Abstract:[Objective] The impacts of the gully reclamation project in Northern Shaanxi Province on the distribution of cropland and vegetation restoration were studied in order to provide scientific reference for the direction and optimization of cultivated land remediation in similar area.[Methods] Taking the Yan'an Gutun watershed of Yan'an City as a case study, based on ArcGIS and ENVI, visual interpretation and kernel density estimation was used, and NDVI were calculated.[Results] ① After the gully reclamation project, the cropland was more concentrated in valleys, the fragmentation of cropland was decreased, and the quality of cropland was improved. ② The proportion of low-slope cropland was increased. The structure of cropland had been optimized, but the high-slope cropland still occupied a certain amount and needed to be further optimized. ③ Based on the analysis of kernel density, the area of the middle and low density zone with high cropland quality increased, and the area of the middle and high density zone with low cropland quality decreased. The proportion of high-quality cropland increased. ④ Overall, NDVI in the Gutun watershed showed the law of "low at the foot of the hill while high on the hill". The vegetation situation in the watershed was improved after the gully reclamation project. ⑤ The vegetation in the area of returning farmland to forests and the slope control section had been improved well.[Conclusion] To a certain extent, the gully reclamation project has improved the quality of cultivated land and vegetation situation, but there are still some problems such as soil erosion, salinization and slope instability, etc. Gully reclamation project should be based on the construction of ecological civilization, weigh the advantages and disadvantages of various aspects and serve the high-quality development of the Loess Plateau.

Abstract:[Objective] We aim to investigate the effects of gravel content on soil erosion and water hydrodynamic characteristics of steep slope project.[Methods] The relationship between soil erosion change rate and soil erosion rate and hydrodynamic parameters was studied by means of indoor simulated rainfall experiment and artificial soil preparation, at 50° engineering slope with 5 kinds of gravel content(3%, 15%, 35%, 55%, 75%) under 3 rainfall intensity(40, 60, 80 mm/h).[Results] ① With 40, 60, 80 mm/h rain intensity, the slope runoff rate of each gravel content was decreased by 10.1%~55.9%, 13.9%~41.9%, 19.6%~47.7% compared with that of soil slope. Runoff shear force, runoff power and unit energy of runoff section showed a linear, exponential and power function relationship with gravel content, respectively. ② The erosion rate of slope decreased with the increase of gravel content, and the amount of erosion rate and the change process of different experimental rain intensity showed obvious difference. When the rain intensity was 40 mm/h, the overall sediment yield of the slope was low, and the rainfall duration showed a slow increase trend. When the rain intensity was 60 mm/h, the erosion rate increased rapidly under different gravel content, and then fluctuated. When the rain intensity was 80 mm/h, the gravel content was 3%, the growth rate of slope decreased rapidly after rapid growth. And when the gravel content was greater than 15%, the slope erosion rate began to decline slowly after reaching the peak value. ③ The soil erosion rate showed a significantly linear function, logarithmic function and power function relation with runoff rate, runoff shear force, runoff power and the unit energy of the water section of the project slope.[Conclusion] The soil gravel of engineering slope has anti-erosion effect, and with the increase of gravel content, the soil erosion amount and the hydrodynamic parameters of slope are reduced significantly.

Abstract:[Objective] The effects of conservation tillage on crop yield and soil erosion in sloping land of yellow soil were analyzed in order to provide scientific basis for soil and water loss control an agricultural sustainable development in Guizhou Province.[Methods] In the typical slopping land of yellow soil in southwest China, nitrogen and phosphorus loss, surface runoff and soil nutrient content were investigated under different tillage systems from 2017 to 2018. Six monitoring plots were set up, including no fertilization + downslope conventional tillage(TR₁), conventional fertilization + downslope conventional tillage(TR₂), optimized fertilization+downslope conventional tillage(TR₃), optimized fertilization +cross ridge tillage(TR₄), optimized fertilization +cross ridge tillage + straw mulching(TR₅), optimized fertilization + cross ridge tillage + straw mulching + contour hedgerow(TR₆).[Results] ① Compared with TR₃, the runoff of TR₄, TR₅, TR₆ were reduced by 59.72%, 74.13% and 89.18% respectively, and the total loss of nitrogen and phosphorus showed a same varying trend. ② TR₅ and TR₆ had the greatest impact on total nutrient content, of which total nitrogen was 20.00% and 23.67% higher than TR₄, 23.53% and 27.31% higher than TR₃, respectively. ③ Maize yield stability(SI) and sustainability(SYI) were the best with TR₄, TR₅ and TR₆ treatments while maintaining a high yield. ④ The yield of maize and rape was significantly and positively correlated with total nitrogen, total phosphorus, available phosphorus and organic matter(p<0.01), and positively correlated with available nitrogen(p<0.05), while negatively correlated with nitrogen loss, phosphorus loss and runoff(p<0.01).[Conclusion] Conservation tillage in sloping land could effectively reduce surface runoff, the loss of nitrogen and phosphorus, maintain the soil nutrient fertility and promote high yield of crops, and achieve a stable and sustainable production, and the effect of comprehensive conservation tillage measure is greater than that of single conservation tillage measure.

Abstract:[Objective] The effects of oil pollution on soil water holding capacity and water supply intensity were studied in order to provide a theoretical basis for the study of organic pollutants migration and transformation in soil.[Methods] The main soil type (loessial soil) in the oil-producing area of northern Shaanxi was used as the test material, and five different levels of polluted soil (0, 0.5%, 1%, 2%, and 4%) were obtained by artificial simulation. The soil water retention curve obtained for each treated sample was analyzed using the van Genuchten model, to investigate the difference of soil water-holding capacity, water availability and specific water capacity among different treatments.[Results] The water-holding capacity of soil was significantly reduced by oil pollution, and the greater the pollution concentration was, the lower the water-holding capacity was. Oil pollution had a significant influence on the soil water characteristic curve in the low suction section of pF1.5 and the high suction section above pF3.5, and its influence on soil structure was more significant. The high concentration of oil pollution caused the decrease of soil water availability, exacerbated soil desiccation, which was not conducive to the coordination of the contradiction between the arid climate and the water demand of plants. With the increase of oil pollution concentration, the soil specific water capacity also showed a significant decreasing trend, and the suction range corresponding to soil available water was narrowed.[Conclusion] Oil pollution has significantly reduced the soil water-holding capacity and water supply intensity, exacerbated soil drought and brought serious harm to plant production and ecological environment.

Abstract:[Objective] The influence of topography on the diversity and distribution pattern of plant species in karst areas was studied, in order to provide scientific basis for ecological protection and maintenance in this region.[Methods] Variance analysis was used to study the species diversity of trees, shrubs and herbs under different topographic in Shibing karst area of Guizhou Province, and canonical correspondence analysis(CCA) was used to study the effects of topographic factors on their distribution patterns.[Results] The evenness of trees at the top of mountain was significantly lower than other slopes, while the dominance was significantly higher than other slopes. The diversity of shrubs at the top of mountain was significantly higher than that at the downhill and valley. The richness at the top of mountain was significantly higher than that at the middle slope, downhill slope and valley, and the uphill was significantly higher than that of the downhill and valley. The dominance of valley was significantly higher than that of the top of mountain. The diversity of herbs was significantly lower at the top of mountain than that at the middle slope, downhill and valley. The richness was significantly lower at the ridge and the top of mountain than that at the middle slope, downhill and valley. The dominance was opposite to the diversity. The richness of herbs in semi-shady slope was significantly higher than that in semi-sunny slope. The influence of slope on the richness and diversity of trees was consistent, the flat slope was significantly higher than those on the gentle slope and slope, and steep slope was significantly higher than those on slope. The evenness of slope was significantly lower than those on flat slope and steep slope, while the dominance was opposite to the evenness. The CCA results showed that, elevation and slope had significant influence on the distribution pattern of the three types of growing plants while slope direction had no significant influence. Slope position had significant influence only on the distribution pattern of tree species.[Conclusion] The diversity and distribution pattern of plant species in karst areas are influenced by many factors, elevation and slope are the main influential factors, and slope position and slope direction are the secondary influential factors.

