferous forest in the Three Gorges reservoir area as the research object. The soil moisture data of 117 monitoring points at a depth of 0-70 cm in a 5-meter grid during 2019 to 2020 were analyzed by using classical statistics and geostatistics methods. And this study investigated the correlation between the statistical characteristics of soil moisture content and environmental factors and the spatial variability characteristics of soil moisture content in the catchment area of typical concave slopes under wet and dry conditions. The results showed that:(1) Soil moisture of all layers in the catchment area showed moderate variability (10%

Abstract:In order to clarify the characteristics of slope shape and slope changes in loess slope farmland under contour ploughing conditions, a simulated tillage experiment was conducted based on a combination of six slopes (3°, 5°, 10°, 15°, 20° and 25°) and five tillage intensities (6, 12, 18, 24 and 30 times). The influence of tillage intensity and slope gradient on the evolution characteristics of loess linear slope was discussed by using the needle method to measure the surface elevation before and after ploughing. The results showed that under the conditions of contour downward ploughing, the straight slopes with different slope gradients gradually evolved into "∽" type composite slopes with the increasing of tillage intensity. Under the same slope, with the increasing of tillage intensity, the slope toe extended, the projected slope length of the whole plot increased, the slope toe elevation increased significantly, the accumulation phenomenon was obvious, and the slope gradient decreased significantly. The elevation of the middle of the slope increased and gradually lifted the slope. The elevation and position of the new watershed formed at the top of the slope then decreased and moved downward, and the direct erosion rate gradually decreased and tended to be stable. The slope gradient controlled the distribution of soil during tillage by affecting the soil movement ability. Therefore, the greater the slope, the more obvious the change in slope shape after single tillage, and the greater the direct erosion rate. The results of the study were helpful for a deeper understanding of the impact of tillage erosion on the topography of slope farmland, and provide a theoretical basis for controlling soil erosion in slope farmland.

Abstract:In order to explore the effects of different proportions of fly ash composited with aeolian sandy soil on the fractal dimension and fertility of sand particles under drought stress and to provide a theoretical basis for fertility promotion of Mu Us sandy land, four fly ash levels (F0, F1, F2, and F3, accounting for 0, 1%, 5% and 10% of dry weight of aeolian sandy soil, respectively) and three water levels[W1, W2 and W3, accounting for (75±5)%, (55±5)% and (35±5)% of the field water capacity, respectively] were set up in the experiments, and a pot cultivation method was used for water control. The fractal dimension was used to reflect the particle size distribution of aeolian sandy soil under the action of water and fly ash. And the principle component analysis and hierarchical cluster analysis method were used to evaluate the fertility change of aeolian sandy soil under different treatments. The results showed that:(1) Under the same water condition, the fractal dimension of aeolian sandy soil increased with the increasing of fly ash proportion. (2) Under the same proportion of fly ash, the content of nitrate nitrogen (NO₃^--N) of aeolian sandy soil showed an increasing trend with the improvement of drought stress utilization efficiency. (3) The total nitrogen (TN) content of aeolian sandy soil was at low level under treatments of fly ash and drought stress. Nitrogen fertilizer application should be considered in the actual production process. (4) The comprehensive evaluation results of aeolian sandy soil showed that 10% composite ratio of 10% fly ash had good effect and it had certain applicability in drought situations.

Abstract:In order to explore the impact mechanism of the shear resistance of root-soil composite in the Three Gorges Reservoir's water-level fluctuation zone, this study took root-soil composite of Cynodon dactylon as the research object, and used the triaxial test to quantitatively analyze the influence of water content, dry-wet alternate times and root content on the shear resistance of root-soil composite. The results showed that:(1) With the increasing of dry-wet alternate times and water content, the soil shear resistance gradually deteriorated. The shear resistance of the root-soil composite with 13% water content was 0.12%~14.76% and 12.47%~21.14% higher than that of the soil with 18% water content and 23% water content, respectively. The shear resistance of the root-soil composite subjected to 6 and 3 cycles of dry-wet alternation was 6.31%~14.71% and 2.41%~8.19% lower than that subjected to one cycle of dry-wet alternation. (2) Root content could significantly affect the soil shear resistance, and the soil shear resistance with root content of 1.5 mg/cm³ was 0.86%~21.10% higher than that with root content of 0.5 mg/cm³. The internal friction angle increased by 0.09%~16.31%, and the cohesion increased by 2.27%~30.55%. (3) Water content was the dominant factor affecting the soil shear strength. The order of contribution to the shear resistance was water content (61.30%) > dry-wet alternate times (21.17%) > root content (8.28%). This study provided scientific reference for species screening, community construction, ecological construction of soil and water conservation, ecosystem reconstruction, and reservoir management in the water-level fluctuation zone of the Three Gorges Reservoir.

Abstract:Studying the runoff and sediment characteristics and trends of sandy rivers in arid and semi-arid regions is of great significance for water and sediment regulation and prediction in the basin. Based on the macro (micro) perspective, the characteristics and trends of sandy rivers in arid and semi-arid areas were studied in detail, in order to provide theoretical help for flow and sediment regulation and prediction in river basins. In this study, the umulative distance method, ITA method and ITA-CB method were used to calculate the inflow flow and sediment transport rate of Kezier Reservoir, meanwhile the characteristics and trends of flow and sediment transport rate were systematically analyzed from the three scales of intrayear, interannual and interdecade scales. The results showed that:(1) The distribution characteristics of flow and sediment were highly similar in the year, with the highest value in July and the lowest value in March and January, respectively, with strong volatility and obvious differences on the interannual scale. (2) The annual inbound flow in the past 58 years showed an upward trend with an increasing tendency, and in summer it showed an upward trend with a weakening tendency, among which the upward trend of the high-value area weakened, and it was necessary to pay attention to the extreme climate of drought. (3) The annual sediment transport rate showed an upward trend, and the trend characteristics under the quarterly scale showed a downward trend, among which the downward trend in summer and autumn tended to weaken, and it showed a tendency to strengthen in winter. Compared with traditional analysis methods, ITA and ITA-CB methods could effectively identify the microscopic trends within the sequence, and were more helpful for analyzing the changes of regional flow and sediment in detail.

Abstract:Taking the chestnut forest in Miyun District of Beijing as the research object, plant measures, engineering measures, and plant + engineering measures were set up to analyze the impact of different single and combined soil and water conservation measures on the runoff and sediment yield and the relationship between runoff and sediment on the slope, with the aim of providing scientific basis for the formulation of soil and water conservation measures in chestnut forests in Miyun District. The results showed that in terms of plant measures, the runoff and sediment reduction rate of Selaginella tamariscina treatment was 62.8% and 88.3%, respectively. The reduction effect of runoff and sediment of S. tamariscina treatment was better than that of coconut silk blanket, Cynodon dactylon and Zoysia japonica treatment. In terms of engineering measures, the runoff and sediment reduction rate of level terrace treatment was 83.2% and 92.9%, respectively, which was higher than that of fish-scale pits treatment. In terms of the combined measures, the runoff and sediment reduction rate of level terrace + S. tamariscina treatment was 86.7% and 96.1%, respectively, indicating the best effect of soil erosion prevention and control. The impact of different measures on runoff and sediment also depended on rainfall amount and intensity. In summary, the combined measures plant + engineering measures had slightly stronger control effects of runoff and sediment than engineering measures, but the difference was not significant. Therefore, on the basis of comprehensive consideration of economic and ecological benefits, it was recommended that engineering measures should be adopted to prevent and control soil and water loss in chestnut forests in this study area. Specifically, level terrace should be taken as the main soil and water conservation measures in the study area.

