Abstract:[Objective] The surface morphology changes and its relation with wind environment under wind regime disturbance by a solar photovoltaic array in a sandy area of the middle part of Kubuqi Desert, in order to provide a theoretical basis for determining a technical scheme to minimize wind and sand hazards at solar photovoltaic (PV) power stations.[Methods] Spatial distribution of surface erosion and deposition and characteristics of the surface morphology profile at five angles (0°, 45°, 90°, 135°, and 180°) between the solar PV array and the wind direction were analyzed by wind tunnel experiments.[Results] When the included angle between the solar PV array and the wind direction was ±90°, the surface erosion intensity was mainly moderate and severe, and deposition intensity was mainly mild. Surface erosion intensity was greatly reduced in the 3rd to 5th rows of panels because of sheltering effects. The erosion and deposition change law for all panel areas was similar at the ±45° angles. When the included angle was -45°, the surface erosion and deposition intensity were mainly mild and moderate. but severe deposition intensity occurred in a small area. When the included angle was -45°, the surface erosion intensity was mainly moderate and mild, and deposition intensity was mainly mild and moderate. The surface erosion and deposition intensity at the different included angles followed the order of 45°>90°>-45°>-90°>0°. As an example, when wind speed was 8 m/s, the surface erosion and deposition intensity were the smallest with the 0° angle, and the range of surface erosion and deposition was only 1.265 cm. The surface erosion and deposition intensity were the largest with the 45° angle, and the range of erosion and deposition reached 5.429 cm. In addition, when the absolute value of the included angle was equal and the sign was opposite, the wind and sand activity on the surface of the photovoltaic array was stronger when the included angle was positive than when it was negative. When the included angle was 45°, the surface erosion and deposition intensity was 1.566 times higher than that was -45°. When the included angle was 90°, the surface erosion and deposition intensity was 1.269 times higher than that was -90°.[Conclusion] The design of technical schemes to minimize wind and sand hazards at solar PV power stations in sandy areas should fully consider the prevailing wind direction conditions.

Abstract:[Objective] The rainfall characteristics and water and sediment control ability of different types of artificial forestland in an exposed feldspathic sandstone area were determined in order to provide guidance for vegetation construction in the study area and for sediment reduction into the Yellow River.[Methods] The annual natural rainfall and soil erosion of plots on Pinus tabulaeformis, Apricot, Hippophae rhamnoides, and Caragana korshinskii plantations, and on grassland and bare land were monitored by means of runoff plot monitoring.[Results] ① Under the condition of long duration heavy rain and moderate to heavy rain in an exposed feldspathic sandstone area, instantaneous rainfall presented a double peak trend, and cumulative rainfall increased in a ladder pattern. The short duration rainstorm and the instantaneous rainfall of a light to moderate rain showed a single peak trend, and the cumulative rainfall showed an S shape and a linear increasing trend, respectively. ② The erosion of exposed bedrock slopes was serious, with a total runoff of 28.48 L and a total soil erosion of 31.85 t/(hm²·a). The total runoff of vegetation slopes was between 9.8 and 18.41 L, and the total soil erosion was between 1.67 and 10.14 t/(hm²·g). There was no uniform rule for the yield and discharge for different types of artificial forestland with change in rainfall type. However, the amount of soil erosion followed the order of bare land > grassland > Caragana korshinskii > Apricot > Pinus tabulaeformis slightly > Hippophae rhamnoides forests. The yield and discharge of Pinus tabulaeformis forest and Hippophae rhamnoides forest were significantly correlated with soil erosion, with correlation coefficients of 0.929 and 0.893, respectively. The mean rainfall intensity and I₃₀ were significantly correlated with soil erosion, and the correlation coefficients were greater than 0.595. ③ The relationship between rainfall and erosion of different types of artificial forestland conformed to a multiple linear equation (R²>0.771). The Nse of the rainfall and runoff model was greater than 0.62. The Nse of the rainfall and sediment production model was greater higher than 0.57, except for the Caragana korshinskii plantation. It showed that the model accuracy was relatively high.[Conclusion] Under erosive rainfall conditions in a bare feldspathic sandstone area there is a certain functional relationship between rainfall, runoff, and sand production in forest plantation land, and the erosion on forest plantation land is smaller than on bare slope.

Abstract:[Objective] The effects of straw returning combined with reduced chemical fertilizer application on rice yield and nitrogen and phosphorus losses with runoff were studied in order to provide a scientific basis for the recycling and reuse of local agricultural resources and the prevention and control of agricultural non-point source pollution.[Methods] A three-year (2018-2020) field plot experiment was conducted that included two treatments:conventional fertilization (T₁), and straw returning + conventional fertilization reduced by 28.57% for nitrogen and 25.11% for phosphorous (T₂). The concentrations and losses of nitrogen and phosphorus in farmland surface runoff, yield, nitrogen and phosphorus uptake by rice straw and grain, and soil nutrients at harvest were determined.[Results] As the number of straw returning years increased, T₂ achieved a significant increase in yield. Compared with T₁, the yield of T₂ increased by 16.93% in 2020. Compared with T₁, the loss of the total nitrogen and NO^-₃-N for T₂ increased by 6.25%~14.97% and 6.99%~15.03%, respectively. The loss of the soluble total nitrogen, the total phosphorus, and the soluble total phosphorus for T₂ was 0.94%~6.03%, 4.66%~10.32%. and 5.77%~21.15%, respectively, lower than observed for T₁. The interannual changes of total phosphorus, available phosphorus, nitrate nitrogen, and ammonium nitrogen in soil were significant (p<0.05). Compared with T₁, T₂ significantly reduced soil total phosphorus by 8.79% and available phosphorus by 30.56%.[Conclusion] Continuous straw returning combined with reduced chemical fertilizer application ensured the crop yield and reduced the input of chemical fertilizer and the loss of phosphorus in farmland runoff, but increased the risk of nitrogen runoff loss. Therefore, the continuous straw-returning system should be further optimized in actual agricultural production.

Abstract:[Objective] The effects of water storage irrigation and seasonal freezing and thawing on soil respiration were determined in order to improve the utilization efficiency of irrigation water resources, and save irrigation water resources at Shiyang River watershed of Gansu Province in extremely arid regions in China.[Methods] The LI-8100 automatic soil carbon flux measurement system was used to observe and analyze soil respiration rates. Treatments were divided into irrigation and non-irrigated treatments according to the low irrigation quota of 1 199.4 m³/hm². The freeze-thaw cycle was divided into three time periods:freezing period, freeze-thaw period, and thawing period.[Results] Under the effects of seasonal freeze-thaw cycles, soil respiration rate and soil carbon emissions of farmland ecosystems increased and the carbon cycle of farmland ecosystems was changed, resulting in increased crop growth and food production. Soil respiration rates responded differently to moisture and temperature under different land use patterns. During the entire process, soil respiration rate was greater during the thawing period than that of the freezing period and the freeze-thaw period. The soil CO₂ in the three periods of freezing, freeze-thaw, and thawing were all shown to be sources, but were all converted from sources to sinks at very low night temperature.[Conclusion] Water storage irrigation regulated the process of soil respiration throughout the freezing and thawing period and changed the carbon cycle of farmland ecosystems in extremely arid regions. Under the superimposed action of moisture and seasonal freeze-thaw, the soil respiration rate of storage irrigation plots fluctuated more drastically with temperature than the soil respiration rate of non-storage plots, and this result was consistent with the change trend of temperature, indicating that moisture aggravates soil respiration fluctuations with temperature.

Abstract:[Objective] The effects of different rainfall characteristics and different underlying surface conditions on soil erosion and sediment yield were determined in a low mountain and hilly area of Lianyungang City, Jiangsu Province, in order to provide a reference for local soil and water loss prevention and improvement of soil and water conservation benefits.[Methods] Local erosive rainfall types from the Heilin soil and water conservation monitoring point from 2013 to 2020 were classified by the K-means clustering method. The characteristics of erosive rainfall were identified and the correlations among rainfall, runoff, and sediment yield of five slope runoff plots at the monitoring point were analyzed by the grey correlation method. Differences in runoff and sediment yield capacity due to different underlying surface conditions were compared by the double accumulation curve method, and the soil and water conservation effects of human activities on surface disturbance were analyzed.[Results] ① Erosive rainfall mainly occurred during the flood season, mainly from type Ⅰ (small rainfall and light rainfall intensity) rainfall events, accounting for 66% of the rainfall frequency, followed by type Ⅱ (medium rainfall and medium rainfall intensity) rainfall events and type Ⅳ (large rainfall and medium rainfall intensity) rainfall events. Type Ⅲ (large rainfall and heavy rainfall intensity) rainfall events were the least frequent type of rainfall events; ② Sediment yield was closely related to rainfall and runoff depth, and the correlation coefficient ranges were 0.64~0.85 and 0.61~0.86. respectively; ③ The runoff and sediment yield of secondary rainfall caused by type Ⅲ rainfall were the largest, and the total amount of soil loss caused by type Ⅳ rainfall was the largest; ④ The sediment yield capacity of agricultural land was the largest, followed by forest land. The sediment yield capacity of natural wasteland was the smallest. Reducing the artificial disturbance of surface soil, horizontal ridging and planting, and selecting plants with high coverage were more conducive to improving local soil and water conservation benefits. On the whole, the soil and water conservation benefits of forest land were greater than those of agricultural land. ⑤ The differences in runoff and sediment yield due to different underlying surfaces decreased gradually with increasing rainfall and rainfall intensity.[Conclusion] Erosive rainfall mainly occurred during the flood season in a low mountain and hilly area of Lianyungang City. There were obvious differences in the characteristics of runoff and sediment yield due to different rainfall types and underlying surfaces, and the benefits of forest land to soil and water conservation were greater than those of agricultural land.