Abstract:[Objective] The effects of temperature and material ratio on urban landscaping waste and chicken manure water bath aerobic composting were studied in order to provide technical guidance and theoretical basis for large-scale aerobic composting.[Methods] A water bath temperature-controlled aerobic composting device was constructed with water bath incubator, air pump, gas rotameter, thermometer, fermentation bottle and a gas bottle. Water bath composting with different ratios of urban gardening waste to chicken manure of 2:3, 2:1, 3:1, and 5:1 (named A, B, C, and D, respectively) was set.[Results] The optimal temperature range of microbial metabolic activity was 50~55℃. The degradation of organic matter by microbes was significantly inhibited at temperature ≥ 55℃. All four treatments experienced the heating phase, high temperature phase, cooling and medium temperature phases. The nitrogen loss rate in treatments A-D was 47.11%±0.55%, 63.82%±1.05%, and 53.43%±0.71%, and 36.38%±0.83%, respectively. Obviously, the highest nitrogen retention was achieved in treatment D. The seed germination rate and germination index were also evaluated. The germination rate of composting products in treatments A-D was 96.7%±2.11%, 96.7%±2.25%, 84.4%±1.98% and 96.7%±2.06%, respectively, and all of which reached the criteria of maturity (≥ 80%).[Conclusion] The optimum temperature of urban landscaping waste and aerobic compost with chicken manure water bath was 50~55℃, and the nitrogen retention was the highest in group D. The compost products of the four groups all reached the evaluation standard of maturity.

Abstract:[Objective] The species composition and soil characteristics of Nitraria tangutorum community in the artificial water transfer area of Qingtu Lake was studied, in order to reveal the health status of shrub ecosystem in the study area, and to provide scientific basis for scientific protection of shrub sand pile, ecological restoration and desertification control in the study area.[Methods] Based on field vegetation survey, the physical and chemical properties of soil at different distance from water surface were studied.[Results] ① There were 18 species of plants belonged to 6 families and 17 genera in the investigated community, including 8 species of annual herbs, 6 species of perennial herbs and 4 species of shrub plants. The community structure was simple. ② The soil moisture content in 0-60 cm soil layer at different distances from the water surface showed a gradual increase trend with the increase of soil depth. As the distances were increased from the edge of the water surface, the soil moisture content of Nitraria tangutorum sand pile decreased gradually and became stable after 200 m. The mechanical composition of soil was mainly fine sand and coarse sand, and clay particle content iwas relatively low. From the water surface 0-100 m, the content of coarse sand was decreased in the 0-40 cm soil layer and the clay power particle content was great. ③ The artificial water transfer area of Qingtu Lake belonged to the area of fluvial sand, which was seriously deficient in the soil nutrients. The contents of all nutrients were low and uneven, and the soil was in a status of alkalinity. The accumulation of soil organic carbon, total nitrogen and rapidly available potassium was obvious. Within the same distance from the water surface, the content of total phosphorus, total potassium, alkali-hydrolyzed nitrogen and available phosphorus showed no siginificant difference(p>0.05), and the change was not obvious with the increase of soil depth. ④There was a positive correlation between organic carbon content and soil total nitrogen, total phosphorus, available potassium and electrical conductivity(p<0.05), and there was a significant positive correlation between electrical conductivity and total nitrogen, total phosphorus and available potassium(p<0.01), while there was no significant correlation between soil available nutrient content and the total content of corresponding elements(p>0.05).[Conclusion] The vegetation community structure with different distance from water surface is simple, and many species belong to single genus and single family. Water surface formation area affects the soil water content of Nitraria tangutorum sand pile, and enhances the settlement of fine sand particles in the area near water surface. Soil nutrient content is generally low and uneven, and the phenomenon of "surface accumulation" is obvious.

Abstract:[Objective] The effects of plastic film mulching and hole sowing rate on soil water and soil salt distribution of spring wheat under hole sowing were studied in Hetao Plain, in order to provide scientific guidance for reducing soil salinization, improving soil water use efficiency, realizing precision sowing and promoting plastic film spring wheat production.[Methods] Spring wheat in open field with different hole sowing rate (8, 10, 12, 14 and 16 seeds, respectively) was taken as control, to monitor the effect of spring wheat with film mulching on soil moisture, soil salt distribution and the yields of wheat.[Results] The soil moisture in both film mulched fields and open fields decreased with the increase of hole sowing rate, and the difference of soil moisture among different hole sowing rate from sowing to filling period increased with the growth of spring wheat. Under the same how sowing rate, the soil moisture in film mulched fields were higher than those in open fields before the booting period, while it was lower after flowering period. Soil water consumption of spring wheat with film mulching were slightly higher than those in open fields in the whole growing season. The soil salt in both open fields and film mulched fields decreased with the increase of hole sowing rate, however, there was no significant difference among different hole sowing rates. Soil salt in 0-30 cm soil layer in film mulched fields was significantly lower than those in open fields, but the soil salt below 30 cm soil layer was basically the same as those in open fields under the same hole sowing rate. The soil water use efficiency in both open fields and film mulched fields increased with the increase of hole sowing rate. The yields, water use efficiency and water output rate of spring wheat with film mulching were higher while the thousand grain weight and economic coefficient were lower than those in the open fields under the same hole sowing rate. The yield and water output rate in open fields were the highest with a hole sowing rate by 14 seeds, while the yield in film mulched fields was the highest with a hole sowing rate by 12 seeds, and the water output rate was the highest with a hole sowing rate by 10 seeds.[Conclusion] Film mulching can reduce soil salt in 0-30 cm soil layer and improve soil water use efficiency. The suitable hole sowing rate of spring wheat with film mulching should be 70% to 84% of the local conventional open field strip sowing rate, i. e. 10 to 12 seeds per hole sowing in salinized soil in Hetao Plain.

Abstract:[Objective] The effects of litter cover on soil evaporation in the Rhododendron delavayi forest in Baili azalea scenic area were studied, in order to provide a scientific basis for the function of water conservation under the forest.[Methods] According to the theory of soil evaporation, a self-made micro evaporation and infiltration device was used to conduct the simulation experiment. The existing status of litter under the Baili rhododendron forest was taken as a reference, to study the effect of litter with different mass and different proportion on the inhibition of soil evaporation.[Results] The evaporation of soil water decreased with the increase of litter mass at different decomposition degrees and with the same litter coverage ratio. The evaporation of soil moisture decreased with the decrease of soil moisture contents. When the moisture contents decreased by 0.5%, the evaporation of soil moisture with litter cover of 60 g, 30 g and 15 g decreased by 0.11 g, 0.49 g and 1.23 g, respectively. When the cover quality of litter was the same, the inhibition of litter with different decomposition degrees on soil water evaporation was different, which showed as follows:undecomposed > semi-decomposed > decomposed.[Conclusion] The more litter cover, the greater the inhibition of soil evaporation; the lower the decomposition degree of litter, the better the inhibition of soil evaporation.