Abstract:High frequency (5 min) soil moisture probes and automatic weather stations were used to monitor the soil moisture change process and its response to rainfall on typical tea garden slopes and woodland slopes in the Three Gorges Reservoir Area. The regularity of soil moisture change in woodland and tea garden was clarified, and the impact mechanism of land use patterns and microtopography on soil moisture and rainfall storage was revealed. The results indicated that:(1) The soil moisture of the tea garden and woodland varied with the rainfall, and the soil moisture of woodland and tea garden varied with the depth in "W" and "S" shape, respectively. The annual variation coefficient of soil moisture decreased with the increasing of soil depth. The change of water content was at moderate level (10% < CV < 100%) in surface soil (10 cm), while it was at a weak variation level (0< CV < 10%) in deep soil (20-120 cm). (2) Furthermore, the results of One-way ANOVA showed that sand content in tea garden was significantly greater than that in woodland (p<0.05), while the clay content was less than that in woodland. The specific surface area of sand particles was small, and the water retention was poor. Therefore, the water storage capacity of each slope of woodland was obviously greater than that of tea garden. (3) The influences of slope position on soil moisture in woodland and tea garden were similar. Specifically, the seasonal variation of soil moisture on upper slope was smaller than that on middle and lower slopes, and was most evident in the 80-120 cm soil layer. The water content of the 80-120 cm soil layer on the upper slope was relatively stable, while it changed dramatically on middle and lower slopes. The impact of slope position on water storage recharge was shown as the recharge amount on the lower slope was greater than that on the middle and upper slopes. (4) Pearson correlation analysis showed that the soil water supplementary amount and rainfall were in a significant (p<0.01) positive correlation in tea garden and woodland. And the linear regression results showed that the determination coefficient R was greater than 0.81 except for the upper slope of tea garden, indicating a good fit between soil water supplementary and rainfall. These results could provide reference for the rational utilization of rainfall resources on tea garden slopes and regional soil erosion control in mountainous and hilly areas.

Abstract:Plant based sand fixing agents are environmentally friendly sand fixing agents mainly composed of plant material extracts. The feasibility of their application in sandy farmland was studied. Three plant-based sand fixing agents (Robinia pseudoacacia type, flax type, and sunflower type) and sandy soil were used as the research objects, and the same amount of water was sprayed as CK. Comparative experimental studies were conducted on the effects of different dosages on the formation of a consolidated layer of sand, compression resistance, wind erosion resistance, plant seed germination, and seedling growth. The results showed that:(1) When sprayed with black locust type, flax type, and sunflower type sand fixing agents on the surface of sandy soil, a consolidation layer with a thickness of 1 to 14 mm can be formed, and its average compressive strength is 206.21%, 147.51%, and 72.74% higher than CK. (2) All three plant-based sand fixation agents had significant sand fixation effects. As the dosage increases, the soil's resistance to wind erosion was significantly enhanced. At a dosage of 5 g/m², the wind erosion amount was the lowest, with a decrease of 65.92%, 58.33%, and 69.55% compared to CK, respectively; (3) Black locust type and flax type sand fixing agents had a promoting effect on wheat seed germination and bud growth, while sunflower type sand fixing agents had an inhibitory effect, and the inhibitory effect was obvious with increasing dosage. When the dosage reached 3 g/m², seed germination was significantly inhibited, and the germination rate was reduced by 62.50% compared to CK; When the dosage reached 4 g/m², root sprouting was significantly inhibited; When the dosage reached 2 g/m², the growth of buds was significantly inhibited. (4) The consolidation layer had a certain impact on the soil breaking of seedlings, with the black locust type sand fixing agent had the greatest impact. When the dosage reached 5 g/m², the emergence rate of wheat and alfalfa significantly decreased by 10.54% and 3.90% compared to CK. However, after the seedlings break through the consolidation layer, all three sand fixing agents had a certain promoting effect on the growth of wheat and alfalfa plants. Taking into account factors such as compressive strength, plant seed germination, and seedling growth, it has a good wind erosion resistance effect and no inhibitory effect on plants at the dosage of C3, C4, Y3, and Y4. This study provides a theoretical basis for the research and application of plant resource-based sand fixing agents, and provides a reference for the technology of wind erosion control of farmland soil.

Abstract:It is of great significance to investigate the effects of intercropping leguminous crops on soil moisture, nitrate nitrogen content and tree growth in young orchards for the improvement of soil fertility and sustainable development of dryland orchards on the Loess Plateau. Taking apple-soybean compound system in the loess hilly-gully region as the research object, the influence of different density of intercropping soybean on fruit tree growth were evaluated by measuring the changes in water and nitrate nitrogen content, as well as the nitrogen content and physiological indicators of fruit tree leaves in the experimental plot during the entire reproductive period of soybean planting. The results showed as follows:(1) Compared with clear tillage orchard, medium density intercropping had a certain effect on the soil moisture content of orchard before soybean flowering, while high density intercropping increased the water consumption between rows and significantly reduced the soil moisture content. (2) The relative accumulation of nitrate nitrogen in different soil layers gradually decreased and the distribution gradually balanced with the reproductive period of soybean, and there was no significant difference in the total nitrate nitrogen accumulation of soil between treatments. (3) Both medium and high density intercropping could effectively increase the leaf nitrogen content of fruit trees and promote fruit trees growth. Soil water content and leaf nitrogen content of medium density soybean intercropping increased by a maximum of 17.6% and 8.04% respectively. Therefore, medium density soybean intercropping had more advantages in dryland apple orchards on the Loess Plateau.

Abstract:Conducting landslide susceptibility analysis is the foundation for formulating reasonable geological disaster prevention and control plan, which is of great significance for disaster prevention and reduction. Taking Nujiang Prefecture as the research area and slope unit as the evaluation unit, nine factors including elevation, slope, slope aspect, NDVI, rainfall, lithology, distance from fault and distance from road were selected as evaluation factors. Information content (I) model, deterministic coefficient (CF) model and I-LR and CF-LR coupling models were used to evaluate landslide susceptibility. The accuracy of the four models was verified. The results showed that:(1) In the CF-LR model, the proportion of landslide points falling into high and extremely high prone areas was the largest, accounting for 88.77%, the density of landslide points (0.309 2) was the largest, which was higher than that of I model (0.285 4) and CF model (0.277 6). (2) The extremely high and highly prone areas mainly developed in the Nujiang River, Dulong River, Lancang River and Tongdian River. The middle prone area was mainly distributed in the eastern part of the study area. The low and very low susceptibility prone area was mainly distributed in the northern, central and western edge of the study area. (3) According to the results based on Sridevi Jadi empirical probability method and ROC curve, the prediction accuracy of CF-LR model was higher than that of the other three models.