Abstract:[Objective] The response of the pioneer tree species Pinus massoniana to drought and subsequent recovery in the erosion zone of Changting County, Fujian Province was determined in order to provide scientific support for the recovery and reconstruction of vegetation in this zone.[Methods] A 30 m×30 m population-monitoring sample area was selected in a severely degraded site in Hetian Town, Changting County. The basal diameter, tree height, and reproduction of each P. massoniana tree within the sample area were measured. The life rate changes for P. massoniana during 2016-2020 were calculated with the help of a survival growth function and a reproduction function, and analyzed and discussed with regard to the annual standardized precipitation evapotranspiraton index (SPEI) calculated for the same period.[Results] ① When drought occurred in the erosion area of Changting County, the response of each life rate for P. massoniana was obvious. Individual tree growth and survival rate decreased. At this time, the reproductive diameter class advanced, the probability of reproduction of small-sized trees increased. P. massoniana adjusted responses to maintain the existence of the population; ② After the erosion area entered the recovery period, the growth of small-sized trees increased, survival rate gradually increased, and the probability of reproduction first increased and then decreased. Each life rate of large-sized trees gradually rebounded, and the recovery rate was relatively fast. However, all individual trees did not recover to the state that existed before the drought occurred.[Conclusion] Severely degraded populations of P. massoniana has responded to drought to a high degree, and each life rate (survival, growth, and reproduction) changes rapidly, but the recovery ability of the tree population is poor.

Abstract:[Objective] The canopy interception ability of different types of garden plant communities was determined in order to provide a theoretical basis for selecting the plant community with the best canopy interception effect.[Methods] We selected seven plant communities with different structures, and measured actual throughfall and stem flow. We used the water balance method to obtain canopy interception.[Results] The greatest canopy interception rate (49.86%) was observed for a single-layer coniferous and broad-leaved mixed forest. The lowest interception rate (23.66%) was observed for a single-layer broad-leaved shrub canopy. The throughfall, stem flow, and the canopy interception were linearly and positively correlated with rainfall amount (R² of about 0.9). Leaf area index, canopy closure, canopy thickness, green coverage area, and three-dimensional green quantity were negatively correlated with penetration rate, and positively correlated with interception rate.[Conclusion] The canopy of a garden plant community has the ability to retain rainwater, and different types of communities have different abilities. The interception rate of the single-layer broadleaved shrub canopy was the lowest, and that of the single-layer coniferous and broadleaved mixed forest was the greatest. Greater leaf area index and canopy density, thicker canopy, larger green cover area and three-dimensional green quantity all lead to greater canopy interception capacity of a garden plant community.

Abstract:[Objective] In order to understand the water use strategy of Ailanthus altissima and to formulate efficient water management measures for A. altissima, we investigated the characteristics of sap flow and radial stem variation of A. altissima under four volumetric soil moisture content treatments[10%~15% (W₁), 15%~20% (W₂), 20%~25% (W₃), and 25%~30% (W₄)] and their relationships with meteorological factors.[Methods] Thermal diffusion probes (TDP) were used to continuously observe sap flow, and radial stem change recorders were used to monitor changes in stem diameter of A. altissima. Changes in related environmental factors were simultaneously monitored.[Results] Sap flow was almost the same, and growth rate and variation of stem diameter were similar for the W₃ and W₄ treatments. Sap flow increased with increasing soil moisture in the range of W₁ to W₃, whereas the proportion of nighttime sap flow to total daily sap flow showed the opposite trend[W₁ (12.3%)>W₂ (11.9%)>W₃ (6.0%)]. Variations in the stem diameter of A. altissima at the daily scale decreased with increasing soil moisture, but the growth rate increased accordingly. The correlation between sap flow and meteorological factors increased with increasing soil moisture content during the daytime, but decreased at night. Changes in both sap flow and stem diameter lagged behind solar radiation and ahead of vapor pressure deficit (VPD), and the time lag between these two indicators and VPD decreased with increasing soil moisture, while the time lag between both and solar radiation was little affected. Changes in sap flow and stem diameter of A. altissima at the daily scale showed an inverse change pattern, and the changes in sap flow always preceded the changes in stem diameter, and the time lag shortened as soil moisture increased.[Conclusion] Changes in sap flow and stem diameter of A. altissima to soil moisture changes were closely related. The soil moisture threshold value at which A. altissima could fully utilize soil moisture was the W₃ level. Therefore, the W₃ soil moisture treatment is the most suitable irrigation threshold for A. altissima.

Abstract:[Objective] The effects of different grazing intensity on vegetation features, soil physical properties, and soil erosion in a steppe desert were determined in order to provide a scientific basis for soil erosion control, degradation and ecosystem restoration in this region.[Methods] The vegetation community, soil physical properties, and soil erosion processes of sample plots under four different grazing intensities (heavy, moderate, light, and no grazing) were studied in the Xilamuren desert steppe of the Inner Mongolia Autonomous Region by use of in-situ monitoring and simulation experiments.[Results] ① Average coverage, height, and aboveground biomass of the vegetation community decreased as grazing intensity increased, while species richness index, diversity index, and evenness index increased. ② Sand content of the soil increased with grazing intensity, and bulk density and infiltration of the surface soil (0-10 cm) were more affected by grazing. ③ Under the same rainfall intensity, soil erosion and sediment yield increased with increasing grazing intensity. Soil primary infiltration rate, Simpson dominance index, and sand content in the soil were the key factors affecting soil erosion features under different grazing intensity.[Conclusion] Grazing significantly influenced the desert steppe vegetation community characteristics and soil hydro-physical properties. Therefore, grazing intensity should be controlled to moderate intensity (i.e., two sheep units/hm²) or below. For steppe regions damaged by heavy grazing, soil erosion resistance can also be increased by soil improvement through the use of appropriate artificial reseeding and introduction of microorganisms.

Abstract:[Objective] The spatial-temporal variations of soil water erosion before and after the Wenchuan earthquake in the Baisha River basin of Dujiangyan City, Sichuan Province were assessed to support water source protection efforts and comprehensive control of soil erosion in the earthquake-stricken area.[Methods] The characteristics of soil water erosion (i. e., area, intensity, and spatial distribution) in the Baisha River basin from 2007 to 2020 were quantitatively analyzed by using the Chinese Soil Loss Equation (CSLE).[Results] ① The intensity of soil water erosion after the Wenchuan earthquake in the Baisha River basin initially increased and then decreased. The average soil erosion modulus values for the Baisha River asin were 817.51, 3 000.11, 5 828.89, 1 549.76, and 1 558.37 t/(km²·a) in 2007, 2008, 2013, 2018, and 2020, respectively. The intensity of soil erosion in 2020 was mainly classified as light erosion, and the average soil erosion modulus was 48.1% lower than in 2008. ② The average soil erosion modulus gradually increased with increasing slope gradient or altitude. Soil erosion amount contributed by regions with slope greater than 35° and elevation above 2 000 m accounted for 85.44% and 68.20%, respectively, of the total erosion amount in 2020. In addition, the extremely severe erosion area with an average soil erosion modulus of more than 5 000 t/(km²·a) mainly occurred in areas with elevation above 4 000 m. ③ Although the average vegetation coverage in the Baisha River basin in the past 10 years was between 60% and 74%, the proportion of the area classified as having moderate and more severe erosion was still greater than before the earthquake. In 2020, the proportion of moderate and more severe erosion area was 4.13 times greater than in 2007.[Conclusion] Even though the soil water erosion situation has effectively improved between 2013 and 2020, areas of intense and more severe erosion remain in the middle and upper reaches of the study area, and the topographic conditions and rainfall erosivity had an obvious impact on the change in erosion area.