Abstract:[Objective] The evolution process of soil quality in apple orchard was investigated, in order to provide the basis for the management and development of apple orchard, the sustainable development of apple industry and the poverty alleviation in desertified area of Ningxia Hui Autonomous Region.[Methods] We selected apple plantations of 2 years, 5 years, 10 years and 25 years as the study sites, and the adjacent waste land as the control (CK), to investigate the changes of soil physical and chemical properties and their correlations. Soil comprehensive quality index was analyzed, in order to assess the soil quality.[Results] ① With the increase of plantation age, soil moisture content, electrical conductivity, total nitrogen, organic carbon, available potassium, available phosphorus and hydrolytic nitrogen all increased, while soil C:N and soil temperature all declined. Soil clay and silt, soil pH value and soil selenium content increased in initial stage and then declined, while soil bulk density decreased firstly and then increased subsequently, and the maximum value(peak or trough value) appeared at 10 years. There was no significant difference between soil porosity in different cultivation age of apple plantations. ② Soil coarse sand and soil clay and silt were negatively(p<0.01) correlated with soil temperature and soil C:N ratio, and there was a positive(p<0.01) correlation between soil moisture content, total nitrogen and organic carbon. In contrast, there was a positive(p<0.01) correlation between soil coarse sand and soil available potassium and hydrolytic nitrogen. Soil moisture content was negatively(p<0.01) correlated with soil temperature and soil C:N, and there was a positive correlation between soil total nitrogen, organic carbon, available potassium and hydrolytic nitrogen. Soil bulk density was a negatively(p<0.05) correlated with soil clay and silt, soil moisture content, total nitrogen and organic carbon. There was a positive correlation between soil nutrients, whereas there was no correlation(p>0.05) between soil porosity, soil selenium and other indicators. ③ According to the soil physical, chemical and nutritional indexes, the soil quality comprehensive index was ranked as:25 years > 10 years > 5 years > 0 > 2 years > CK.[Conclusion] The physical and chemical properties of soil can be improved by planting apple economic forests in Ningxia desertified regions for 5 years, and soil quality and soil selenium can be improved significantly in 10 years. With the increase of planting years, soil quality can be improved continuously in Ningxia windy desert area.

Abstract:[Objective] The characteristics and spatial variation of soil erosion in karst plateau mountainous areas were investigated, in order to provide scientific basis for the prevention and control of soil erosion in accordance with the environment of karst mountainous areas.[Methods] Libo County of Guizhou Province, a key ecological function area in typical karst mountainous area, was taken as the research area. The spatial distribution of topographic relief and soil erosion sensitivity and their relationship were analysed by ggeospatial analysis method, to determine the best analysis unit for extracting topographic fluctuation degree, and the evaluation method of soil erosion sensitivity.[Results] Based on DEM data with 10 m spatial resolution, the optimal grid size for extracting topographic relief was 54×54, and relief degree of land surface(RDLS) was between 0.32 and 2.12. The sensitivity of soil erosion in Libo County was mainly slight erosion, which accounted for 88.40% of the total area of the county. In addition, the sensitive area of soil erosion was mainly concentrated in the RDLS range of 0.7~1.7. The RDLS ranged from 1 to 1.5 was the most sensitive response to soil erosion, and thus the dominant factor range of soil erosion sensitivity.[Conclusion] The distribution of RDLS in the study area was consistent with that of soil erosion with different sensitivities. Generally, soil erosion was significantly affected by the change of topographic relief.

Abstract:[Objective] The relationship between soil particle size and organic carbon under different grassland use patterns was studied, to reveal the loss rate of soil organic carbon in grassland degradation process, in order to provide a scientific basis for the restoration and control of ecological environment in Horqin sandy land.[Methods] Taking the flow and semi-fixed aeolian sandy soil in the Wulijimulun River basin of Horqin sandy land as the research object, the relationship between grain size and organic carbon content was studied under different grassland utilization modes, such as the enclosed grassland in the basin, the salinization plots with different degrees of degradation and the artificially planted pasture plots.[Results] The enclosing measures played a significant role in controlling soil erosion and increasing soil organic carbon content. In the 0-20 cm soil layer of the watershed, the grain size composition was dominated by silt and sand. Due to the factors of tillage, the surface soil in oat and alfalfa plotswas coarser, and had higher peak and median grain size than other plots. In the study area, the particles with a size around 100 μm were easily to be eroded. For the soil particles with a size less than 100 μm, the organic carbon would be lost by 0.120 4 g/kg for every 1% wind erosion.[Conclusion] The saline-alkaline meadow land distributed in the hills can be combined with the enclosure measures and planting grasses, to prevent soil erosion and effectively increase the organic carbon content.

Abstract:[Objective] The water conservation function of loess in different vegetation in the Loess depression of Zizhou County, Shaanxi Province was investigated in order to provide scientific basis for the allocation of soil and water conservation measure in this area.[Methods] This paper systematically studied the soil infiltration characteristics and its influencing factors under different vegetation of Loess Plateau, by using the field double-ring infiltration experiment and indoor soil particle size analysis.[Results] The stable infiltration rates of flat grassland, slope grassland, jujube forest land and apricot forest land in the study area were 1.91, 1.54, 1.47 and 1.56 mm/min, respectively. The stable infiltration rate of the silted corn plot from the upstream(sample plot A) to the downstream(sample plot F) plot was generally getting smaller, with a variation between 0.69 and 1.1 mm/min. Grassland and woodland had greater infiltration rates than silt corn plot. Fitting by the infiltration experience formula, the best fitting effect was the Kostiakov model, and the fitting effect of Horton model and the empirical general formula was general.[Conclusion] The soil infiltration rate of loess layer under different vegetation in the area is higher than that of the silted corn field, and the infiltration rate from the upstream to the downstream in the corn field is also gradually decreasing.

Abstract:[Objective] The adaptation strategies of Robinia pseudoacacia seedlings under drought stress were explored, in order to provide support for afforestation site selection of artificial Robinia pseudoacacia forests during vegetation restoration.[Methods]Using the potted water control experiment method, the annual seedlings were used as experimental subjects to study the adaptation mechanism of Robinia pseudoacacia seedlings. Four water gradients were respectively set as follows:75%~90%, 60%~75%, 45%~60%, and 30%~45% of soil water holding capacity.[Results] ① Moderate water stress(45%~60%) and severe water stress(30%~45%) significantly inhibited the growth of seedling, and the plant height, ground diameter and crown width were significantly lower than those of the control group(75%~90%). ② With the deepening of soil water stress, root phosphorus content, specific leaf area and specific root length decreased, while leaf thickness and leaf tissue density increased in Robinia pseudoacacia seedlings. There was no significant different between mild water stress(60%~75%) and the control group, and the growth state of mild water stress was even better than that of the control group at the end of the experiment. ③ Moderate water stress and severe water stress significantly reduced the biomass accumulation of seedlings and increased the root-shoot ratio of seedlings.[Conclusions] Robinia pseudoacacia seedlings adapts to the arid environment by investing a relatively large amount of assimilated material into the defense organization. Severe water stress inhibited the growth of seedlings seriously, while under mild water stress, seedlings could achieve maximum growth benefit.

Abstract:[Objective] A scientific and reasonable post-evaluation index system for soil and water conservation project benefits was established, in order to provide a scientific post-assessment basis for ecological management of small watersheds.[Methods] According to the comprehensive analysis of the characteristics of soil and water conservation engineering in small watersheds and the key factors affecting the efficiency of soil and water conservation projects, 13 key indicators for post-evaluation of soil and water conservation project were identified and selected, to establish a post-evaluation index system. Analytic hierarchy process(AHP) and the entropy method were used to improve the weight of the evaluation index. Combined with the evaluation index data, the index evaluation criteria was applied to improve set pair analysis model and analyze the post evaluation of project benefits.[Results] The improved set pair analysis model showed that the water conservation benefits, ecological benefits and social benefits in the evaluation index system were generally at the level of 2, and the effectiveness of watershed management was significant, and the potential for development was great.[Conclusion] The research demonstrates a new method to effectively evaluate the benefit of soil and water conservation projects in small watersheds. The new method is applied to the post-evaluation of soil and water conservation project benefit on the basis of constructing the post-evaluation index system, which basically achieves the expected research purpose.

Abstract:[Objective] Taking the Yangling Agricultural Hi-tech Industries Demonstration Zone with the surrounding water system in Shaanxi Province as the research object, this paper analyzed the relationship between the urban construction of the developing city and the ecological base flow of rivers around the city in order to provide a scientific basis for the ecological water planning of the basin and the rational allocation of river water resources.[Methods] The minimum monthly average flow method was used to calculate the ecological base flow of the rivers. The relationship between the minimum monthly average flow and urban construction area was analyzed to estimate the water warning line. And the impact of urban construction on the protection of ecological base flow was analyzed from the perspective of sediment transportation and self-purification of water.[Results] ① The ecological base flow of Weihe River, Qishui River and Xiaowei River around the Yangling Demonstration Zone was about 6.0, 0.2 and 0.1 m³/s, respectively, which could be used as the basis for the water use planning and water resources allocation for the three rivers in this area. ② The internal relationship between the minimum monthly average flow of Xiaowei River and the construction area of Yangling Demonstration Zone was exponential. The warning value of urban construction area was 60 km² to ensure the ecological base flow of Xiaowei River. ③ The monthly average concentration of total nitrogen and total phosphorus of Xiaowei River exceeded the V-class water quality standard. The current situation of high pollution in winter and spring made it more severe and urgent to guarantee the ecological base flow of Xiaowei River.[Conclusion] The urban construction of Yangling Demonstration Zone is closely related to the ecological base flow of rivers around the city, especially Xiaowei River. Sponge city construction is an important development direction for the developing cities in the future.