Abstract:Land use and vegetation cover are direct manifestations of human activities in transforming nature. In order to quantitatively assess the impact of human activities on soil erosion, this study focuses on Changting County, a typical red soil erosion-prone area in southern China. Using remote sensing images from 11 years between 1988 and 2020 with 3- or 4-years interval, the USLE model was applied to evaluate the spatiotemporal characteristics of soil erosion in the county over the past 30 years, and the quantitative impact of different land use and Fractional Vegetation Cover (FVC) changes on soil erosion was analyzed. The results showed that:(1) The severe soil erosion in Changting County is mainly concentrated in the central areas of the county, including Hetian Town, Sanzhou Township, and Cewu Township. Over the past 30 years, the intensity of soil erosion showed an increasing trend followed by a decreasing trend. From 1988 to 1994, the situation of soil erosion became increasingly severe, with a soil erosion rate as high as 30.49% in 1994. Since the mid-1990s, the situation gradually improved, and by 2020, the soil erosion rate had decreased to 6.22%. (2) During the two periods of 1988-1994 and 1994-2001, the area of forest land converted to bare land was the largest, resulting in an average increase in soil erosion of about 93% for each period. During the two periods of 2001-2010 and 2010-2020, the area of bare land converted to forest land was the largest, resulting in an average reduction in soil erosion of about 73% for each period. (3) For over 30 years, the FVC in Changting County has shown a decreasing trend followed by an increasing trend. The average FVC decreased from 44% to 35% between 1988 and 1994, after which it began to increase. As of 2020, the FVC has increased to 79%. The soil erosion amount was inversely proportional to the FVC, and the impact of FVC reduction on soil erosion was greater. On average, for every 1% decrease in FVC, the soil erosion increased by 74 900 tons, while for every 1% increase in FVC, the soil erosion decreased by 37 500 tons. (4) The FVC in Changting County was negatively correlated with soil erosion intensity, and the sensitivity to soil erosion was positively correlated with slope. Under low slope conditions, soil erosion changed more uniformly with FVC, but under high slope conditions, when FVC was less than 60%, the sensitivity to soil erosion was high. For each 10% increase in FVC, the average soil erosion modulus in areas with a slope greater than 15° was reduced by 262.73 t/(km²·a). This study helps to analyze the spatiotemporal changes of soil erosion in Changting County over a long time series and the impact of human activities on soil erosion, providing important scientific support for future land use planning and ecological protection in Changting County.

Abstract:In order to quantitatively study the relationship between vegetation cover and soil conservation, as well as the impact of vegetation cover on soil conservation, this study selected the top ten tributaries as the research area, and used trend analysis, spatial autocorrelation analysis, InVEST model to focus on analyzing the temporal and spatial changes of vegetation cover and soil conservation and the effect of vegetation cover change on soil conservation in the top ten tributaries area from 2000 to 2020. The results showed that:(1) During the study period, the vegetation coverage in the top ten tributaries area showed an increasing trend. (2) From 2000 to 2020, the soil conservation capacity increased with the increasing of vegetation cover, which indicated that the increase of vegetation cover had a significant inhibitory effect on soil erosion and had a significant promoting effect on soil conservation service function. (3) Vegetation coverage and soil conservation had local spatial autocorrelation, with Moran's I<0, but the correlation coefficient gradually increased from 2000 to 2020. In terms of the spatial distribution, there were significant differences in correlation distribution. 'High-high' and 'low-low' were sporadically distributed in the middle Kubuqi windy desert area and the upstream hilly and gully area. 'High-low' and 'low-high' distributed in the upstream hilly and gully area and the downstream alluvial plain area. It was mainly because in the upstream hilly and gully area, there was higher altitude and stronger soil conservation ability but lower vegetation coverage. The downstream alluvial plain area was mainly farmland ecosystem, with a high NDVI in the growing season, but poor soil erosion resistance and weak soil conservation ability. Through the analysis of the vegetation cover change and soil conservation evolution, as well as their spatial heterogeneity and correlation in the ten tributaries areas, it indicated that the increase of vegetation cover had a promoting effect on soil conservation to a certain extent, and the results also could provide a certain reference for the soil erosion control work in the study area.

Abstract:To investigate the evolution pattern and drivers of soil erosion in the Qingyi River watershed of Anhui Province, the InVEST model was used to investigate the soil erosion characteristics of the watershed from 2000 to 2018, quantify the soil erosion conditions under different land use types, elevations, and slopes, and analyze the factors influencing soil erosion in the watershed with the help of a geographic probe. The results showed that:(1) The average soil erosion modulus in the watershed was 15.29, 14.14, and 10.74 t/(hm²·a) in 2000, 2010, and 2018, respectively, and the total erosion was 1.08×10⁷, 1.00×10⁷, and 0.76×10⁷ t, respectively, showing a gradually decreasing characteristic. (2) Soil erosion in the watershed varied significantly in space, showing a distribution pattern of low in the north and high in the south. (3) The size of soil erosion modulus of different land use types showed that bare land>grassland>forestland>cultivated land>construction land>water bodies, and the erosion of forest land in the watershed was the largest, accounting for 73.71% of the total erosion. (4) Topographic factors had significant effects on soil erosion in the watershed, and slope was the dominant factor of soil erosion in the Qingyi River watershed. The explanatory power of the interaction between factors on soil erosion was greater than that of single factors, among which the synergistic effect of slope with annual precipitation and land use was the strongest, reaching 22.93% and 22.29%. (5) Soil erosion could be effectively reduced by slowing the slope and increasing grassland and woodland cover in slope areas. The results of the study provide a basis for clarifying the distribution pattern and driving factors of soil erosion in the Qingyi River basin, and can provide a basis for decision making to promote soil and water conservation management and improve ecological benefits in the Qingyi River basin.

Abstract:In order to systematically reflect the soil erosion characteristics of typical water erosion small watershed in Mollisols region, in this study, NDVI was calculated based on continuous Landsat TM/OLI images. Based on the optimized soil and land use parameters, combined with field surveys, the average soil erosion modulus and erosion deposition distribution pattern in the Guangrong Small Watershed of Helen City from 2000 to 2021 were simulated using the China Soil Loss Equation (CSLE) and the Unit Flow Weighted Erosion Deposition (USPED) model, respectively. Meanwhile, the spatial distribution of snowmelt erosion in spring 2017 was simulated by the snowmelt erosion model (SHI), and the causes of erosion patterns in the small watershed were comprehensively analyzed. The results showed that from 2000 to 2021, the CSLE simulation found that the average soil erosion modulus was 5.57 t/(hm²·a), and the average soil loss was 0.55 mm/a. The erosion on slope was relatively small, belonging to slight erosion[0~2 t/(hm²·a)]. The middle of the slope was in the very strong erosion and strong erosion class, and the erosion contribution was mainly from the slope 2°~6° area, accounting for 79.56% of the total erosion amount. USPED simulation found that 78.11% of the small watershed area was eroded or deposited, of which the erosion area accounted for 24.89% of the watershed area, and the average erosion modulus was 9.40 t/(hm²·a), and most of them concentrated in the erosion gullies at the middle and bottom of the slope. The deposition area accounted for 53.22% of the watershed area, and the average deposition modulus was -4.39 t/(hm²·a). Affected by changes in rainfall, the average erosion modulus of small watershed showed an overall upward trend from 2000 to 2021, with erosive rainfall concentrated in July and August. The results of the SHI model showed that the average erosion modulus of the small watershed was 1.65 t/(hm²·a) in the spring of 2017, accounting for 32.07% of the total erosion in that year, which was higher than the snowmelt erosion modulus calculated based on the snowfall data. The results of the study could provide a scientific basis for simulation and scientific prevention and control of soil erosion in typical Mollisols small watershed in Northeast China.