Abstract:[Objective] The contents of C, N, P, and their ecological stoichiometry characteristic contained in foliage, branches, litter, and soil of different age grades of Populus alba L. var pyramidalis stands were determined in order to provide a theoretical basis for the sustainable development of farmland shelterbelts in the Alar Reclamation Area, South of Xinjiang Wei Autonomous Region.[Results] The contents of C, N, P, and stoichiometric characteristics were:① C content followed the order of litter (395.14 g/kg)>foliage (365.29 g/kg)>branch (363.84 g/kg)>soil (9.47 g/kg); N content followed the order of foliage (13.37 g/kg)>litter (9.10 g/kg)>branch (7.31 g/kg)>soil (0.72 g/kg); P content followed the order of foliage (0.46 g/kg)>branch (0.43 g/kg)>soil (0.37 g/kg)>litter (0.27 g/kg). ② Compared with the national average value, foliage-branch-litter-soil showed a pattern of low C, low N, low P. The total C content showed a trend of "increasing-decreasing-increasing" with the age grades. The total content of N in the four age-grades showed a trend of decreasing with increasing soil depth except for the third age grades. The total contents of P generally increased with increasing age grades, and were significant between different age grades in the same soil layer (p<0.05). ③ The soil C:N ratio (13.05) was higher than C:N (11.9) in China. The C:P and N:P ratios (24.04, 1.83) were lower than those of soil C:P and N:P ratios (60.0, 5.20) in China. ④ Soil N and P contents in the 0-80 cm soil layer of Populus alba L. var pyramidalis were significantly negatively correlated with foliar N content (p<0.01), and positively correlated with foliar P content (p<0.01). Litter N content was significantly positively correlated with surface soil N content (p<0.01). There was a significant negative correlation between litter P content and 20-40 cm soil P content (p<0.01).[Conclusion] N and P contents are the limiting factors for the growth of Populus alba L. var pyramidalis shelterbelts because of lack of management and protection in the Alar Reclamation Area. Therefore, N and P must be added appropriately by artificial measures so as to improve soil fertility and the quality of farmland shelterbelt stands.

Abstract:[Objective] The differences in water infiltration characteristics between different land use types in Horqin sandy land were determined in order to provide a scientific reference for the study of water and material transport in the vadose zone in arid and semi-arid regions.[Methods] Soil infiltration and its influencing factors for eight typical land use types (Pinus sylvestris plantation, Caragana korshinsk plantation, Caragana microphylla plantation, abandoned grassland, meadow grassland, sparse forest grassland, corn field, and bare sandy land) in Horqin sandy land were measured in the field using a double ring infiltration apparatus and a laboratory analysis of soil physical properties. At the same time, the Kastiakov model, the Horton model, the Philip model, and the G-P comprehensive model were used to simulate the water infiltration process, and goodness of fit values for the models were compared.[Results] ① There were significant differences in soil infiltration characteristics among different land use types. The initial infiltration rates ranged from 1.595 mm/min to 12.020 mm/min, and followed the order of bare sandy land>Caragana korshinskii plantation>corn field > Pinus sylvestris plantation>Caragana microphylla plantation>meadow grassland>abandoned grassland>sparse forest grassland. The infiltration rate at 15 min varied from 0.617 mm/min to 3.690 mm/min, and followed the order of bare sandy land>Caragana korshinskii plantation>Pinus sylvestris plantation>Caragana microphylla plantation>corn field>abandoned grassland>meadow grassland>sparse forest grassland. The saturated infiltration rate varied from 0.576 mm/min to 3.495 mm/min, and followed the order of bare sandy land>Caragana korshinskii plantation>corn field>Caragana microphylla plantation>Pinus sylvestris plantation>abandoned grassland>meadow grassland>sparse forest grassland. ② The infiltration rate of different land use types was negatively correlated with soil bulk density and fine sand content, and positively correlated with medium sand content. Stable infiltration rate was positively correlated with non-capillary porosity. ③ The goodness of fit values for the models to estimate soil infiltration in Horqin sandy land followed the order of Horton model>G-P comprehensive model>Kastiakov model>Philip model. The Horton model had the highest coefficient of determination and the smallest relative error, and could accurately reflect the actual situation of soil infiltration in Horqin sandy land.[Conclusion] The characteristics of soil infiltration were different among different land use types in Horqin sandy land. The Horton model had high fitting ability in Horqin sandy land, and can, therefore, be used to estimate water infiltration.

Abstract:[Objective] The effects of bio-based composite amendments on the physicochemical properties and microbiota of saline soils in the Yellow River delta and the Northern Jiangsu mudflats were determined in order to provide a scientific reference for the improvement and utilization of saline soils in the region and for the ecological agro-pastoralism.[Methods] A pot experiment with alfalfa was conducted to study the influence of the application of compound biomaterials on the physico-chemical properties and microbial flora of coastal saline soils from the Yellow River delta (S) and the northern Jiangsu mudflats(J). The compound biomaterials consisted of vermicompost, active enzyme conditioners, and endophytic mycorrhizal inoculants. The experiment consisted of four treatments:the Yellow River delta soil with (SE) and without (SC) compound amendments, and the Northern Jiangsu tidal flat soil with (JE) and without (JC) compound amendments.[Results] Soil organic matter during the alfalfa branching stage increased by 45.30% and 32.45% in the SE and JE treatments, respectively, compared with the control treatment, and available potassium increased by 41.00% and 39.92%, respectively. Total dissolved salt in the soil during the alfalfa budding stage decreased by 14.10% and 27.85% in the SE and JE treatments, respectively, compared with the control treatment, and soil organic matter increased by 51.99% and 73.59%, respectively. Additionally, the diversity index of the soil microbial community during the budding stage was significantly increased compared with the control treatment, The dominant bacterial phyla were Proteobacteria, Bacteroidetes, Acidobacteria, Planctomycetes, and Actinobacteria. The total dissolved salt and available potassium in the soil were the main driving factors changing soil microbial community structure.[Conclusion] The bio-based compound amendments could effectively reduce the total dissolved salt in soil, increase soil available nutrients, and increase soil microbial flora, and thereby significantly improve overall soil fertility.

Abstract:[Objective] The effects of mixed additions of a water-retaining agent and bacterial agents on soil characteristics were determined in order to provide a theoretical basis for promoting mine vegetation restoration.[Methods] Different concentrations of a water-retaining agent and mineral-solubilizing microbial agents were added to the potted soil of Robinia pseudoacacia. The concentrations of the water-retaining agent were:B₁ (0%), B₂ (0.3%), and B₃ (0.5%). The microbial-agent treatments were J₀ (without added microorganisms), J₁[adding NL₁₁(Bacillus thuringiensis)], J₂[adding NL₁₁ + NL₁₁(Streptomyces thermocarboxydus)], J₃[adding NL₁₁+NL₁+NL₁₅(Gongronella butleri)]. The effects of mixed additions of the water-retaining agent and microorganisms on R. pseudoacacia were determined by analyzing the growth, soil nutrients, soil organic carbon, and soil enzyme activity of R. pseudoacacia.[Results] ① The addition of microbial strains increased soil nutrient content and soil enzyme activity. The J₂ microorganism treatment performed the best. ② Readily available soil nutrients initially increased and then decreased with increasing concentration of the water-retaining agent. The greatest effect on soil nutrient and enzyme activity was observed for the 0.3% water-retaining agent concentration. ③ The combinations of J₂B₁, J₃B₀, and J₂B₂ had the greatest effect on increasing soil nutrients and enzyme activities.[Conclusion] The addition of soil microbial agents and a water-retaining agent to the soil increased soil nutrients and enzyme activities. The combinations of J₂B₁, J₃B₀, and J₂B₂ had the greatest effect.

Abstract:[Objective] The spatio-temporal characteristics of the eutrophication status in Baoan Lake, and the key water environmental impact factors were studied in order to provide a basis for ecological restoration and protection.[Methods] Monitoring sites were set up in Baoan Lake. Sampling and monitoring were conducted from 2019 to 2021. The trophic state index (TLI) was introduced to evaluate the nutritional status of the lake, and spatial autocorrelation analysis was used to study the spatial correlation and aggregation degree of eutrophication in Baoan Lake. The main water environmental impact factors of chlorophyll a concentration were analyzed by a logit model.[Results] The nutrient status of Baoan Lake fluctuated between mesotrophic and slightly eutrophic, and the range of TLI was 47.25~55.86. The eutrophication level of Baoan Lake showed significant spatial autocorrelation, with Global Moran's I values of 0.46, 0.93, 0.60, 0.31, 0.60, and 0.62. The southern areas of the main boady of Baoan Lake were the hot spots (high/high concentration) for lake eutrophication level (p<0.01), and Biandantang lake area was the cold spot (low/low concentration) for lake eutrophication level (p<0.01). The main water environmental factors affecting the change of chlorophyll a concentration were transparency > TP > pH value > COD_Mn > water depth > DO, which were significantly correlated with chlorophyll a concentration.[Conclusion] The eutrophication status of Baoan Lake water is good. Further improvement in the water nutritional status of Baoan Lake can be achieved by controlling the agricultural non-point source pollution, strengthening the management of rivers, regulating water level, recovering aquatic vegetation, and so on.

Abstract:[Objective] The application of ultrasonic chain pin sensor in soil wind erosion was studied by experiment to verify the monitoring accuracy and reliability of the equipment for wind erosion in order to provides a theoretical basis for the improvement and popularization of the equipment.[Methods] A wind erosion test using the ultrasonic chain pin sensor was conducted in a wind tunnel.[Results] The measurement error of the ultrasonic chain pin sensor in the wind tunnel erosion test was ±1 mm, and the measurement accuracy was very high. Measurement error changed little as wind erosion thickness increased, and the variance was only 0.04 and exhibited high stability.[Conclusion] The ultrasonic chain pin sensor had good accuracy, stability, and reliability in wind erosion monitoring, and can be used for automatic monitoring of wind erosion.