Abstract:[Objective] The relationship between biological measures and their influence factors on soil erosion on steep slopes were studied, in order to provide theoretical basis for gully control and vegetation measure allocation of soil and water conservation.[Methods] Two slope gradients and seven herb vegetation models were set up by small plots, and runoffs and soil losses of the plots were monitored from June to September in 2018.[Results] Compared to bare plot, the average runoff at 1:1.5 and 1:1.2 ratio slope with herb vegetation was declined by 27% and 26%, and the average soil loss reduced by 52% and 21%, respectively. As the slope steepness increased from 34° to 40°, runoff didn't show significant increase, but the amount of soil loss increased markedly. The dominant rainfall factors influencing runoff and sediment were precipitation, I₃₀, E and EI₃₀. The correlations among runoff, sediment and rainfall increased with the increase of slope steepness. The mixture of Bromus inermis and Medicago sativa L had the best effect on reducing runoff and sediment. The soil erosion control effect of mixed sowing of Bromus inermis, Medicago sativa L and Poa annua L was better than that of single sowing. With the increase of vegetation coverage, the sediment reduction effect of 1:1.2 slope was gradually enhanced, and when the vegetation coverage was more than 50%, the effect of sediment reduction was close to 1:1.5 slope.[Conclusion] Under the mixed herb configuration of Bromus inermis and Medicago sativa L. the 1:1.2 ratio slope could be used for gully erosion control, which could save 20% of the gully slope cutting area.

Abstract:[Objective] The effects of microorganisms and algae on the recovery of biocrusts in the field were studied and the biocrusts protection technology of high and steep loess slopes was optimized in order to provide new ideas and methods for regional ecological restoration.[Methods] The effects of algae(chlorella+diatom mixed algae) and functional microorganisms(Bacillus licheniformis, Bacillus megaterium) on the development of artificially restored biocrusts were studied by complete experiments.[Results] ① There were significant difference in development among different treatments, the median biocrust coverage of algae+Bacillus megaterium was the largest, with a mean value of 61.41%; the median biocrust thickness of Bacillus licheniformis was the largest, with a mean value of 2.58 mm; the median height of moss plant treated with only 3 g algae was the highest, with a mean value of 2.67 mm. ② Algae treatment could explained the difference of biocrusts coverage, thickness and plant height among different sample squares significantly(p<0.05) under different addition levels (0,1 or 3 g/m²), and the suitable addition amount was 2~3 g/m². ③ The functional microorganisms showed little effects on the biocrusts coverage, thickness and plant height of moss (p=0.91/0.93/0.49) and it showed no significant interaction with algae.[Conclusion] Artificial restoration of biocrusts on 45° slope is feasible. Spraying the algae solution on the slope with suitable environment, inoculating the gametophytic fragments of moss and carrying out the restoration of the biocrusts, can effectively construct a well-developed biocrusts protective layer with a certain coverage and thickness.

Abstract:[Objective] The improvement effect of different tillage modes on the newcultivated land with raw soil as construction material was explored in order to provide scientific basis for high-yield and efficient utilization of this kind of land.[Methods] During the period from June to September in 2017, a location monitoring experiment was conducted in maize fields under three tillage modes of no-tillage, subsoiling and plowing, respectively. And the effects of tillage modes on soil compactness, nutrient content and crop yield were analyzed.[Results] The compactness of 0-20 cm soil layer was the lowest under the no-tillage mode, which was 37.49 and 38.48 kPa/cm² lower than that of subsoiling and plowing, respectively. And the compactness of 0-20 cm soil layer in each mode presented a stratified state. The soil compactness was the lowest at maize seedling stage and the highest at bell stage. The contents of organic matter, total nitrogen and available phosphorus in the 0-40 cm soil layer were the highest in the subsoiling mode, which were 1.20, 1.22, 1.36 times of no-tillage mode, and 1.18, 1.08, 1.34 times of plowing mode, respectively. The content of available potassium in subsoiling and plowing was similar, which was 1.09 times of that in no-tillage. From the seedling stage to the filling stage, the content of organic matter and total nitrogen increased, while the content of available phosphorus and available potassium decreased. The maize yield under subsoiling mode was the highest, which were 1.30 and 1.19 times of that under no-tillage and plowing, respectively.[Conclusion] The soil compactness of subsoiling mode is moderate, which can effectively increase the soil nutrient content and crop yield. It is the most ideal tillage and improvement method for the new cultivated land.

Abstract:[Objective] The comprehensive evaluation of soil nutrient geochemistry in Guanzhong region of Shaanxi Province was studied, to provide scientific basis for land quality, ecological management and rational utilization of land resources.[Methods] Based on 12 evaluation indexes such as mass nutrients, medium nutrients, and trace nutrients in the geochemical survey of land quality, a multi-level fuzzy comprehensive evaluation model based on entropy weight was constructed. The entropy theory was used to determine the weight. The grades were vaguely evaluated by multiple levels, to divide the differences among the evaluation indicators in Guanzhong area.[Results] The proportion of first and second class of mass nutrients accounted for 2.0%. The proportion of first and second class of medium nutrients accounted for 30.31%. The proportion of first and second class of trace nutrient accounted for 66.42%. The proportion of first and second class of soil nutrient geochemistry accounted for 33.52%. The mass nutrients, medium nutrients, and trace nutrients were all lack in the valley area. The medium nutrients and trace nutrients were rich in Weibei plateau, but the mass nutrients was lack. The mass nutrients, medium nutrients, and trace nutrients were rich in the middle and low mountains. The trace nutrients was rich in the northern edge of the Qinling Mountains, and the mass nutrients were at a moderate level, while the trace nutrients were lacking.[Conclusion] The mass nutrients is lacking, while the medium nutrients and trace nutrients are rich in Guanzhong area. The comprehensive evaluation level of soil nutrients is mainly the second, third and fourth level, but the spatial variation is large. To improve the soil productivity in Guanzhong area, it is necessary to apply the fertilizer of mass nutrients as a whole, and at the same time, to apply the medium nutrients and trace nutrients in different landscape areas.

Abstract:[Objective] Based on the man-grain relationship, the spatio-temporal variation characteristics of land resources carrying capacity from 2000 to 2015 in Ordos City were studied by land resources carrying capacity model, in order to provide theoretical basis for the sustainable development of the economy and society in the fieldspathic sandstone area.[Methods] Landsat images of 2000, 2005, 2010 and 2015 were used to extract land use types in fieldspathic sandstone area. Social and economic data such as land area, grain yield and population was used. Spatio-temporal variation characteristics of land resources carrying capacity were then studied by using land resources carrying capacity model and index in Ordos fieldspathic sandstone area.[Results] ① From 2000 to 2015, the carrying capacity of land resources in Ordos shows a gradual increase trend, and the carrying capacity index of land resources fluctuated and decreased. ② Grain output showed a gradual increase trend. Man-grain relationship was basically in the state of grain surplus, and the population carrying capacity still had a certain growth space. ③ There were great differences in the carrying capacity of land resources among different districts in Ordos City. The carrying capacity of land resources in Dongsheng District and Jungar Banner was relatively higher, and the contradiction between population and grain was serious. The carrying capacity of land resources in Etok Banner and Ejin Horo Banner was medium, and the state of grain surplus existed in most years from 2000 to 2015. Etok Qian Banner, Hangjin Banner, Uxin Banner and Dalad Banner were in the state of grain surplus, and the carrying capacities of land resources were relatively lower.[Conclusion] There is still room for the carrying capacity of land resources growth in Ordos fieldspathic sandstone area, but there are great differences among different banners or districts.