Abstract:In order to accurately simulate the dynamic process of soil erosion in the Dongting Lake basin and quantitatively evaluate its contribution of influencing factors, the sediment transport restriction model (TLSD) was coupled on the basis of the Chinese soil erosion equation (CSLE) to realize the analysis of the whole dynamic process of soil separation-transport-sediment, and trend analysis and geographic detector methods were used to explore the spatial and temporal characteristics and influence mechanism of soil erosion in the Dongting Lake Basin from 1980 to 2020. The results showed that:(1) The simulation and measured values of annual sand transport in each hydrological station were well matched by the coupled CSLE-TLSD model (R²=0.56). (2) From 1980 to 2020, the average annual soil erosion modulus of Dongting Lake Basin was 5.09 t/(hm²·a), and both the erosion modulus and area showed a downward trend on the whole. The areas with significant erosion improvement accounted for 22.60% of total basin area, while the area with significant erosion intensification accounted for only 2.69%. (3) With 2005 as the mutation point, the annual total erosion showed a trend of first decreasing and then increasing. (4) Around 2005, the dominant factor leading to soil erosion change changed from land type change to annual rainfall change. In conclusion, soil erosion in the Dongting Lake basin showed a general trend of erosion area shrinkage, while local deterioration trended, among which extreme rainfall events and fruit forest development were the main reasons for the intensification of erosion.

Abstract:Under the dual constraints of "dual carbon" goal and ecological environment protection, it is of great significance to study the interaction between carbon emissions caused by land use change and the value of ecosystem services to promote the realization of carbon neutrality goals and regional high-quality development. Selecting the main urban area of the Changzhutan urban agglomeration as the research object, based on the data of land use, energy consumption and socio-economy in the five periods from 2000 to 2020, the grid analysis method and bivariate spatial autocorrelation model were comprehensively used to explore the temporal and spatial evolution characteristics and interaction between land use carbon emissions and ecosystem service value. The results showed that:(1) From 2000 to 2020, different degrees of transfer occurred among various land use types, among which cultivated land and forest land decreased by 392.77 km² and 268.10 km², respectively, and construction land increased by 661.80 km². (2) From 2000 to 2020, the net carbon emissions of Changzhutan urban agglomeration was positive, and the overall performance was carbon emissions, and the net carbon emissions increased significantly from 1 099.84×10⁴ t to 4 109.21×10⁴ t. The carbon emission intensity showed the spatial distribution characteristic of high center and low edge. (3) ESV decreased slowly from 392.06×10⁸ yuan to 292.86×10⁸ yuan, with a decrease of 5.34%. The ESV intensity showed the spatial distribution characteristic of high in the Xiangjiang River basin and low in the surrounding area. (4) There was a significant negative correlation between land use carbon emission intensity and ESV intensity, and the local agglomeration types of them could be divided into four types, which were high and high, low low, low high, high and low, respectively, and their spatial distribution ranges were different. The results provide a reference for revealing the spatiotemporal relationship between carbon emissions caused by land use change and the value of ecosystem services.

Abstract:Under the background of "four water and four regulations", scientifically quantifying the future water conservation in towns or small basins in a changing environment is an important foundation for water resource management, water conservancy planning and water ecological protection. The scale transformation of water conservation is one of the difficulties in the study of ecological hydrology at present, and the research of higher fine scale is an important entry point of scale transformation. In this paper, taking Bahe River Basin at the northern foothills of Qinling Mountains as the research area, SWAT model, CA-Markov model, ArcGIS and RClimDex were used to evaluate the monthly discharge simulation capability of the NEX-GDDP-CMIP6 high-resolution dataset, and the optimal climate model was selected to simulate the future land use change. The evolution trend of water conservation in the Bahe River Basin in the next 30 years was analyzed in order to provide basic data for ecological protection, water resource management and land use protection in the Qinling Mountains. The results showed that:(1) NEX-GDDP-CMIP6 high-resolution data sets, such as ACCESS-CM2, ACCESS-ESM1-5 and CanESM5, had better simulation effect on the mean monthly flow, but worse simulation effect on extreme flow. NESM3 climate model has better simulation effect than other 8 climate models. (2) NESM3 climate model underestimated the extreme precipitation and overestimated the duration of dry days, and it had higher ability to simulate monthly scale precipitation data than annual and daily scales. (3) Kappa coefficient test showed that CA-Markov model had good applicability in land-use change in the Bahe River Basin. (4) Under the combined background of land use and climate change, water conservation in the Bahe River Basin showed a decreasing trend from 2023 to 2050. The results were of great significance for water resources management in the Bahe River Basin, water conservation and ecological protection in the Qinling Mountains.

Abstract:Baseflow is an essential part of river water resources in arid areas, which play an important role in maintaining streamflow and ecological security in the basin. Investigation on the change characteristics of baseflow and its responses to precipitation in Wuding River Basin is of great significance for optimizing the allocation of water resources on the Loess Plateau. Based on daily precipitation and runoff data of Wuding River Basin from 1960 to 2019, and combined with digital filtering method, wavelet transform, double cumulative curve and elastic coefficient method, the study analyzed inter-annual and intra-annual variation characteristics of precipitation and baseflow depth, discussed the time-frequency relationship between precipitation and baseflow depth as well as the time lag effect of baseflow on precipitation, and clarified the change direction of precipitation-baseflow relationship. The result showed that annual baseflow depth displayed a highly significant downward trend (p<0.001), and annual baseflow index showed a non-significant upward trend (p<0.1), with perennial average values of 23.83 mm and 0.67, respectively. The values of baseflow depth and baseflow index were higher in spring and autumn, and lower in summer and winter. The control ability of precipitation on baseflow in summer and autumn was stronger in both high and low energy regions than that in spring and winter. The average annual lag time of baseflow to precipitation was 3.2 d, and the average monthly (May-October) lag time was less than 7 d. In the past 60 years, baseflow reserves in the watershed increased by more than 7 times. The relationship between precipitation and baseflow depth changed twice, the change points were 1971 and 2000, respectively. The sensitivity of baseflow to precipitation weakened gradually after 2000, and their relationship evolution became more stable. The results would provide theoretical support for sustainable development and utilization of water resources in the middle reaches of the Yellow River.