Abstract:[Objective] The variation characteristics of sediment transport for different specifications of gauze sand barriers in spring, summer and autumn were obserred continuously in order to provide a scientific basis for further evaluation of the sand-fixing effect of gauze sand barriers.[Methods] Field positioning and regular observation methods were used to determine the amount of sediment transport for gauze sand barriers in different seasons in the Ulanbuh Desert.[Results] The 2 m×2 m, 3 m×3 m, 3 m×4 m, and 4 m×4 m gauze sand barriers were set to intercept wind and sand flow, and the effects increased as grid-spacing became smaller. Sediment load changed with height above the soil surface in an exponential relationship in all three seasons. The amount of sediment transported by the northwest wind was more than the amount transported by the southeast wind. The amount of sediment transported in spring was more than the amount transported in summer and autumn. Compared with the control, the net sediment transport intercepted in the 0-60 cm height range was reduced 85.98% by the 3 m×4 m gauze sand barrier in spring, and the net sediment transport in this height range was reduced 79.56% in summer and autumn.[Conclusion] Sediment transport of the gauze sand barrier was mainly concentrated in the 20 cm height range above the ground surface. As the size of the gauze sand barrier increased, its ability to reduce the amount of sediment transport decreased. Gauze sand barriers can be set to effectively reduce the hazards of wind-sand flows.

Abstract:[Objective] In view of the sand burying problem caused by the wind and sand flow on the highway in Bashang area of Zhangjiakou City, Hebei Province, a comprehensive wind and sand fixing system of sand retaining dike sand fixing brick was established, and its wind and sand fixing effect was analyzed, in order to provide relevant technical parameters for the prevention and control of wind and sand disasters on the highway.[Methods] The flow field change around the sand retaining dike, and sand particle movement trajectory, sand-fixing brick spacing, and sand accumulation around the sand-fixing brick were numerically simulated by ANSYS software to evaluate the wind-prevention and sand-fixation effects of the integrated sand-retaining dike and sand-fixing brick system.[Results] ① A deceleration zone, an acceleration zone, a turbulence zone, and a recovery zone were formed around the sand-retaining dike as wind and sand passed through it. The sand-retaining dike with a slope ratio of 1:1.2 had the most effect on slowing wind and fixing sand. ② A discrete phase model (DPM) was used to simulate the trajectory of sand jumping on the sand-retaining dike. When the wind speed is 12~20 m/s, the sand falling point was 11~21 m away from the sand-retaining dike, and then the relative position of laying the sand-fixing brick was determined. ③ When the starting position of sand-fixing bricks was 11 m away from the sand-retaining embankment, and they were laid in 11 rows in a square form of 1 m×1 m, then the effect of fixing surface quicksand was the best.[Conclusion] The integrated sand-retaining dike and sand-fixing brick system reduced the wind speed and blocked the surface quicksand by "far-resistance and near-fixation". The sand-fixing brick barrier can effectively prevent the restart of sand particles crossing the sand retaining dike, thereby decreasing the occurrence of highway sand burial, and ensuring driving safety in wind and sand disaster areas.

Abstract:[Objective] The data that could provide a reference basis for the application of an anchor-reinforced vegetation system (ARVS) were obtained to protect newly excavated slopes with expansive soil.[Methods] Field tests were conducted on a newly excavated bare slope, vegetated slope, and ARVS-protected slope of expansive soil in Nanning City. Soil moisture content, soil temperature, and anchor shaft force of the slope were monitored to study the depth of atmospheric influence of ARVS on a newly excavated expansive soil slope under atmospheric action.[Results] The depth of atmospheric influence on the bare slope developed the fastest, developing to about 2.4 m in a short time. The depth of atmospheric influence on the ARVS-protected slope developed the slowest. The depth of atmospheric influence was less than 1.8 m after repeated rainfall events. ARVS restrained the expansive effect and limited the development of expansive and shrinking fissures, together with vegetation and high performance turf reinforcement mats (HPTRM), ARVS slowed down the development of the depth of atmospheric influence to the interior. As the depth of atmospheric influence developed to the deep part of the soil body, the neutral point moved deeper.[Conclusion] The vegetation, HPTRM, and anchor rod of ARVS interacted with each other to limit the development of atmospheric influence depth on a newly excavated expansive soil slope by restraining the expansive effect.

Abstract:[Objective] The water quality of four monitoring sections of the main stream of the Beiluo River from 2014 to 2020 were evaluated and analyzed in order to provide a basis for further improving the water environment of the river basin.[Methods] The main pollution indicators of the Beiluo River were screened and evaluated using principal component analysis and a comprehensive water quality identification index method according to the law of intra-annual distribution of water volume in the Beiluo River. A given year was divided into the wet season, the flat water season, and the dry season.[Results] Chemical oxygen demand, ammonia nitrogen, and fluoride were the most significant indicators affecting the water quality of the Beiluo River. From the distribution along the course of the river, the water quality in middle reaches of the main stream of Beiluo River was the best, followed by the upper reaches. The water quality in the lower reaches was relatively poor. The water quality in the main stream of the Beiluo River improved significantly after 2018, basically meeting the requirements of water functional area Ⅲ water quality.[Conclusion] The main source of pollution in the upstream and midstream sections of Beiluo River came from the discharge of domestic sewage and livestock breeding wastewater from coastal towns. Industrial wastewater from the coal chemical industry and other enterprises in the downstream section of the river and agricultural surface source pollution caused by nitrogen fertilizer application were the main factors affecting the water quality of the river.

Abstract:[Objective] The status of ecological security in mining cities was determined and the factors restricting the development of ecological security were clarified in order to provide a scientific basis for sustainable mining in Anhui Province.[Methods] A comprehensive evaluation index system based on economy-environment-society was constructed for soil and water ecological security of nine mining cities in Anhui Province. The multiplicative normalization method was used to combine the optimized G1 and CRITIC weighting methods to achieve subjective and objective weight assignment. Then, the VIKOR model was used to consider the group effect and individual compromise based on compromise programming, and the difference of measured values of different weight indexes was taken into account. Finally, an obstacle degree model was used to diagnose the obstacle factors.[Results] The G1-CRITIC-VIKOR model under the interaction of multiple indicators produced results that were well matched with the actual data. The nine mining cities in Anhui Province were ranked (from high to low) based on their soil and water ecological security levels as Chizhou, Xuancheng, Chuzhou, Tongling, Ma'anshan, Suzhou, Bozhou, Huaibei, and Huainan. The proportion of workers and peasants employed, the matching coefficient of water and soil resources, the per capita water consumption, the proportion of land reclamation, and the per capita disposable income were the key factors restricting the level of water and soil ecological security of mining cities in Anhui Province.[Conclusion] The mining cities in Anhui Province should actively carry out ecological civilization construction and strive to transform their economies into intensive economies. At the same time, afforestation efforts should be implemented for ecological restoration and reconstruction of damaged mining areas so as to ensure the scientific and reasonable mining of coal resources on the basis of ecological security of water and soil.

Abstract:[Objective] The method for quickly and accurately measuring sediment concentrations in water samples in the field based on differential pressure was studied.[Methods] Four soil types (including Lou soil, sandy soil, saline-alkali soil, and paddy soil) were chosen to prepare 11 water samples with different sediment concentrations based on the principle of pressure difference. The pressure difference between a water sample and the atmosphere was determined by using digital differential pressure meter (abbreviated as pressure difference) in order to establish the relationship between sediment concentration and pressure difference.[Results] Sediment concentration and pressure difference were linearly and positively correlated (significant at p=0.01). The method of pressure difference combined with a theoretical formula to determine sediment concentration was feasible for three of the water samples (including the Lou soil water sample, the sandy soil water sample, and the paddy soil water sample), and the absolute value of the maximum relative error was less than 15%. However, the method was not suitable for the sandy soil water sample. The absolute value of the maximum relative error in the determination of sediment concentration for the sandy soil water sample was as high as 39%. Therefore, to reduce the error, a correction equation was established by determining the pressure difference between pure water and water samples with sediment content of 500 kg/m³, and then combined with the measured pressure difference to calculate the sediment concentration. The absolute value of the maximum relative error was found to be less than 8%.[Conclusion] This method can accurately determine the sediment concentrations of water samples. It could provide a new way for conveniently determining sediment concentration in the field for soil and water conservation monitoring.

Abstract:[Objective] The spatial optimization of land resources in the Kashgar area was studied to provide theoretical support for sustainable development of the society and economy of the area.[Methods] Food security, economic benefits, and ecological benefits (carbon sequestration, water production, and soil erosion) were set as the multi-objective functions of the algorithm, and the NSGA-Ⅱ algorithm was used to obtain a reasonable optimization of the land use quantity structure. Then the GeoSOS-FLUS model was used to simulate the spatial optimization of land use according to the optimization results of quantitative structure, natural conditions and economic factors. Finally, the spatial optimization of the Kashgar area was analyzed using Fragstats 4 software for landscape pattern analysis.[Results] ① GDP, carbon sequestration, and grain production were all higher under the three optimization strategies than before optimization, and soil erosion was reduced. Water production was only increased when ecological benefits were prioritized. ② From 2005 to 2020, arable land and construction land increased to different degrees. Watershed, forest land, and unused land decreased to different degrees. ③ The optimization results for land use pattern under the economic priority, the ecological priority, and ecological-economic coordinated development, and land use data in 2020 were analyzed by Fragstats 4. Compared with the results obtained prior to optimization, Shannon diversity and dispersion and juxtaposition indices increased under all three optimization strategies, and patch cohesion and habitat diversity also increased.[Conclusion] The six land use types were distributed in the landscape in a balanced manner, and the land use type of grassland transition was increased. The optimized land resources can better meet the ecological sustainable development goals, and their layout was more reasonable, providing auxiliary decision-making services for the future allocation of land resources in Kashgar area.