Abstract:[Objective] The distribution characteristics of soil pressure on purple soil sloping farmlands bunds and its influencing factors were studied in order to provide basis for the optimal design, construction and maintenance of the purple soil sloping farmland bunds in the Three Gorges reservoir area and the upper reaches of the Yangtze River.[Methods] Using soil bin simulation test, water was injected into the soil bin until the soil was basically saturated. Soil pressure was determined by static strain gauge, and soil moisture content was measured by drying method to analyze the variation characteristics of soil pressure under water attenuation.[Results] ① The soil pressure presented a nonlinear distribution with the increase of soil depth, which showed that the soil pressure initially increased with the increase of soil depth, reached the maximum at about 0.375 H from the bottom of the test device, and subsequently decreased with the increasing soil depth. ② Under the experimental conditions, the change of soil moisture content presented an approximate linear attenuation with time, and had a significant impact on the soil pressure(p<0.01), but there were some differences among different soil layers. ③ The interaction effect of soil depth and soil moisture content on soil pressure was significant(p<0.01).[Conclusion] The distribution of soil pressure show a non-linear trend on purple-soil sloping farmlands bunds in the Three Gorges reservoir area, the soil depth, soil moisture content and their interactive effects have significant effects on the soil pressure.

Abstract:[Objective] This paper studies the land use change in Fuzhou New District of Fujian Province from 2000 to 2015, forecasts the land use pattern in 2030, analyzes the habitat quality change in 2000-2030, and compares the predicted results with the overall planning of the new district, in order to provide a reference for the rational use of land resources in the later stage of the new district.[Methods] Taking Fuzhou New District of Fujian Province as an example, based on the data of land use in 2000 and 2015, which was interpreted by Landsat_ETM⁺ and Landsat_OLI remote sensing image, the spatial analysis model of land use change was used to analyze the dynamic change of land use in Fuzhou New District, and the CA-Markov model was used to predict the land use pattern in 2030. On this basis, the past, present and future habitat qualities in the new district were further evaluated by the InVEST model.[Results] ① During 2000-2015, the cultivated land, forest land, water area and construction land in Fuzhou New District changed rapidly, the change of grassland and sea area was relatively small, and the change of unused land area was relatively small, but the transfer in and out was more intense; ② CA-Markov model prediction showed that the change trend of land use in the study area in 2015-2030 was basically the same as that in 2000-2015. In addition to the increasing trend of unused land, the construction land and ecological land showed the trend of rapid expansion and continuous reduction respectively; ③ From 2000 to 2030, a large number of cultivated land, forest land, grassland and water area in the study area transformed into construction land, resulting in the increase of threat sources and further reducing the habitat quality.[Conclusion] Due to the rapid expansion of construction land in Fuzhou New District, the quality of habitat in the area is seriously reduced. We should strengthen ecological conservation, reasonably control the growth of construction land, and avoid the further deterioration of habitat quality. The boundary of construction land in 2030 land use planning should be taken as the boundary of restricted construction area, and the predicted result should be taken as the boundary of permitted construction area, so as to improve the intensive utilization of construction land.

Abstract:[Objective] The quality survey and pollution assessment of shallow groundwater was conducted in Chengdu plain in order to provide theoretical basis for soil and groundwater resources protection and the rational development and utilization of groundwater resources in this region.[Methods] Sixty shallow groundwater samples were collected in the typical sample area of Chengdu plain, and 11 indicators including the pH value, total dissolved solids, total hardness, chloride, ammonia nitrogen, fluoride, nitrate, nitrite, sulfate, iron and manganese were analyzed. The groundwater quality in the study area was evaluated by the hierarchical ladder evaluation method and principal component analysis method (PCA). And the comprehensive evaluation map of water quality was drawn by MapGIS.[Results] Some indicators of shallow groundwater in the study area exceeded the standard, especially nitrate pollution, followed by total hardness, iron and manganese.[Conclusion] The groundwater quality in the study area is generally good, except for a certain degree of pollution in some areas.

Abstract:[Objective] The multi-level collapsibility of loess was investigated and the way of loess collapsibility deformation was studied at the microscale in order to provide a scientific basis for the study of loess collapsible deformation mechanism.[Methods] We designed and conducted a indoor cyclic collapsibility test, to observe the micro-structure of the same samples under repeated humidification and dehumidification processes. The collapsibility data were analyzed and the scanning electron microscopy images were compared.[Results] The collapsibility data showed that after the loess reached the first collapsibility and water removal stability, adding water into the device would cause the deformation of the sample again. During the collapsibility process, the micro-structure undergone three deformation modes:dissolution, movement and reconstruction.[Conclusion] It is the dynamic process of destruction-reconstruction-destruction of loess structure that leads to multi-level collapsibility of loess.

Abstract:[Objective] The susceptibility of geological disaster was evaluated, in order to provide a theoretical basis for geological disaster prevention in Luding County, Sichuan Province.[Methods] With the help of Google image interpretation, 279 potential geological disaster points such as collapse, landslides and debris flows were obtained. The evaluation index system was constructed from four aspects including topography, lithologic structure, meteorological hydrology, soil and land use(LULC). The weight of the factors is determined by the deterministic coefficient method, and the weighted information model was constructed by the information quantity method. Disaster vulnerability was assessed by the ArcGIS spatial analysis.[Results] The extremely high and high risk areas accounted for 13.54% and 26.49% of the total study area, respectively. A total of 225 geological disaster sites were located in the extremely high and high risk areas, accounting for 80.65% of the total sample disaster points. The test was performed by the offline area(AUC) of the receiver operating characteristic curve(ROC), and its value was 0.793, and the accuracy of the evaluation model was excellent.[Conclusion] The geological disasters in Luding County was classified, and the risk assessment results of the weighted information method were reliable.

Abstract:[Objective] The characteristics of precipitation change and multi-time scale characteristics of drought and flood in the farming-grazing transitional zone of South China was studied in order to provide scientific reference for the decision-making of drought and flood disaster prevention and control, ecological reconstruction and protection in the pastoral area.[Methods] Based on monthly precipitation data of 20 meteorological stations in the farming-grazing transitional zone of South China from 1960 to 2017, the precipitation characteristics, spatial and temporal patterns of drought and flood disasters were studied by using standardized precipitation index (SPI), Inverse Distance Weight Interpolation and M-K mutation test in the farming-grazing transitional zone of South China in recent 58 years.[Results] ① The annual average precipitation in the farming-grazing transitional zone of South China increased at a rate of 3.98 mm/10 a in the past 58 years, precipitation was mainly concentrated in summer. Detected by M-K method, the abrupt change of annual average precipitation was occurred in 1990. ② Due to the influence of climate,atmospheric circulation, topography, altitude, underlying surface and other factors, the spatial distribution of precipitation was bounded by Vici-Litang-Ruoergai, with less precipitation in the northwest and more in the southeast, showed a decreasing trend from southeast to northwest. ③ The annual precipitation in the study area was bounded by Songpan-Malkang-Xinlong-Litang-Daocheng line. The annual precipitation in the east of the line showed a more significant growth trend, while the annual precipitation in the west showed a more significant decrease trend.[Conclusion] In the study area, the frequency of drought was slightly higher in the 1960s-1970s, and the frequency of flooding was higher in the 1980s-1990s. Since 2000, the drought and flood disasters have been weakened obviously.