Abstract:Exploring the relationship between grassland vegetation patterns and soil water conservation function plays an important role in evaluating and effectively utilizing soil and grassland vegetation resources. The study was conducted on the alpine grassland ecosystem in the Yellow River source area, a model of soil water conservation function was constructed using MODIS data and its spatial and temporal variation characteristics were explored. The spatial and temporal variation patterns of grassland vegetation were clarified, and the seasonal variation and spatial distribution characteristics of their coupling relationship were explored based on the theory of coupling coordination. The results showed that:(1) Soil water conservation function index and comprehensive vegetation index showed an increasing trend in all seasons from 2000 to 2021, and the seasonal average values were higher in summer and autumn than those in spring and winter. (2) The coupling coordination of soil water conservation function-vegetation (SWCF-VEG) basically showed an increasing trend in all seasons from 2000 to 2021, and the spatial distribution of the coupling coordination values were significantly varied among different soil layer depths, and the seasonal performance followed the order of summer>autumn>spring>winter. (3) The coupling coordination of SWCF-VEG showed an increasing trend for each grassland type in all seasons from 2000 to 2021. The mean values of coupling coordination for various soil depths in temperate grasslands were the maximum in all seasons, and the values of 10-20 cm were greater than those of 0-10 cm for each grassland type in summer, autumn and winter. The coupling coordination development types varied among grassland types in different seasons. The study could provide an efficient and quantitative spatiotemporal analysis method for the coupling relationship between grassland vegetation and soil water conservation function in the Yellow River source area, and the results could be the basis for the sustainable development of vegetation-soil in grassland.

Abstract:Arbuscular mycorrhizal (AM) fungi can coexist with wetland plants and play an important role in the restoration and maintenance of wetland ecosystem. However, the distribution and influencing factors of soil AM fungal community under different environmental conditions in wetland ecosystem still need to be clarified. Therefore, this study used high-throughput sequencing technology to explore the effects of water level and vegetation type on the community structure and diversity of soil AM fungi in Poyang Lake wetland. Two typical plant communities (Triarrhena lutarioriparia and Persicaria hydropiper) under different water levels (high and low water level) were chosen to compare the difference of the community structure and diversity of AM fungi among different environmental conditions. The relationship between AM fungal community and soil physicochemical properties was analyzed. The results showed that the OTU number of AM fungi ranged from 21 to 38. Both water level and vegetation type affected the OTU number of AM fungi in Poyang Lake wetland. The OTU number of AM fungi was higher under high water level than that under low water level, and it was higher in P. hydropiper community than that in T. lutarioriparia community. The identified genera of AM fungi were Glomus, Claroidoglomus and Paraglomus. Among them, Glomus was the dominant genus, accounting for more than 85%. And the relative abundance of Glomus was significantly higher under high water level, compared with low water level, while it was significantly higher in T. lutarioriparia community, compared with P. hydropiper community (p<0.05). The AM fungal diversity indices (Simpson and Shannon index) were affected by water level, vegetation type and their interaction (p<0.01). Under low water level, there was no significant difference in AM fungal diversity indices between different communities, but under high water level, the AM fungal diversity indices in P. hydropiper community was significantly higher than that in T. lutarioriparia community (p<0.05). Water level had a higher effect on community structure of soil AM fungi than that of vegetation type, and vegetation type significantly affected AM fungal community structure only at low water level. Correlation analysis showed that there was no significant relationship between AM fungal diversity indices (Shannon and Simpson index) and soil factors. Dominant genera Glomus and OTU number were significantly and negatively correlated with soil water content at low water level (p<0.05), while Glomus was significantly and positively correlated with soil pH at high water level (p<0.05). Hence, there was a threshold effect of soil water content on Glomus in wetland ecosystem. The results of the present study could provide scientific guidance for the restoration of degraded wetland ecosystem.

Abstract:Agricultural irrigation is the main way of water consumption in arid and semi-arid areas of north China. The level of agricultural water-saving directly determines the amount of regional available water resources. In order to explore the level of agricultural water saving in the farming-pastoral ecotone in north China, we took the farming-pastoral ecotone of Inner Mongolia as the research object. By combining analytic hierarchy process (AHP) with entropy weight method and fuzzy comprehensive evaluation, representative indicators reflecting the characteristics of agricultural water use in the agro-pastoral ecstatic zone were selected to construct an agricultural water-saving comprehensive evaluation system, and a comprehensive evaluation of agricultural water-saving in the agro-pastoral ecstatic zone in Inner Mongolia in 2020 was carried out. The results showed that there was a great difference in agricultural irrigation water consumption among counties in the agro-pastoral ecotone of Inner Mongolia, and the overall trend was higher in the east than in the west. The irrigation water consumption ranged from 582.41 m³/hm² to 4 905.86 m³/hm², and the utilization efficiency of irrigation water ranged from 51% to 84%. The comprehensive evaluation score of agricultural water-saving irrigation in all counties was between 2.26 and 3.67, and the overall water consumption level was above average. In 29 counties, good proportion was 44.80%, and medium proportion was 55.20%. Compared with crop water use efficiency (WUE), the constructed comprehensive evaluation system can more truly reflect the actual situation of agricultural water use in the farming-pastoral ecotone. The areas with medium level of agricultural water-saving irrigation still need to develop water-saving measures to improve the utilization efficiency of agricultural water resources.

Abstract:The spray seeding substrate is an important material for the rehabilitation of mine slopes but is prone to cause problems of water and fertilizer loss when washed away by rainfall. To improve the water and fertility retention capacity of the spray seeding substrate, water-retaining materials based on mycorrhizal bran, vinyl acetate, and acrylic acid were prepared and their effects on water and fertility retention and phytoremediation of the modified spray seeding substrate were investigated by simulated rainfall washout. The results showed that the water-retaining material absorbed 123.94 g/g of water in distilled water and 84.36 g/g of water in 0.9% sodium chloride solution at an m (bacterium bran)/m (acrylic acid) ratio of 1/3, a neutralization level of 80%, a crosslinker dosage of 0.09 g, an initiator dosage of 0.36 g and a vinyl acetate dosage of 6 mL. The water-retaining material significantly improved the scour resistance and phytoremediation of the spray seeding substrate and the fibers enhanced the effectiveness of the water-retaining material. The water-retaining material reduced runoff by 18.57% in the flush-evaporation cycle and extended the initial production time; reduced nitrate, ammonium, and total phosphorus losses by 15.89%, 56.52% and 58.21% respectively; increased ryegrass germination rate, survival rate and dry weight by 76.19%, 48.45% and 33.33% respectively; increased soil total N, P, and K content by 77.48%, 33.33% and 60.66% respectively; the water content of the inter-root spray seeding substrate increased by 30.50% compared to the control. The results of the study provide a theoretical basis for solving the problem of water and fertilizer loss during the rehabilitation of mine slopes with a spray seeding substrate.