Abstract:[Objective] Differences in above ground biomass (AGB) estimation based on remote sensing images with different spatial resolutions were analyzed, and a basis for the selection of different spatial resolution images for remote sensing estimation of AGB in desert ecosystems was provided.[Methods] Based on a ground-based AGB survey, the AGB-MSAVI statistical model was established by combining Landsat 8 and Sentinel-2 images to estimate AGB in a feldspathic sandstone area by remote sensing, and to analyze the differences between the two estimates in different vegetation coverage areas (high, medium, and low).[Results] Both Landsat 8 and Sentinel-2 images could estimate AGB well, and the spatial distributions of AGB estimation results were consistent. The mean relative errors for the AGB estimation models based on Landsat 8 and Sentinel-2 data were 13.41% and 11.42%, respectively, and the accuracy of AGB estimation based on Sentinel-2 data was relatively higher. There were some differences in AGB estimated by Sentinel-2 and Landsat 8 data in different vegetation coverage areas.[Conclusion] In the low and high vegetation coverage areas, the differences between AGB estimated by Sentinel-2 and Landsat 8 data were relatively small. In contrast, in the medium vegetation coverage area, the spatial heterogeneity was relatively significant, the remote sensing data were constrained by the spatial resolution, and the differences between AGB estimated by the two images were relatively large. The high spatial resolution remote sensing images were effective for improving AGB estimation accuracy.

Abstract:[Objective] The a curing test of industrial waste iron tailings sand and loess mixed soil by adding an ionic curing agent or a glutinous rice slurry was conducted, and the curing effects of the two curing agents on the target soil sample were compared in order to provide theoretical support for subsequent engineering application and research.[Methods] An ionic curing agent and a glutinous rice paste were used to solidify the target mixed soil. The influence of the two curing agents on the strength and durability of the soil specimen was comprehensively evaluated through changes in the compressive strength of the soil specimen through dry-wet, freeze-thaw cycles and natural weathering tests. The influence of pore structure on compressive strength was measured using a scanning electron microscope and a specific surface area test.[Results] The strength increasing effect of mixed soil with a 1.5% ionic curing agent was better than that of other ionic curing agents, and was 50% greater than that of untreated soil. The strength increasing effect of soil mixed with 10% glutinous rice pulp was greater than observed for other rates of glutinous rice pulp mixed with soil, and the strength of the treated soil increased by 110%. After the durability test, the strength loss rate of soil mixed with the 1.5% ionic curing agent was smaller, and the residual strength of soil mixed with 10% glutinous rice pulp was greater.[Conclusion] Both the ionic curing agent and the glutinous rice pulp treatments can increase the strength performance of soil materials. Glutinous rice paste could be better curing agent than the ionic curing agent.

Abstract:[Objective] The causes of waterlogging in Zhengzhou City were studied in order to provide a reference for risk prevention and operation management of rainstorm waterlogging disasters in important parts of the urban infrastructure.[Methods] The SCS-CN hydrological model was used with meteorological data from 2016 to 2020, and with soil, slope, and land use data in 2020 to calculate the underlying surface runoff in Zhengzhou City and to study the relationship between slope, soil, land use and runoff.[Results] ① The distribution of surface runoff in Zhengzhou City from 2016 to 2020 showed patterns of "high in the northeast, low in the southwest" and "high in urban areas and low in mountainous areas". Runoff was mainly located in areas with more intensive human activities, except for water areas. ② Runoff was greatest on the gentle slopes. Slope contribution rate was positively correlated with area. ③ The soil in Zhengzhou City was divided into four categories:A (coastal aeolian sandy soil), B (loess soil), C (fluvo-aquic soil, etc.), and D (cinnamon soil). The runoff of category D soil was the largest, and the four categories of soil all exhibited a gradual upward trend in runoff. There was a positive correlation between soil contribution rate and area. Zhengzhou City has primarily category C (fluvo-aquic) soil with low infiltration rate. ④ The SCS model showed that drier soil in the early stage leads to greater rainfall infiltration and less runoff. The larger the CN value, the smaller the S value (potential maximum retention or infiltration), and the larger the runoff.[Conclusion] Surface runoff in Zhengzhou City was more concentrated in the northeast construction area. Greater runoff was more likely to cause waterlogging. Sponge bricks and green belts should be added to areas where runoff is concentrated, and drainage pipes should be repaired in a timely manner. Development of southeastern Zhengzhou City should be promoted to alleviate the impact of human activities on surface runoff in Northeastern Zhengzhou City.

Abstract:[Objective] The spatio-temporal evolution characteristics and its reasons of eco-environmental vulnerability in the Pearl River delta were studied in order to provide theoretical basis for regional development.[Methods] The pressure-sensitivity-restoration (PSR) model, quantitative grading method and analytic hierarchy process (AHP), as well as the combination of the eco-environmental vulnerability index were used to analyze the characteristics of eco-environmental vulnerability of the Pearl River delta at different periods. On this basis, the degree of influence of variable factors on differences in the spatio-temporal distribution of ecological vulnerability was analyzed with the help of factor detection of Geodetector.[Results] ① From 2000 to 2020, the eco-environmental vulnerability index ranged from 1.206 5~4.594 8, indicating slight vulnerability grade. ② In terms of spatial distribution, the vulnerability level was higher in the central part of the Pearl River delta and lower in the eastern and western. In addition, with the increase of elevation, the degree of eco-environment vulnerability tended to decrease on the whole, the proportion of moderate and severe vulnerability decreases. ③ Forest land exhibits potential and slight vulnerability grade, grassland showed moderate vulnerability, cultivated land, water and unused land are mainly located in mild vulnerability areas and construction land showed severe and moderate vulnerability grade. ④ The main factors influencing the spatial variation of eco-environmental vulnerability in the Pearl River delta were population density, NDVI and biological richness index.[Conclusion] Affected by the pressure of population growth, the eco-environmental vulnerability level of the Pearl River delta increased during the study period.

Abstract:[Objective] The spatial database of geological disaster field survey was conducted to analyze the formation mechanism and failure mode of collapse in the area where granite weathered residual soil was developed, to explore the contribution rate of different environmental disaster factors to collapse development, and to evaluate the spatial susceptibility and distribution law of collapse disaster.[Methods] Based on the analysis of the development characteristics of granite weathered residual soil collapse at Baiyun District, Guangzhou City, eight disaster-causing factors closely related to the development of collapse disaster (including elevation, slope, slope direction, topographic relief, distance to stream, rainfall, stratum lithology, and land use) were selected to construct the evaluation index system of collapse disaster susceptibility, and 404 historical collapses in the study area were superimposed. Using the contribution rate model, the collapse disaster sensitivity and spatial distribution characteristics of each index factor were calculated and counted. The modified sample difference of the factor contribution rate of each secondary index was used to determine the factor weight.[Results] ① The contributions of slope, elevation, and topographic relief to collapse susceptibility in the study area were relatively high, while slope direction, stratum lithology and rainfall had low contributions to the assessments of collapse susceptibility. ② The extremely high-prone areas were mainly concentrated in the western foothills, and the collapse susceptibility decreased gradually from the outer edge of the mountain ground line to the center. ③ The collapse rates of the extremely high and high prone areas accounted for more than 85% of the total collapse rate. The model susceptibility evaluation success rate and prediction rate reached 91.3% and 92.6% respectively.[Conclusion] Topography and geomorphic factors of slope had significant impacts on collapse development. The collapse disaster susceptibility evaluation model based on contribution rate could objectively quantify the index factor weight, and the prediction results of the model had high accuracy. The susceptibility zoning conformed to the actual spatial distribution characteristics of collapse development.

Abstract:[Objective] The practical thresholds separating erosive from non-erosive rainfall events were determined to effectively reduce the workload of soil erosion prediction, and to provide references for regional soil erosion prevention.[Methods] Five bare fallow runoff plots packed with typical soils from five water erosion subregions of China were established in the Fangshan District of Beijing City. We used the rainfall erosivity deviation method to derive the two thresholds of rainfall amount (P) and maximum 30-minute rainfall intensity (I₃₀) for each plot based on runoff and soil loss data obtained during 2006-2019.[Results] ① The I₃₀ thresholds were more effective than the P thresholds in identifying erosive rainfall events. ② The erosive rainfall thresholds were highest for the black and cinnamon soil plots, both having P thresholds of 10.0 mm and I₃₀ thresholds of 10.2 mm/h, followed by the loess plot with P and I₃₀ thresholds of 9.5 mm and 8.9 mm/h, respectively. The thresholds were lower for the purple and red soil plots. The corresponding P thresholds were 5.4 and 6.1 mm, respectively, and the I₃₀ thresholds were 3.2 and 5.2 mm/h, respectively. ③ To acquire reliable and stable thresholds, at least 12 years of runoff and soil loss monitoring data were required for each plot.[Conclusion] Erosive rainfall thresholds differed among soils in different regions due to differences in soil properties such as particle size distribution and organic matter content, as well as in local climate factors such as rainfall pattern.