Abstract:[Objective] Taking Nanchong City of Sichuan Province as an example, the benefits of targeted poverty alleviation in underdeveloped areas were studied in order to provide scientific basis for regional poverty alleviation decision-making and socio-economic development.[Methods] Based on the targeted poverty alleviation in Nanchong City, a evaluation index system of targeted poverty alleviation was established from four dimensions of economic development, social progress, ecological protection and self-development. The AHP method was used to evaluate the benefits of targeted poverty alleviation in Nanchong from 2011 to 2016.[Results] ① The economic development benefits experienced a process of first reducing and then increasing. There was a decline trend during the period from 2011 to 2012, and the decrease rate was 20.8%. ② The social progress benefits showed a downward and upward trend, and it was reduced from 0.585 1 in 2011 to 0.404 0 in 2012. From 2015 to 2016, it was gradually increased. ③ The ecological protection benefits increased year by year, but the fluctuations decreased from 2012 to 2013, which was higher than the added value of economic development benefits and social progress benefits during the same period. ④ Self-development benefits showed an alternate process of increase and decrease, and the comprehensive benefit increased year by year from 2011 to 2016, although there were fluctuations in 2013.[Conclusion] Since the implementation of targeted poverty alleviation, Nanchong City has achieved remarkable economic development benefits, social progress benefits, ecological protection benefits, and self-development benefits.

Abstract:[Objective] Based on the protection of landscape ecological security, this paper put forward the development strategy of construction land division in order to provide scientific basis for alleviating the contradiction between man and land, coordinating the sustainable development of economic and social ecology, and implementing the strategy of rural revitalization.[Methods] Taking Yongtai County, Fujian Province as an example, GIS spatial analysis and the theory of landscape security pattern was used, to select the main resistance factors from landform and landscape of land use types. The landscape ecologic security pattern with different security levels was constructed, and the comprehensive scores of ecological security of different villages and towns were obtained. In addition, principal component analysis method was used, township was taken as the evaluation unit, and the appropriate evaluation factors were selected to obtain the demand ability scores of economic development of different towns and villages.[Results] Considering the score of ecological security pattern and economic development demand, the land in the study area could be divided into four types of construction and development areas:priority, mode ration, control and prohibition. And the development direction and strategy of construction land was proposed.[Conclusion] The concept based on the construction of landscape ecological security pattern, makes up the defect of traditional spatial development layout, which only considers economic development while ignores ecological protection. This concept can be widely used in ecological protection, spatial planning control and the prevention of disordered spread of construction land.

Abstract:[Objective] The spatial distribution pattern of soil conservation service function in Shanxi Province was analyzed, and the key areas that need to be protected were identified, in order to provide reference for ecological protection redline delineation and national territorial planning.[Methods] The revised universal soil and water loss equation(RUSLE) was used to analyze the importance of soil conservation function.[Results] The total amount of soil conservation was 6.52×10⁹ t/a, and the average amount of soil conservation per unit area was 416.10 t/(hm²·a) during the study period. The spatial distribution pattern of the ecosystem's soil conservation function was low in northwest and high in southeast, as well as low in basin and high in hills and mountains. The areas of extremely important areas, important areas and general important areas accounted for 23.10%, 28.33% and 48.57% of the total area of Shanxi Province, respectively.[Conclusion] The extremely important areas of soil conservation function in Shanxi Province were mainly distributed in Taihang Mountain, Luliang Mountain, Heng Mountain, Wutai Mountain, Taiyue Mountain and Zhongtiao Mountain, and it was also widely distributed in loess hill area of western Shanxi Province.

Abstract:[Objective] The source characteristics of nitrate pollution in the high and low water period of Fenhe River were analyzed and studied in order to provide theoretical support for the treatment of nitrogen pollution in the lower reaches of the Fenhe River.[Methods] The changes of nitrate and its nitrogen and oxygen isotopes in different periods in the lower reaches of Fenhe River in 2018 was analyzed to investigate the characteristics of the change of nitrate sources discharged into the river in rainy periods. And the Isosoure model was introduced to calculate the contribution of each pollution source to the nitrate in the lower reaches of Fenhe River.[Results] In the high and low water period, the variation range of δ¹⁵N was 3.45‰~11.19‰, δ¹⁸O value was -0.72‰~3.17‰. The nitrate pollution sources were mainly agricultural fertilizer, soil organic nitrogen, domestic sewage and feces. The nitrate pollution sources were mainly related to the land use types around the lower reaches of Fenhe River. In the high water period, the nitrate pollution sources at Linfen section and M₅ sampling point were mainly feces and sewage, accounting for 58%, 40%, 72% and 58%, respectively. The contribution rate of agricultural fertilizer in M₆-M₉ section was the highest, accounting for 45.4%, 62%, 56.6% and 56.5%, respectively. The highest contribution rate of nitrate pollution sources in all sampling points in low water period was feces and sewage, accounting for 40%~73%.[Conclusion] The main sources of nitrate pollution in the runoff of Fenhe River are agricultural fertilizer, soil organic nitrogen, domestic sewage and feces, and the pollution sources are closely related to land use types. Most of the sources of nitrate pollution in different water periods are feces and domestic sewage, and the difference is mainly reflected in the M₆-M₉ sampling point. The main pollutants in the wet period are agricultural fertilizer, while in the dry period are feces and domestic sewage.

Abstract:[Objective] The influencing factors of water environment change and its improvement countermeasures in Danjiangkou reservoir area after the operation of the middle route of south-to-north water diversion project were studied in order to provide reference for reducing pollution load and ensuring water quality safety in the reservoir area.[Methods] Taking Danjiangkou reservoir and the upper reaches of the river basin as the study area, the characteristics of water environment change and its main influencing factors were analyzed by using the before and after comparison methods, and the countermeasures to protect and improve water environment were proposed.[Results] After impoundment of the dam, the water quality of Danjiang Reservoir area was generally good, but the spatial difference was significant. Some tributaries and bays were polluted seriously, and the contents of nitrogen, phosphorus and some heavy metals were high.[Conclusion] Soil and water loss, point source pollution in rural areas, non-point source pollution in agriculture and human activities are the main factors affecting water quality in Danjiangkou reservoir area. In view of the ecological environment problems existing in the reservoir area, the protection countermeasures and suggestions are proposed, such as continuous and stable implementation of the policy of returning farmland to forest or grassland, the optimization of the rural industrial structure, the strengthening of the supervision of industrial and mining enterprises' pollution discharge, the optimization of monitoring stations and the strengthenomg the residents' environmental protection awareness.

Abstract:[Objective] The land use/cover change(LUCC) and the response of ecosystem service value(ESV) in the Ulungu River basin in the past 30 years were investigaged in order to provide scientific basis for guiding the optimal allocation of soil and water resources in this region.[Methods] The Landsat series of remote sensing images in 1989, 1998, 2006, and 2017 were selected, and the 3S technology was comprehensively used, to monitor and analyze the temporal and spatial evolution characteristics of LUCC in the study area in the past 30 years. The modified ESV equivalence factor was adopted to calculate and analyze the ESV response.[Results] ① In the past 30 years, the area of cultivated land and construction land in the Ulungur River basin had showed a trend of continuous increase and expansion. The area of water bodies and wetlands had showed a trend of slight increase, the area of the unused land had showed a trend of significant decrease, the area of forest land had showed a trend of increase with fluctuation, and the grassland area had showed a trend of decrease in 1989-2006 and a trend of slight increase in 2006-2017. Among them, the net increase of cultivated land was the largest(847 km²), while the net decrease of unused land was the largest(744 km²). The regions with the most significant land use type transfer were mainly located in Fuhai County, Dure Village, and Qiganjidi Village. ② The comprehensive land use index of the Ulungur River basin increased from 146.75 in 1989 to 168.29 in 2017. The ESV increased from 0.263 5 billion in 1989 to 0.291 5 billion in 2017, with a net increase of 28 million yuan.[Conclusion] The area of different land use types of the Ulungur River basin has changed and transformed in different degrees in the past 30 years. The land resources in the study area are in the period of high-intensity development. The ESV responds correspondingly, and the total ESV increases.