Abstract:In order to explore the most suitable water and nitrogen system in salinized farmland under the condition of subsurface drainage, a 2-year field experiment was carried out in the hidden pipe layout area of Hetao irrigation district. In the experiment, we set three irrigation levels, including low water (120 mm, I1), medium water (210 mm, I2) and high water (330 mm, I3) as well as three nitrogen levels of low nitrogen (0 kg/hm², N1), medium nitrogen (105 kg/hm², N2) and high nitrogen (210 kg/hm², N3). The effects of different water and nitrogen combinations on soil desalination rate, water and nitrogen utilization efficiency, yield and quality of sunflowers were analyzed. The results showed that under the condition of subsurface drainage, the desalination effect of I3N2 treatment was the best, with an average increase of 5.82% in desalination rate compared to other water nitrogen treatments. Under high water (high nitrogen) conditions, the yield increased with the increasing of nitrogen application amount (irrigation amount), among which the yield of high water and high nitrogen (I3N3) was the highest, with an average of 5 129.72 kg/hm². Under the same irrigation amount, the utilization efficiency of irrigation water was the highest at high nitrogen application (N3), and the higher the nitrogen amount, the lower the productivity of fertilizer. Under low water (I1) and medium water (I2) conditions, high nitrogen (N3) level was the most conductive for synthesis of seed protein and essential amino acid. Under the conditions of high water (I3), medium nitrogen level (N2) was beneficial to the synthesis of seed protein and essential amino acids, while low nitrogen level (N1) was most beneficial to the synthesis of seed crude fat. At each irrigation level, the contents of protein and essential amino acid in medium water (I2) and high water (I3) treatments were generally higher than those in low water (I1) treatments, while the content of crude fat was generally lower than those in low water (I1) treatments. Based on principal component analysis and membership function comprehensive evaluation, it was found that high water and medium nitrogen treatment (I3N2), with an irrigation amount of 330 mm and a nitrogen amount of 105 kg/hm², was the appropriate combination of water and nitrogen in subsurface farmland. The results could provide a theoretical basis for the formulation of scientific water and nitrogen system in the subsurface farmland in Hetao irrigation district.

Abstract:To explore the fractal distribution of surface soil particle size, organic carbon content of different particle size and the characteristics of carbon management index as well as their relationship in the desert steppe, 4 kinds of typical communities in Huamachi Town, Yanchi County, Ningxia Hui Autonomous Region, including Caragana korshinskii, Artemisia ordosica, Stipa breviflora and Agropyron mongolicum, were selected as the research objects. Using surface soil (0-5 cm) under typical vegetation canopy and intercropping habitats, the dynamic changes and their correlations of organic carbon content of different particle size and soil carbon pool in different vegetation surface soils were analyzed. The results showed that:(1) The distribution of soil particle size of the four kinds of typical communities showed a "single peak" shape, soil particle concentrated in the range of 2~250 μm, the fractal dimension D in the range of 2.56 to 2.63, the content of particle within 100~500 μm was the main reason for significant differences between vegetation types. (2) The organic carbon content under the canopy of four typical vegetation types was greater than that of intercropping habitats, the organic carbon content of thick sand >250 μm was the highest, the organic carbon content of different particle size components varied significantly between the shrub and herbage vegetation (p<0.05). (3) The soil TOC and AOC contents of the four typical vegetation types were all higher under canopy than those of intercropping habitats. TOC varied significantly among different communities. The carbon pool activity (A) and carbon pool management index (CPMI) under the canopy of shrub communities were relatively higher than those of intercropping habitats. Various indicators varied greatly among different communities due to different habitats, indicating that different typical vegetations played different roles in the carbon pool cycling mechanism, and enhanced soil carbon sink function with different degrees. (4) The relationship between soil particle size fractal and carbon pool stability was complex. Fine silt with 2~50 μm was an inorganic colloid of soil organic carbon. The increasing of its content significantly increased the opportunity for soil particles and organic carbon to form organic-inorganic cement, which was of great significance for maintaining soil structure and the stability of organic carbon pool. The research results indicated that appropriate vegetation restoration measures had certain reference value for maintaining the stability of soil particles and soil organic carbon pools in desert grassland.

Abstract:In order to gain a detailed understanding of the soil erosion status in the dry-hot valley region, in this study, the measured data from runoff plots in dry-hot valleys were widely collected, organized and analyzed, thus the soil erosion modulus under the average slope of the local main land use types were estimated and compared with the allowable soil loss amount. The results indicated that:(1) The soil erosion modulus of shrub-grass land, agricultural land, orchard land and bare land under the standard slope length and slope gradient was 110.88, 389.58, 320.66 and 507.87 t/(km²·a), respectively, indicating that soil erosion modulus in the bare land was the highest, followed by the agricultural land, orchard land and shrub-grass land. (2) Soil and water conservation measures such as lockdowns, horizontal terraces, terraces and hedgerows all played an important role in reducing soil erosion with the average reduction of 72%. (3) The soil erosion modulus of the main land use types, especially agricultural land and orchard land in all the dry-hot valleys, were significantly higher than the allowable soil loss under the local average slope, indicating that the soil erosion situation in the region was still quite severe. This study could help to further deepen the understanding of the soil erosion principles in the dry-hot valleys and provide important technical supports for subsequent soil erosion control and optimal allocation of soil and water conservation measures.

Abstract:In order to reveal the pores complex structure of biochar-amended soils and its influencing factors, the saline/sodic soil in the coastal reclamation area of Jiangsu Province was taken as the research subject. In this study, the surface soils (0-20 cm) were amended by thoroughly mixed biochar with three application rates (0, 2% and 5% by mass of soil, respectively) in a completely randomized design. After harvesting rice in October each year, the surface layer (0-20 cm) of undisturbed soils was taken using a plastic ring and the CT pore series of the soil was obtained through Micro-CT scanning. Based on multifractal detrended fluctuation analysis and data rearrangement, the influence of biochar addition on the multifractal characteristics and their source of CT-porosity series was analyzed. The results showed that the complexity of pore series for each treatment increased with year. Compared with 0 and 5% biochar treatments, the complexity of CT pore series in 2% biochar treatments increased by 7.54% and 5.28%, respectively. Both probability density function and long-range correlation influenced the multifractal characteristics of CT pore series. Long-range correlation between pore and space was the main influencing factor. The addition of biochar made the pore fractal characteristics more susceptible to the influence of microbial activities in soil. This study could provide a theoretical basis for analyzing the pore structure of saline soil with biochar.

Abstract:Rainfall intensity and soil and water conservation tillage measures have a significant impact on slope runoff, erosion sediment and soil trace elements. We studied the loss characteristics of Cu, Mo and Zn in tobacco planting red soil under different rain patterns, land preparation methods and cover conditions through field rain-fall observation methods. The results showed that:(1) Rainfall intensity had a significant effect on the loss of the three trace elements in the tobacco planting soil. With the increasing of rainfall intensity, the total loss of Cu, Mo and Zn followed the order of heavy rain>moderate rain>light rain. (2) Although straw covering and cross slope planting measures could effectively reduce erosion sediment caused by erosive rainfall, the enrichment ratio of Cu, Mo and Zn in sediment increased. (3) Compared with the treatment without straw mulch, Cu, Mo and Zn in runoff decreased by 44.99%, 47.42% and 62.24%, respectively, and the total loss of trace elements in sediment decreased by 67.35%, 56.88% and 67.85%, respectively, and straw mulching treatment had a significant effect on the reduction of total loss of trace elements (p<0.05). (4) Cu, Mo and Zn in the runoff of the cross slope planting treatment decreased by 43.31%, 46.39% and 45.62%, respectively, compared with the slope planting treatment. The three trace elements in the sediment decreased by 66.34%, 53.95% and 59.66%, respectively. The cross slope planting treatment significantly reduced the loss of the three trace elements (p<0.05). (5) The total loss of Cu, Mo and Zn in sediment was significantly higher than that in runoff, and the loss of Cu, Mo and Zn in runoff and sediment followed the order of Zn>Cu>Mo. This study results could provide theoretical basis and data support for effectively reducing and controlling the loss of trace elements caused by soil and water loss of typical tobacco planting red soil in southwest China and for soil and water conservation in tobacco planting red soil.