Abstract:[Objective] The coordinated development among the unique ecology, economy, and society of the Loess Plateau was studied to guide the sustainable development of the Loess Plateau.[Methods] The study used data from the typical areas of in Loess Plateau of Changwu County, Suide County, Shenmu City, and Chunhua County from 2001 to 2019 to investigate the ecological, economic, and social development of the area. The coupled coordination degree model and the scissors difference method were used to study the coordinated development trend of the ecology-economy-society system.[Results] The comprehensive evaluation index of the ecosystem for the typical areas of the Loess Plateau fluctuated and increased, the comprehensive evaluation index of the economic system and the social system increased steadily, and the degree of ecological-economic-social coupling and coordination continued to increase. The scissors difference between the ecological and economic systems, and between the ecological and social systems decreased over time, reflecting continuous improvement in the relationships between the ecological, economic, and social systems in the region, and indicating coordinated development. The impact of the economic and social systems on the ecological environment weakened year by year.[Conclusion] Ecological and economic systems, and ecological and social systems of southern border area of the Loess Plateau were in a stage of coordinated development. However, the ecological environment is still an important factor restricting local development. Stabilizing and developing the ecological civilization construction in this region and alleviating the competition between the economy and the ecosystem, and between society and the ecosystem are still important issues that need to be faced for the sustainable development of the Loess Plateau.

Abstract:[Objective] Soil and water conservation and ecological benefits of forest ecosystem in the new urban karst areas of Guanshanhu District, Guiyang City in Central Guizhou Province were studied to scientifically evaluate the achievements of ecological construction, and to provide a scientific reference for the sustainable utilization of resources and the environment, and high-quality development of forests in new urban karst areas.[Methods] The distribution patterns of forest ecosystems at Guanshanhu District at 2000, 2010, and 2020 were extracted by using multi-source remote sensing data. The soil conservation and regulating water amount were calculated by a soil conservation model and the water balance equation. The ecological benefit value was calculated using the market value method and the shadow engineering method.[Results] ① The area of the forest ecosystem at Guanshanhu District increased from 10 892.74 hm² to 15 571.90 hm² during 2000-2010. Forest area decreased with the acceleration of urban expansion, and was 13 937.54 hm² by 2020. Due to the opposing influences of ecological engineering and urban expansion, the forest ecosystem has changed greatly during the past 20 years. ② The value of soil and fertilizer conservation and water regulation in the forest ecosystem generally showed an increasing trend, and the ecological benefits per unit area increased. However, due to the decrease in forest ecosystem area, the ecological benefits of soil and fertilizer conservation and water regulation increased slowly. ③ Soil conservation per unit area followed the order of coniferous forest>mixed coniferous and broad-leaved forest>shrub forest>broad-leaved forest>other forest. The regulated water amount followed the order of coniferous forest>broad-leaved forest>mixed coniferous and broad-leaved forest>shrub forest>other forest. The total value of the ecological benefits of soil fertility and water regulation in coniferous forest was the largest, followed by shrub forest. Shrub forest played a very important role in soil fertility and water regulation.[Conclusion] The forest ecosystem changed greatly at Guanshanhu District, and the area increased significantly from 2000 to 2010, but exhibited a decreasing trend in recent years. However, the per unit area ecological benefits increased continuously, and played an important role in soil and fertilizer conservation and water regulation. Forest ecosystem protection should be given great importance in the development of new urban areas.

Abstract:[Objective] The natural vegetation succession characteristics and influencing factors for a reclamation area in Tianjin City were studied in order to provide a scientific basis for ecological restoration and reconstruction of the reclamation area.[Methods] The plant community types, succession patterns and influencing factors in a reclamation area of Tianjin City were analyzed by field survey and sampling, laboratory measurements and TWINSPAN, detrended correspondence analysis and canonical correspondence analysis, etc.[Results] ① The natural vegetation succession sequence in the reclamation area of Tianjin City followed the order of:Ass. Suaeda salsa →Ass. Phragmites australis+Suaeda salsa →Ass. Aeluropus sinensis→Ass. Phragmites australis→Ass. Tamarix chinensis-Cynanchum chinense. Soil salinity gradually decreased and the number of the plant species gradually increased as succession proceeded. ② Total soil salinity, distance from urban secondary roads, and distance from the 15 m isobath were significantly different in different succession stages, and these were the main factors influencing the primary succession of vegetation in the reclamation area of Tianjin City.[Conclusion] Vegetation succession in the reclamation area of Tianjin City was affected by both natural and human factors. Scientific regulation of environmental factors (e.g. total soil salinity) could provide favorable environmental conditions for vegetation restoration in reclamation areas.

Abstract:[Objective] The the temporal and spatial evolution law of non-point source pollution on cultivated land in the Dongting Lake plain from 2009 to 2019 was studied to define the decoupling relationship between cultivated land non-point source pollution and agricultural production in order to provide a scientific reference for the treatment of non-point source pollution on cultivated land in the Dongting Lake plain.[Methods] The application rates of chemical fertilizers and pesticides in addition to grain yield per unit area were used to describe the status of cultivated land non-point source pollution and agricultural production in the Dongting Lake plain. Spatial analysis and a decoupling model were used to determine the temporal and spatial evolution law and the decoupling relationship between non-point source pollution on cultivated land and agricultural production in the Dongting Lake plain from 2009 to 2019.[Results] ① From 2009 to 2019, the application rates of chemical fertilizers and pesticides in the Dongting Lake plain initially increased and then decreased, and exhibited obvious spatial differences. The productivity of chemical fertilizers and pesticides showed an overall upward trend; ② From 2009 to 2019, grain yield per unit area in the Dongting Lake plain showed an inverted U-shaped trend, with obvious spatial differences; ③ The decoupling relationship between grain yield per unit area and the rates of chemical fertilizer and pesticide applications in the Dongting Lake plain showed obvious stage characteristics:the first stage was a fluctuation period (2009-2013); the second stage was a strong decoupling period (2014-2015); and the third stage was a weak negative decoupling and declining decoupling period (2016-2019); ④ The decoupling relationship between agricultural production and cultivated land non-point source pollution in the Dongting Lake plain gradually showed high convergence and aggregation characteristics on the county-level spatial scale.[Conclusion] Efforts should be taken to further strengthen the prevention and control of the source of non-point source pollution on cultivated land through the use of a variety of measures in order to improve grain yield, and to finally realize the strong decoupling between cultivated land non-point source pollution and agricultural production.

Abstract:[Objective] The differences of agricultural water use efficiency and its influencing factors between the Yellow River basin and the Yangtze River Economic Belt were studied in order to provide a scientific basis and reference for decision-making to effectively improve agricultural water use efficiency and sustainable agricultural development in the two regions.[Methods] Based on data from 19 provinces and cities in the Yellow River basin and the Yangtze River Economic Belt from 2009 to 2019, differences in agricultural water use efficiency and its influencing factors were analyzed by use of the super-efficiency SBM model, the Malmquist index, kernel density estimation, standard deviation ellipse, Tobit regression and other methods.[Results] ① Agricultural water use efficiency increased over time. The annual efficiency value for the Yellow River basin fluctuated greatly and internal differences were obvious. The efficiency center oscillated at the border between Shanxi Province and Shaanxi Province. However, the annual efficiency value for the Yangtze River Economic Belt fluctuated slowly, and its efficiency center moved to the southwest over time, and the annual average efficiency value was slightly higher than the efficiency value observed for the Yellow River basin. ② Technological progress was the main reason for the change in agricultural water use efficiency. The technological progress index for the Yellow River basin was slightly higher than the index of the Yangtze River Economic Belt from 2009 to 2019. ③ There was a great difference in the factors influencing the increase in agricultural water use efficiency over time between the two regions, and the reasons for the difference are closely related to the natural geographical environment and economic development.[Conclusion] Agricultural water use efficiency in the Yellow River basin and the Yangtze River Economic belt is generally good, but there are great regional differences. Therefore, targeted measures should be taken according to local conditions, and the efficiency of agricultural water use in the two regions should be promoted and continuously optimized from the perspectives of scientific and technological input, government guidance, and farmers' participation so as to produce sustainable development of river basin agriculture.