Abstract:[Objective] The spatial and temporal evolution of ecological security in Guanzhong plain urban agglomeration was studied in order to provide scientific reference for the formulation of ecological security measures in this area.[Methods] The social economy-natural ecology lotka-volterra symbiosis model and the DPSIR indicator system of ecological security were constructed to measure the ecological security status of Guanzhong plain urban agglomeration from 2008 to 2017. And the causes of ecological security problems were analyzed based on the measurement results.[Results] ① From 2008 to 2017, the social and economic development of Guanzhong plain was rapid, but the improvement of ecological environment was not obvious. ② From 2009 to 2016, the force direction of social and economic subsystems was positive, while that of the natural ecological subsystem was negative in many years, which indicated that the profit-oriented development model with rapid social and economic development and the damage of ecological environment existed for a long time in Guanzhong plain urban agglomeration.[Conclusion] Factors such as the slow pace of industrial structure optimization, industrial pollution, pressure on ecological carrying capacity caused by population expansion, and the occupation of rapid urbanization on natural resources have become important reasons that hinder the improvement of ecological security in Guanzhong plain urban agglomeration.

Abstract:[Objective] The coordination relationship between intensive land utilization and land use structure was explored in order to provide theoretical basis for the optimization of land use structure and sustainable development of social economy in Qingyang City, Gansu Province.[Methods] Taking Qingyang City as an example, the comprehensive index of intensive land utilization and land use structure from 2007 to 2016 was calculated by multi-factor comprehensive evaluation method. The coupling coordination model was used to analyze the change characteristics and coupling coordination relationship between land intensive utilization and land use structure.[Results] ① The comprehensive index of land intensive utilization showed an increase trend, and reached a high level of intensive utilization in Qingyang City. ② The information entropy of land use structure showed a downward trend, the equilibrium was gradually decreasing, and the advantage was gradually increasing in Qingyang City. ③ The coupling degree of land intensive utilization and land use structure increased initially and then decreased, and the coupling coordination showed an increasing trend. The coupling between the two was becoming stronger and stronger, and showed a coordinated and stable trend.[Conclusion] By studying the relationship between land intensive utilization and land use structure, it is found that the unit input to promote the level of land intensive use in Qingyang City is no longer applicable, and the land use structure need to be changed in order to further improve the efficiency of land use and promote the level of land intensive use.

Abstract:[Objective] The changes of land use pattern in the Yaoluoping National Nature Reserve from 1994 to 2017 were analyzed, and the impacts of returning farmland to forests and ecotourism on the change of land pattern were revealed in order to provide a basis for the protection and utilization of forestland in the nature reserve.[Methods] Land use information was extracted from four LandsatTM/ETM⁺/OLI images from the years of 1994, 2002, 2012 and 2017. By use of supervise classification and transition matrix, the dynamic changes of land use pattern and its transfer characteristics in the nature reserve were analyzed during the past 20 years.[Results] The results showed that the land use structure in the nature reserve changed dramatically from 1994 to 2017. The forest land, residential areas and gardens increased, while the cultivated land decreased significantly. The main change was that cultivated land converted into gardens and residential areas, and a small part of forest land was transformed into residential areas. From 1994 to 2002, the area of forest land increased greatly, and the cultivated land decreased greatly. From 2002 to 2012, the residential area showed a trend of expansion, the area of garden increased greatly, while the cultivated land decreased. The amount of land use conversion was relatively small during the period from 2012 to 2017, the area of residential land, woodland and garden increased slightly, and the area of cultivated land reduced relatively.[Conclusion] The change of land use pattern in the Yaoluoping National Nature Reserve is the result of returning farmland to forests, tea industry and tourism development. Returning farmland to forests has resulted in the reduction of farmland and the increase of forest land, and the tourism development has resulted the increase of residential land.

Abstract:[Objective] Taking the Pearl River-Xijiang River economic zone as an example, this paper analyzed the change of ecosystem pattern and evaluated its ecosystem service value in the typical east-west junction area, in order to provide a scientific basis for the construction of the regional ecological security pattern and ecological compensation research.[Methods] Based on the data of ecosystem types in the Pearl River-Xijiang River economic zone from 2000 to 2015, the change characteristics of ecosystem pattern were studied by using the annual average change rate and the transfer matrix of ecosystem types. The ecosystem service value in the research area was evaluated and analyzed in the past 15 years.[Results] ① During 2000-2015, the Pearl River-Xijiang River economic zone was dominated by forest and farmland ecosystems, and the spatial distribution pattern of ecosystems was relatively stable. The changes were mainly the expansion of the eastern artificial surface ecosystem. ② The area of farmland and grassland ecosystems decreased the most, while the wetland decreased least, and the area of the other ecosystem types increased in varying degrees. The conversion of ecosystem types mainly occurred between forest, farmland and artificial surface ecosystems. ③ From 2000 to 2015, the ecosystem service value in the Pearl River-Xijiang River Economic Zone decreased by 1.455 billion RMB, of which the value of grassland ecosystem service declined the most, while the value of forest ecosystem service increased the most. ④ The spatial distribution pattern of ecosystem service value in the counties and the districts of the Pearl River-Xijiang River economic zone was stable, but the ecosystem service value of per unit area in the eastern region showed a continuous decline trend.[Conclusion] The changes in the ecosystem pattern in the eastern part of the Pearl River-Xijiang River economic zone from 2000 to 2015 had a great impact on the decline of its ecosystem service value. In the future, it is necessary to control the expansion rate of the area of the artificial surface ecosystem in the east, to prevent the continuous decline of ecological service value.

Abstract:[Objective] The transfer characteristics of land use types and its impact on the thermal environment in the process of urbanization were studied, in order to provide scientific basis for optimizing the land use pattern and regional development and management in the context of low carbon.[Methods] Take Haiyan County, Zhejiang Province as a case study area, based on the four Landsat satellite images, the county-level land use types were interpreted and surface temperatures were derived. The spatial and temporal distribution of urban heat islands and the impact of land use type transfer on the thermal environment were analyzed by the land use transfer matrix and the contribution index of thermal effect.[Results] From 2007 to 2017, the built-up area in the central urban area of Haiyan County expanded significantly, the pattern of land use also changed significantly, and the dynamic degree of land use reached to 42.3%. The urban land area increased significantly, with a transfer rate of 44.1%, mainly transferred from vegetation and roads. The vegetation coverage area decreased significantly, and the transfer rate was 51.2%, mainly transferred into urban land and roads. The distribution of urban heat island was gradually dispersed from the concentrated island to the edge of urban area. With the increase of urban area, its thermal contribution increased from 59.6% in 2007 to 87.5% in 2017.[Conclusion] Urban land use is a decisive factor affecting the thermal environment of Haiyan County. In the process of urbanization, reasonable and effective planning and control of the expansion of built-up areas is important measures to slow down the heat island effect.

Abstract:[Objective] The decoupling relationship between regional economic growth and land resource utilization in Beibu Gulf economic zone of Guangxi Zhuang Autonomous Region was analyzed to reveal the spatial evolution law of the decoupling degree, in order to provide a scientific basis for the coordinated development of regional economic growth and land resource utilization.[Methods] The Tapio decoupling model was used to quantitatively evaluate and comprehensively analyze the decoupling degree and the spatial-temporal evolution of land resource utilization and economic growth in the economic zone from 2007 to 2016.[Results] The land use and economic growth in Beibu Gulf economic zone were basically in a state of decoupled, and there was a trend from weak decoupling to strong decoupling. From the perspective of industrial type, the primary industry GDP and cultivated land were mainly strong decoupling and accompanied by weak decoupling and expansion coupling. The primary industry GDP and forest land were mainly weak decoupling and showed a trend from weak to strong decoupling. The second and third Industry GDP were always in a weak decoupling state with the construction land.[Conclusion] To realize the sustainable decoupling of land use and economic growth in Beibu Gulf economic zone, we should not only continue to optimize the industrial structure, but also focus on the optimization of land space from the perspective of global and regional coordination development, and comprehensively build ecological space, achieve the coordinated development of economic growth and land use by improving the comprehensive development capacity of marine resources.