Abstract:In order to explore the effects of combination of conservation tillage and straw returning on water storage during fallow period, temporal and spatial variation of soil moisture during growth period, seasonal variation of water storage, yield and WUE of maize, the located experiment was conducted by setting 6 treatments of different tillage methods (no-tillage, sub-soiling and deep plowing) combined with straw returning (100% straw returning, no straw returning) in Jinzhong of Shanxi from 2016 to 2018. The results showed that:(1) The difference in soil water storage under different tillage treatments during spring maize winter fallow period was significant, and water storage had a decreasing trend along with time delay. The soil water storage of no-tillage and sub-soiling treatments increased by 10.4 mm and 9.3 mm, respectively, compared with deep plowing. During the whole growth stage of maize, the soil water storage of no-tillage and sub-soiling was 4.8% and 1.2% higher than that of deep plowing. (2) The order of average soil water content for two years was no-tillage > sub-soiling > deep plowing, the average soil water content of each treatment was 23.0%, 21.8% and 21.5%, respectively. The vertical variation of soil water content under different tillage methods varied greatly during different growth periods in wet year, and while the variation in drought year was small. (3) The combination of no-tillage and 100% straw returning had the highest yield and WUE of maize, the 2-year average yield and WUE was 12 679.9 kg/hm² and 25.8 kg/(hm²·mm), respectively. The combination of deep plowing and 100% straw returning had the lowest yield and WUE. Regardless of whether straw was returned to the field or not, no tillage and sub-soiling were better than deep plowing on soil water conservation in winter fallow period, soil moisture status in growth period, yield and WUE of spring maize. No-tillage and sub-soiling tillage under straw returning had good effect on water collection and conservation in maize field. The combination of no-tillage and 100% straw returning had the best effect, it could be promoted and applied in spring maize production in Jinzhong area.

Abstract:In order to provide scientific theoretical basis for green manure utilization and nitrogen fertilizer application in southern rice, based on the field localization experiment in 2016, the influence of different nitrogen application rates (N0:no nitrogen application; N50:50% reduction in nitrogen; N100:conventional nitrogen; N150:50% increase in nitrogen application) on yield, nutrient uptake characteristics and nitrogen efficiency of double-cropping rice were explored in the two modes of fallow (F) and green manure (G). The results showed that compared with the fallow mode, the green manure mode of winter planting increased the yield of early and late rice under these four different nitrogen levels, and the yield of early and late rice increased by 8.0% and 5.7% on average. In both modes, the yield of early rice increased firstly and then decreased with the increase of nitrogen application, while the increase of late rice showed an upward trend. The green manure model of winter planting also increased the accumulation of nitrogen (N), phosphorus (P), and potassium (K) in the aboveground part of the plant and the partial productivity of nitrogen fertilizer. With the increase of nitrogen application, the nutrient harvest index and nitrogen fertilizer utilization rate of early and late rice in these two modes mostly showed a downward trend, and the high-level nitrogen fertilizer treatment (N150) reduced the accumulation of aboveground K elements in the early rice season. There was a significant positive correlation between early and late rice yields and N, P and K accumulation, and the decrease of high nitrogen treatment (N150) K uptake in the two modes was associated with the decline of early rice yield. Comprehensive consideration combined with the fitting analysis of rice yield and nitrogen application rate, nutrient absorption, and utilization, etc., the suitable application range of nitrogen fertilizer in early rice season was 150.0 to170.3 kg/hm² under the fallow mode, and 75.0 to 122.8 kg/hm² in early rice season under winter green manure mode. Therefore, in the double-cropping rice area of southern China, planting green manure in winter can increase the absorption of N, P, and K elements in rice, and can reduce nitrogen fertilizer without reducing the yield of double-cropping rice in the early rice season, which is of practical significance for achieving efficient rice production.

Abstract:In order to explore the suitable irrigation system of Korla Fragrant Pear orchard under labor-saving cultivation mode, based on the two-year field test data of Fragrant Pear under four irrigation quotas (3 750, 5 250, 6 750 and 8 250 m³/hm²), the AquaCrop model parameters were determined through using canopy coverage, soil water content, evapotranspiration (ET_a) and yield index. Different irrigation scenarios were set up, and the yield, water use efficiency and yield were comprehensively considered, AquaCrop model was used to optimize the irrigation system of fragrant pear. The yield of Y2W3 treatment was 3.87%~16.86% higher than that of other treatments, and the water use efficiency of Y2W3 treatment was 2.88%~27.20% higher than that of other treatments. The evaluation indexes of determining coefficient (R²), root mean square Error (RMSE), standard root mean square error (NRMSE), the Willmott's index of agreement (d) and Nash Sutcliffe efficiency (NSE) of the simulated and measured results of AquaCrop model showed that the canopy coverage R² ranged from 0.89 to 0.93, the range of soil water content d was 0.92~0.98, the range of ET_a RMSE was 1.06~1.61 mm/d. The AquaCrop model predicted 15 different scenarios, and the irrigation system with irrigation quota of 7 200 m³/hm², irrigation frequency of 11 times and irrigation cycle of 14 days performed best, with a yield of 6 793.62 kg/hm², water use efficiency of 10.90 kg/(hm²·mm) and irrigation water use efficiency of 1.03 kg/m³. AquaCrop growth model could be used for yield prediction and field water management of fragrant pears, and the results could provide a basis for the applicability selection of surface drip irrigation technology.

Abstract:Quantifying the response relationship of drought statistical data and climatee factors is of great significance for ensuring food security. Aiming the agricultural drought-affected rate in 13 grain producing provinces from 1980 to 2019, the responses of the actual disaster conditions to the climatic factors of different months were constructed by using ensemble empirical mode decomposition (EEMD), and then the possible relationship between important climatic factors and large-scale atmospheric-ocean indices (LAOI) were explored. The main results were as follows:(1) The climate drought intensity reflected by medium-short term fluctuations and the drought vulnerability reflected by trend item were extracted from the annual disaster series by using EEMD. (2) The peak difference of IMF-H indicated that the drought intensity in the three northeastern provinces were significantly higher than those of other provinces. (3) The linear relationship between IMF-H and climatic factors showed that summer climate anomalies had the highest contribution to disaster damage, especially the average daily sunshine hours and precipitation in July were selected as the key drought-influencing factors (KDII) in 10 provinces. (4) The time-series diagnosis results of KDII in various provinces showed that the risk of summer drought in the northern part of Yangtze River had increased since 2000. (5) At the time-lag of 0 to 12 months, the LAOI characterizing ENSO and atmospheric low-frequency oscillation in the northern hemisphere, such as Nino SST, Southern Oscillation and North Pacific teleconnection, had the significant impacts on the KDII in the study area. This study could provide scientific basis for regional drought monitoring and early warning.