Abstract:[Objective] The trend and driving factors of desertification change in the Aksu region from 2009 to 2019 were studied in order to provide a scientific basis for ecological restoration in the region and for formulating desertification control policies according to local conditions.[Methods] A desertification evaluation index system was constructed based on the Sixth National Rules for Monitoring Desertification. The trend in desertification change in the Aksu region from 2009 to 2019 was evaluated with ArcGIS and IDRISI software, and the driving factors of desertification were analyzed and the predictions were made.[Results] ① The desertification area in the Aksu region decreased over time from 2009 to 2019, and desertification declined. Desertification in the Aksu region showed strong spatial heterogeneity, and the area of extremely severe desertification was located in the southern part of the study area bordering the Taklamakan Desert. The extremely severe desertification area accounted for the largest proportion of the desertification area. ② The results of the single driver analysis of desertification in the Aksu region from 2009 to 2019 showed that land use type was the most important factor influencing desertification in the Aksu region, and the interaction of multiple drivers had stronger explanatory power on desertification evolution than any single factor. The mode and intensity of action showed enhancement and non-linear enhancement, respectively. ③ The prediction results from the CA-Markov model showed that if the driving factors did not change, the degree of desertification in the Aksu region would continue to reverse during 2019-2024, and the overall change for the area would be from extremely severe desertification to severe desertification. The desertification area would expand in some regions.[Conclusion] The desertification area in the study area decreased during the study period, and the desertification degree declined. The main factor affecting desertification was land use type. Desertification control as well as ecological restoration projects should be carried out to reasonably and effectively control and prevent desertification by focusing on combinations of the desertification driving factors.

Abstract:[Objective] The regional ecological environmental effects caused by land use changes in Nanchang City by determining the quantitative relationships between regional land and resource development and ecological environments were analyzed in order to providing support for regional ecological environmental protection, ecological civilization construction, and green development.[Methods] The temporal and spatial change trajectory of land use changes was calculated by using a land use transfer matrix and a nuclear density analysis model. The impact of land use changes on the ecosystem was deduced by an eco-environmental quality index and the ecological contribution rate.[Results] ① From 2000 to 2020, the land use change in Nanchang City was mainly from grassland and cultivated land to construction land, from forest land and water area to cultivated land, and from cultivated land to water area; ② From 2000 to 2020, the spatial agglomeration evolution of land use change in Nanchang City was mainly concentrated in the northwest, and the conversion of cultivated land to water area was the main reason for the improvement of the ecological environment in the study area. The conversion of water area to cultivated land, and cultivated land to construction land were the main reasons for the degradation of the regional ecological environment.[Conclusion] The eco-environmental quality index of Nanchang City in 2000, 2010 and 2020 was 0.354, 0.351, and 0.352. This index was relatively stable, but the eco-environmental quality index in the region showed a downward trend. It will be necessary to strictly control the boundary of urban development and to implement an ecological red-line protection policy in the future.

Abstract:[Objective] The characteristics of a typical Tamarix hohenackeri shrub resource island in Nuomuhong area of Qaidan Basin under the action of prevailing winds were studied in order to deeply understand the ecological significance of tamarisk shrubs in similar habitats, and to provide a reference for saline-alkali land improvement and ecological protection of desert-oases.[Methods] Measurements of soil organic carbon (SOC), soil moisture content (SMC), soil pH value, and EC values in different soil layers to a depth of 110 cm at positions under the canopy, at the edge of the canopy, and in open areas were made by systematically sampling the soil surrounding typical tamarisk shrubs in the desert-oasis transition zone in the Nuomuhong area of the Qaidam Basin.[Results] ① The litter and underground biomass around the shrub and under the canopy were significantly greater than at the edge of the canopy in the open space. SOC under the canopy was significantly greater than at the canopy edge, exhibiting the characteristics of a resource island; ② SMC under the canopy in the leeward direction and SOC of the leeward canopy edge and open space were significantly greater than in other directions, and the soil pH values of the 0-5 cm soil layer at the canopy edge were lower; ③ The aboveground biomass and litter at the edge of the canopy were significantly greater in the leeward direction than in other directions, which in turn reduced water evaporation and increased SOC.[Conclusion] The soil around the shrub not only exhibited the characteristics of a resource island under the canopy, but also resulted in SMC, SOC contents, and lower soil pH value that were more suitable for plant growth in the leeward direction, and therefore could be called a resource island in the wind shadow area.

Abstract:[Objective] The correlation between land use changes and ecosystem service values were assessed to provide references for formulating appropriate land intervention policies.[Methods] The five-period land use data of the Irtysh River basin and the CLUE-S model were used to quantify the temporal and spatial variation of ecosystem service value profit and loss under land use change.[Results] ① The conversion of grassland and forest land to other land continued from 2000 to 2018 in the Irtysh River basin, and the cultivated land area increased significantly. By 2030, the proportion of arable land in this basin would increase by 4.92% (from 1 502.48 km² to 4 070 km²), while the forest land area decreased rapidly by 7.18% (from 7 547.26 km² to 5 424.36 km²). ② The value of ecosystem services in the Irtysh River basin increased from 51.816 billion yuan in 2000 to 183.244 billion yuan in 2018. By 2030, the value of ecosystem services would be in a fluctuating downward trend (177.786 billion yuan in 2030). ③ Forest land and grassland were converted to cultivated land, and the resulting loss in ecosystem service value in the Irtysh River basin was expected to reach 10.880 billion yuan, followed by grassland conversion loss (3.439 billion yuan) > forest land conversion loss (2.849 billion yuan) > water area conversion loss (1.831 billion yuan). ④ The spatial distribution of ecosystem service value gains and losses in the Irtysh River basin showed a pattern of "high in the north and low in the south", and the value gains and losses showed positive spatial autocorrelation, both globally and locally.[Conclusion] Human factors led to the occupation of a large amount of ecological land, a decline of ecosystem service value, and significant spatial heterogeneity of profit and loss. It is necessary to undertake further effective ecological protection and compensation policies to promote the livelihood transformation of farmers and herdsmen, and to reduce their dependence on the natural environment.

Abstract:[Objective] The vegetation change and important climate factors influencing fractional vegetation coverage (FVC) in Sichuan Province were analyzed in order to provide theoretical support for the sustainable development of natural resources in this area.[Methods] Based on the MODIS-NDVI dataset for Sichuan Province from 2000 to 2020, FVC for the study area from 2000 to 2020 was statistically analyzed, and its spatiotemporal variation characteristics and relationships with climate factors were analyzed.[Results] ① The FVC of Sichuan Province tended to be stable, and the average FVC value was about 0.50. ② FVC exhibited obvious spatial heterogeneity. FVC in the east was higher than in the west, and presented an increasing spatial distribution pattern from northwest to southeast. ③ The areas with high FVC in Sichuan Province accounted for about 70% of the total area, and the overall vegetation status was good. There were signs of slow growth in FVC over time. ④ FVC changes in the study area were positively and negatively correlated with air temperature and precipitation, and the area proportions were close to each other. ⑤ The driving forces of FVC change in Sichuan Province were mainly non-climate factors, and the area driven by climate factors accounted for 21.17% of the total area.[Conclusion] Sichuan Province has complex topography. The good climatic conditions, vigorous vegetation growth, and stable FVC experienced over a period of many years has maintained the ecological environment of the middle and upper reaches of the Yangtze River. In the future, Planners and officials should give more attention to the impacts of human activities FVC, and actively build an ecological barrier in the middle and upper reaches of the Yangtze River.

Abstract:[目的] 研究人类活动对近年来鄱阳湖流域陆地植被覆盖变化的作用机制，为推动该流域乃至长江流域生态系统健康发展提供理论依据。[方法] 基于鄱阳湖流域最新MODIS增强型植被指数(EVI)数据产品，并结合气象数据以及土地利用和人口数据，采用趋势分析、残差分析、相关分析等方法，分析研究区2000—2020年流域陆地植被覆盖变化特征，深入探讨了人类活动作用的影响机制。[结果] 近20 a来鄱阳湖流域地表植被状况明显改善，植被EVI呈显著上升趋势(p<0.05)；流域人类活动整体上对植被EVI的增加起着重要的促进作用。在城镇化新扩张区域表现出明显的抑制作用；在流域尺度上，人类活动对EVI增长的贡献率达到32.48%，不同子流域间人类活动的平均贡献率为30%～43%。鄱阳湖流域植被EVI及其残差趋势在人口密度增加0～100人/km²和400～500人/km²时，分别出现了一个峰值。这一结果主要得益于近年来江西省社会经济快速发展和生态文明建设理念的驱动，广大乡村地区人口密度的小幅增加(0～100人/km²)比单纯的人口流失区更能有效改善地表植被状况。与此同时，城市区域人口密度增加幅度在一定区间时(400～500人/km²)也能促进地表植被状况的改善。[结论] 人类活动是地表植被覆盖变化的重要促进因素，高质量发展中的“绿色”“协调”理念对生态环境的改善至关重要。

Abstract:[Objective] The temporal and spatial variation characteristics and their the influencing factors of cultivated land conversion in Yan'an City from 2000 to 2020 were analyzed in order to provide a theoretical basis for policy-making regarding cultivated land protection and prevention of farmland conversion.[Methods] Land-use and land-cover change data for 2000, 2005, 2010, and 2020 were analyzed to reveal the degree and causes of non-agriculturalization in the Loess Plateau. The research was carried out by using the methods of kernel density estimation and geodetector.[Results] ① From 2000 to 2020, the non-agricultural area of cultivated land in Yan'an City changed following a pattern of increase-decrease-increase. The total non-agricultural area was 7 865.28 hectares, and the non-agricultural conversion rate of cultivated land was 8.45%. ② From 2000 to 2020, cultivated land conversion in Yan'an City was mainly located along the river valleys of the Luohe River and the Yanhe River. The non-agricultural conversion of cultivated land was concentrated in the central and southern regions, with a maximum kernel density of 155.03 located near Yan'an New City, Baota District. The sub-concentration areas of non-agricultural cultivated land were Huangling County and Luochuan County, with maximum kernel densities of 75.95 and 51.77, respectively. ③ The phenomenon of non-agriculturalization of cultivated land in Yan'an City mainly occurred in areas with low slope, medium altitude, and low topographic index. ④ The most important factors affecting the conversion of cultivated land in Yan'an City were urban population, registered population, and gross domestic product, with explanation rates of 68.65%, 68.45%, and 66.54%, respectively.[Conclusion] The phenomenon of cultivated land conversion in Yan'an City from 2000 to 2020 was significant. The temporal changes were volatile, and the spatial heterogeneity was strong due to the comprehensive effects of nature, population, and social economy.

Abstract:[Objective] The temporal and spatial evolution characteristics of ecological sensitivity in a typical coal mine resource city (Liupanshui City in Guizhou Province) in a karst region from 2000 to 2020 were analyzed in order to provide a basis for the ecological protection of coal mine resource cities in karst regions.[Methods] We chose a remote sensing ecological index, a water loss and soil erosion sensitivity index, a rocky desertification sensitivity index, a landscape development intensity index, and an index of carbon emissions to build an integrated ecological sensitivity index, and analyzed the ecological sensitivity of Liupanshui City with the aid of spatial autocorrelation analysis.[Results] ① From 2000 to 2020, the extremely sensitive, highly sensitive, mildly sensitive, and moderately sensitive areas in Liupanshui City showed a trend of fluctuation and decline, while the insensitive areas continued to rise. The ecological environment of Liupanshui City improved significantly over time. ② From 2000 to 2020, the spatial evolution trend of extremely sensitive and highly sensitive areas in Liupanshui City was scattered over the entire city, shifted to the southeast, and spread to the northwest, and the area continued to shrink. Except for the slight spread in the south of Zhongshan District, other areas showed a continuous or fluctuating shrinking trend, and the environment tended to improve. ③ From 2000 to 2020, the Global Moran's I values for Liupanshui City were 0.525, 0.570 and 0.476, respectively, indicating that the ecological sensitivity of Liupanshui City had a positive spatial correlation, and the correlation gradually weakened with time. The LISA diagram showed that the high and low aggregation areas decreased, and the degree of ecological sensitivity aggregation decreased.[Conclusion] The ecological sensitivity of Liupanshui City is mainly mild, mainly distributed in the northwest region with better ecological conditions. The proportion of extremely sensitive areas was small, concentrated in the southeast where the natural conditions are more fragile. With the passage of time, afforestation and other engineering measures in Liupanshui City have alleviated the environmental deterioration caused by excessive human intervention to a certain extent, reducing the area of extremely sensitive and highly sensitive areas in the region and significantly improving the ecological environment.

Abstract:[Objective] Land use change and habitat quality in Nanyue key ecological function area of Hu'nan Province were studied to reveal the relationship between forest land reduction and habitat quality caused by human activities, in order to promote the coordinated development of ecological protection and economic construction in this area.[Methods] The land use transfer matrix was obtained based on the land use change data of 2009, 2012, 2015,2018 and 2021, and the spatial-temporal distribution characteristics of land use structure and habitat quality in Nanyue key ecological function area were analyzed and predicted by InVEST model and CA-Markov model. Bivariate spatial autocorrelation was used to explore the correlation between forest land and habitat quality.[Results] ① From 2009 to 2021, forestland and cultivated land in the study area were mainly transferred to construction land. The area of construction land increased by 15.87%, among them, 45.37% and 36.25% were transferred from forestland and cultivated land respectively. ② From 2009 to 2021, the spatial distribution of habitat quality in this region was higher in the west and lower in the southeast. ③ The positive correlation between the spatial distribution of forest land and habitat quality in the study area gradually increased, and the high aggregation of forest land and excellent habitat quality was the main type. ④ The construction land in Nanyue District will increase by 4.36% in 2025 and reach 1 563.53 hm² in 2030. The quality of habitat will slowly decline in the future.[Conclusion] The change of habitat quality is closely related to the decrease of forestland and expansion of construction land caused by human disturbance. Therefore, resource and environment control should be strengthened in Nanyue key ecological function zones.

Abstract:[Objective] The spatial and temporal evolution of productional-living-ecological functions was studied in order to provide a scientific basis for the construction of new regional land space patterns, implement and supervise territorial spatial planning, and ensure regional food security.[Methods] Functional integration, geographic grid sampling, and spatial coordination degree model methods were comprehensively applied to analyze land use remote sensing data from 1990, 2005, and 2020 in the Huanghuaihai Plain of He'nan Province with regard to the state and coordination characteristics of productional-living-ecological functions in the study area.[Results] From 1990 to 2020, the production and living function indexes increased by 1.30% and 20.83%, respectively, and were characterized as being low in the east and high in the central and east parts of the study area. Over the same time period, the ecological function index decreased by 2.52%. The production service functions were mainly in a relatively balanced state. The shrinking areas were mostly located in the southwest, and the expanding areas were concentrated in the west and the east. The variation of the living function was small, and the spatial distribution was scattered. The spatial variation of the ecological function was strong, with the shrinking area concentrated in the southwest. The expanding area comprised a circular distribution along the northwest, west, and south. The coordination degree of regional land function gradually deteriorated, and the area of middle-high and high-coordination areas were small. The area of low-coordination areas expanded rapidly, and became the most important type of regional land spatial function coordination. The area proportion of middle-low and middle-coordination areas continually decreased.[Conclusion] According to the functional service characteristics of the territorial space in the study area, the development and utilization of the territorial space should be reasonably coordinated and deployed, so as to promote the coordinated development of production, living and ecological functions of territorial space.

Abstract:[Objective] The spatial and temporal changes in the intensive use of arable land in Inner Mongolia Autonomous Region were studied in order to improve the intensive and sustainable use of arable land resources.[Methods] Principal component analysis was used to comprehensively evaluate the level of intensive use of arable land for the entire Inner Mongolia region and its 12 leagues, and to reveal its spatial and temporal variation characteristics and driving factors.[Results] ① The analysis conducted at the whole region level showed that the overall arable land intensification level increased during 1985-2018, with the arable land intensification level increasing from 63.30 to 88.12, an increase of 39.21%. The overall arable land intensification utilization showed a wave-like growth pattern. ② The spatial-level analysis showed that the level of intensive utilization of arable land in each league or city of Inner Mongolia could be divided into five levels by the natural division method, among which Bayannaoer and Hulun Buir League were classified as highly intensive (level Ⅰ); Xilingol League, Hing'an League, Alxa League, and Ordos City were relatively high intensive (level Ⅱ); Hohhot City was generally intensive (level Ⅲ); Chifeng and Tongliao City were relatively extensive (level Ⅳ). Wulanchabu City, Baotou City, and Wuhan City were extensive (level Ⅴ). ③ The analysis of drivers showed that GDP per capita, posable income per farmer, financial expenditures on agriculture, and the amount of investment in fixed assets in primary industries had significant positive driving effects on the intensive use of arable land in Inner Mongolia, while the gross value of primary industries, urbanization rate, and the area of water and soil management had significant negative driving effects on the intensive use of arable land in Inner Mongolia.[Conclusion] In the future, transfer of arable land should be regulated, the control of arable land use should be strengthened, the relationship between production and ecology should be coordinated, and the intensive use of arable land should be further improved.

Abstract:[Objective] The developing history of soil erosion research in China was reviewed, the major research achievements were summarized, and the current problems and key research fields in the future were analyzed to provide a reference for China's soil and water conservation, regional ecological construction, and high-quality green development.[Methods] Based on years of work experiences from field investigations and academic research on soil erosion, long-term consideration has been given to major issues related to soil erosion in China through numerous academic discussions and communications with leading experts.[Results] A series of major research achievements have been obtained in the field of soil erosion in China during the last one hundred years, but there have also some drawbacks and problems. In the future, soil erosion research in China should focus on several key fields, such as the improvement, promotion, and accuracy evaluation of soil erosion prediction models; calculation methods and model construction for slope runoff; evaluation of the representativeness and validity of results from simulated rainfall and flume scouring experiments; and so on. More attention should be given to the mechanisms of soil erosion processes, model applications, technical methods, response evaluations, bottleneck problems, and other issues.[Conclusion] Researches over the past century has shown that soil erosion research should be conducted based on national conditions. Symbolic achievements could only be achieved by determining and adjusting research directions according to the characteristics of soil erosion, the research status, and the changes in social demands in China. Meanwhile, in the new era when the country is vigorously promoting the construction of ecological civilization, soil erosion research must be refreshed with new ideas and emphases. Moreover, soil and water conservation practices should also be integrated with rural revitalization and ecological construction by giving priority to soil erosion prevention and reducing disturbance to soil. Besides, we should change the previously used model of instituting laws and regulations after soil destruction and water loss occurred.