Abstract:Topsoil restoration is a key step in the ecological restoration of the dump of open pit coal mine, and the thickness of soil cover directly affects plant growth and reclamation cost. In order to study the influence of the thickness of soil cover on soil water infiltration and plant water utilization in open pit mine dump, indoor soil column simulation test was adopted in this study. Five cover thicknesses of 10 cm, 20 cm, 30 cm, 40 cm and 50 cm were set up, and vertical infiltration test and indoor pot test (corn) were conducted, respectively. Combined with hydrogen and oxygen isotope stable tracing technology, soil infiltration and water use characteristics of corn with different cover thicknesses were studied to screen the optimal soil cover thickness for the waste dump in the region. The results showed that:the initial infiltration rate with a soil cover thickness of 10~30 cm (27.05~33.02 mm/min) was significantly higher than that with a soil cover thickness of 40~50 cm (21.59~24.89 mm/min) (p<0.05). The stable infiltration rate increased with the increasing of soil cover thickness. When the soil cover thickness was greater than 40 cm, the infiltration rate remained at about 3 mm/min with the increasing of the soil thickness. The infiltration process of gangue layer was greatly affected by the soil cover thickness. When the thickness of overlying soil was greater than 40 cm, the infiltration rate of gangue layer was basically stable at the infiltration rate of soil layer interface. The intersection between water hydrogen and oxygen isotope values of maize xylem and soil water hydrogen and oxygen isotope values with different soil thickness was mainly concentrated in the overlying soil layer. Therefore, the growth water of maize mainly came from the overlying soil layer. The greater the soil cover thickness was, the more intersection points of the two lines and the larger the distribution range of the intersection points, the larger the soil water utilization range of maize was. When the soil cover thickness was more than 40 cm, the water utilization range of maize was basically maintained within the range of 10~40 cm. Considering the maximum rainfall intensity of 190 mm/h in Fuxin city, the optimal reclamation thickness of open-pit dump in this area should be higher than 40 cm.

Abstract:Ecochemometrics is an effective method to study the balance of ecosystem and multiple chemical elements, and to clarify the impact of different fertilization systems on the carbon, nitrogen, phosphorus content and their ecostoichiometric ratio of plant-soil-microbial continuum, which can provide a feasible basis for revealing the nutrient cycle of ecosystem and realizing the element balance and sustainable development of mining reclamation agricultural system. In this study, the reclaimed land of the waste dump of Wujiata open-pit coal mine was taken as the research object, and six fertilization treatments were set up, including single application of organic fertilizer with three green manure ratios (A1B0, A2B0, A3B0) and microbial inoculum with different organic fertilizers (A1B1, A2B1, A3B1). The characteristics of carbon, nitrogen and phosphorus of plant-soil-microbial ecosystem were studied in combination with the planting of Sophora flavescens. The results showed that:(1) Compared with the single application of organic fertilizer, the combination of organic fertilizer and microbial inoculum had a significant effect on stem and leaf phosphorus, soil carbon, nitrogen, phosphorus and microbial biomass nitrogen (p<0.05), but had no significant effect on root nutrient. Among them, the combination of microbial inoculum and A1 organic fertilizer had the greatest impact on soil total phosphorus, increasing by 90.06%. Under the combination application of A2 organic fertilizer, the soil organic carbon and biomass nitrogen were affected most obviously, increasing by 104.60% and 71.95%, respectively. Under the combination application of A3 organic fertilizer, the total phosphorus in stem and leaf and soil total nitrogen were significantly affected. The total phosphorus in stem and leaf decreased by 183.96%, while soil total nitrogen increased by 29.14%. (2) Under the fertilization treatment, compared to the stem and leaf and microorganisms, the internal stability of S. flavescens root was weaker and more sensitive to exogenous nutrient inputs. (3) Under fertilization treatment, there was a strong coupling relationship between plant root nutrients and soil and soil microorganisms, so the nutrient balance of each component could be coordinated through root sensitivity to maintain plant stability.

Abstract:In order to study the effects of different application modes of biochar on water and salt regulation in saline alkali soil and wheat seedling growth, an indoor bucket planting simulation experiment was conducted. Biochar was covered on the surface of the soil in two forms of powdery and rod-shaped, with a mass percentage of 1%, 3% and 5%. Under the same treatment, biochar was mixed with 10 cm of the soil surface, and the treatment without biochar was used as a control (CK). The results showed that under the condition of "dry sowing and wet emergence", the emergence rate of wheat treated with FF (powdery cover) and GF (rod-shaped cover) was 7.33 to 9.00 and 3.00 to 3.33 times higher than that of CK, respectively. The emergence rate of FH and GH treatments increased by 66.67% to 166.67% and 33.00% to 367.00%, respectively, compared with CK. The plant height of FF and GF treatments significantly increased, with an increase of 21.52% to 34.55% and 24.54% to 40.48%, respectively, compared with CK. The plant height of FH and GH treatments increased slightly, with an increase of -1.35% to 12.22% and 3.76% to 8.59%, respectively, compared with CK. There were significant differences in post irrigation moisture content among different application modes, and FF treatment increased the surface soil moisture content by 0.31% to 15.58% compared with CK. The surface soil moisture content treated with GF decreased by 0.40% to 7.65% compared with CK. The soil moisture content of FH and GH treatments increased by 7.33% to 18.61% and 1.33% to 18.38%, respectively, compared with CK. After evaporation, the moisture content of FF and GF treatments increased by 4.34% to 45.38% and 27.08% to 53.22%, respectively, compared with CK. After evaporation, the moisture content of the 0-15 cm soil layer increased significantly. The soil moisture content of FH and GH treatments increased by 3.26% to 16.66% and 5.77% to 36.37%, respectively, compared with CK. The maximum relative change rate of conductivity in the 0-10 cm soil layer of CK was 124.76%, while that in FF and GF treatments was 59.61% to 114.73% and 18.21% to 86.47%, respectively. The relative change rate in conductivity of GH and FH treatments was 67.26% to 96.30% and 72.05% to 122.32%, respectively. Compared with CK, the evaporation of FF and GF treatments decreased by 0.76% to 27.21% and 53.49% to 77.02%, respectively. Compared with CK, the evaporation of FH and GH treatments decreased by 1.95% to 4.79% and 1.71% to 14.82%, respectively. The improvement effect of biochar depended on the amount and the application method of biochar. Under equal carbon input conditions, FF and GF treatments had better effects on water and salt distribution, inhibition of evaporation, and crop growth than FH and GH treatments, which could be used as suitable models for adding biochar to improve saline alkali land in arid areas.

Abstract:To understand the impact of more than 40 years of afforestation of Pinus sylvestris plantation on soil water and salt in the southern edge of Horqin sandy land, based on the soil and meteorological data of P. sylvestris forest land and grassland from March 2020 to November 2021 in Horqin sandy land, the double cumulative curve method (DCM) was used to verify the rationality of sample plot selection, the spatial instead of time method (STM) was used to study the variation pattern of soil water content and salinity in P. sylvestris forest land and grassland and the differences in their correlation with meteorological factors. P. sylvestris forest changed the distribution of water and salt in the longitudinal profile of the soil, both tended to be in a positive "S" shape. Forest effectively increased soil water storage (p<0.05), reduced soil salinity, and reduced the range of water sub active layer. The variability of forest soil water was higher (p<0.05), while the variability of salinity was lower (p>0.05). The correlation degree between the meteorological factors and soil moisture and salinity indicators in forest was different from that in grassland, weakening the correlation with rainfall and increasing the correlation coefficient with water vapor pressure deficit. These results indicated that P. sylvestris forest ecosystem had a strong function of water conservation and soil salinization inhibition.