Abstract:[Objective] The ecosystem health of Gahai wetland of South Gansu Province was comprehensively evaluated in order to provide a scientific basis for the management and sustainable development of the wetland.[Methods] Using PSR mathematical model, 18 evaluation indexes were selected from three aspects including pressure, state and response, to construct the health evaluation system of Gahai wetland. Analytic Hierarchy Process (AHP) was used to determine the weight of indicators and to analyze the ecosystem health index.[Results] The health index of the Gahai wetland ecosystem was 0.588 1, which belonged to the sub-health state, and the health index of the pressure subsystem was 0.733 2, which belonged to the health state. The health indexes of the state and the response subsystem were 0.489 3 and 0.567 9, respectively, both of which belonged to sub-health states.[Conclusion] Global climate change and human disturbance have seriously threatened the health of the wetland ecosystem in Gahai. wetland Scientific protection and restoration measures are urgently needed to improve the level of wetland management.

Abstract:[Objective] The field investigation of soil erosion was carried out in mountain and hilly regions of the Republic of Rwanda to analyze the characteristics and reasons of soil erosion, in order to provide basis for soil erosion prediction and control in the mountainous and hilly areas of the upper reaches of the Nile River.[Methods] Four investigation routes were selected, soil erosion characteristics and reasons, and soil and water conservation measures were investigated from October 17 to 22, 2019 in Rwanda.[Results] The Republic of Rwanda is mountainous and dominated by agriculture and animal husbandry. Soil erosion mainly occurs in slope farmland, deforested land and construction land. Slope farmland is dominated by sheet erosion and ditch erosion. Destroyed land is dominated by sheet erosion and gully erosion, and part of it appears gully erosion. When grass or young forest is formed on bare ground, soil erosion is less likely to occur. Gully erosion is caused by rainfall and runoff on roadside slope, excavated slopes and dirt road surface and slopes. Gravity erosion occasionally occurs on some roadside slopes. To prevent soil erosion, terrace is the most important soil and water conservation measure with significant ecological and economic benefits.[Conclusion] Soil erosion in Rwanda is dominated by water erosion, followed by gravity erosion. Unreasonable reclamation of sloping land, deforestation, and mountainous topography have caused severe soil erosion, and threatened food security as well as the safe ecology. Rwanda lacks monitoring data on soil and water loss at present. Thus, it is urgent and necessary to attach importance to the basic theoretical research of soil and water conservation, to strength the monitoring and collection of basic data of soil and water loss, to promote the implementation of soil and water conservation measures and land management, and to ensure the sustainable and green development of agriculture in Rwanda.

Abstract:[Objective] The approaches to improve the ecological service of soil and water conservation in the red soil hilly region of the South China were reviewed and discussed in order to provide scientific reference for the ecological construction of soil and water conservation, poverty alleviation, and sustainable development of social economy in this area.[Methods] Taking Tangbei River watershed in Xingguo County of Jiangxi Province as a case study, based on the relevant scientific research literatures, and considering the relationship between different ecological service functions, the key technology research focusing on the improvement of soil and water conservation service function was carried out.[Results]Although remarkable achievements has been made in the comprehensive control of soil erosion, Tangbei River watershed is still faced with serious soil erosion problems, such as collapse erosion, serious soil erosion under forest, soil erosion caused by large-scale economic fruit forest development, and fragile ecosystems. It was urgent to shift the focus from the prevention of soil erosion to the improvement of ecosystem services.[Conclusion] The key technologies for the promotion of soil and water conservation ecological services (such as the relationship between the balance and coordination of soil and water conservation and biological diversity, water conservation and carbon sequestration) should be developed based on the basic scientific issue such as the trade-offs and synergies among different ecosystem services and spatial mobility of soil and water conservation services. The comprehensive model for harmonious development of ecology and social economy should be constructed, and a "upgraded version" and "expanded version" of Tangbei River watershed should be built, in order to promote the transformation and application of research results, and serve the protection and construction of local ecological environment, as well as sustainable and high quality development of the red soil hilly region in the South China.

Abstract:[Objective] The achievements after the implementation of grain for green (GFG) project on the Loess Plateau for 20 years were summarized to provid references for ecological protection and high quality development in the Yellow River basin in new era.[Methods] Based on years of research results, combined with recent surveys and some documents, some new issues during GFG project implement were analyzed.[Results] The issues which should be considered at present include:how to accelerate the grassland construction; whether to carry on strict rotational grazing; how to deal with the ecological and economic forest proportion; how to continually improve the grain yield per unit area.[Conclusion] It is necessary in the new era, to lay emphasis on the study and analysis of the emerging issues during ecological construction, and seek practical solutions, so as to promote ecological civilization construction and rural revitalization in the Loess Plateau region.

Abstract:[Objective] The experiences of soil and water conservation on Loess Plateau during the past 70 years (1949-2019) after the founding of the People's Republic of China were summarized in order to provide reference for the ecological environment protection and high-quality development in this region.[Methods] Based on long-term field investigation experiences and scientific research achievements, a large number of documents and literature related to soil and water conservation work on the Loess Plateau were analyzed.[Results] In term of the main objectives and measures of soil and water conservation, the history of soil and water conservation on the Loess Plateau in the past 70 was divided into three stages:disaster prevention (1949-1980), comprehensive control (1980-2000), and ecological restoration (after 2000). Soil and water conservation in the new period should pay attention to the following aspects. ① To understand the overall reality of soil and water loss, and conservation status scientifically and rationally in the Loess Plateau; ② To raise the socio-economic and production level of the areas and improve people's living conditions. ③ To pay more attention to the environmental impacts of large-scale projects for soil and water conservation. ④ To have more scientific research projects focused on the new problems and challenges under higher-level control conditions.[Conclusion] After 70 years of soil and water conservation, remarkable achievements on the loess plateau has been achieved, including vegetation restoration and reconstruction, soil and water conservation infrastructure construction, slope soil erosion control, and sediment reduction of Yellow River. But it is very important to realize clearly that Loess Plateau still faces many severe challenges caused by many natural and human activities. Therefore, the task of soil erosion prevention and control is still arduous. It is necessary to improve the speed and quality of soil erosion control and social and economic development on Loess Plateau for making great contribution to the national strategic goals of Yellow River basin ecological protection and high-quality development.

Abstract:[Objective] The causes of soil erosion in various regions in China were discussed in order to provide theoretical basis for researches on soil and water conservation, and to enlighten young researchers in the academic research.[Methods] According to a large number of field investigations and academic exchanges, using information from various sources, the issues in soil and water conservation were analyzed mainly from the view of geology.[Results] Brief description of new opinions on five soil erosion issues:the relationship between the feldspathic sandstone in the contiguous area of Shanxi Province-Shaanxi Province-Inner Mongolia and the oil and gas fields and the uranium deposits in the Ordos Platform; preferential flow and its effects on the gully formation and groundwater recharge in the tableland of Loess Plateau; collapsed gully erosion and its control in South China; influences of the underlying mild clay on erosion of the black soil in Northeast China; and soil leaking on karst slops in Southwest China.[Conclusion] The science of soil and water conservation is an applied subject closely combined with practices, and should firstly serve for the needs of national ecological civilization construction. Researchers should be good at discovering problems, dare to doubt authorities, and solve the problems with comprehensive and multidisciplinary knowledge. Only in this way can we ensure that our scientific researches continues to progress in the right direction.

Abstract:[Objective] The landscape change of Mu Us sandy land in the past 100 years was analyzed in order to provide basis for the study of ecological management in this area.[Methods] Through satellite image interpretation and field investigation, we found out the shooting site of four photos taken by Robert Sterling Clark expedition in the Mu Us sandy land in 1908, and rephotographed the photos of the past hundred years in 2019, and then compared the changes of ecological factors in the new and old photos.[Results] More than one hundred years ago, Mu Us sandy land was sparsely covered with vegetation, and the sandstorm was rampant. After the founding of the People's Republic of China, the local government organized the masses to carry out sand remediation. After decades of treatments, mobile sand dunes were fixed, regional vegetation was effectively restored, and soil erosion was effectively controlled.[Conclusion] Due to the fragile ecology of Mu Us sandy land, there is still the risk of desertification in the sand land that has been treated. It is necessary to integrate the treatment of Mu Us sandy land into the overall plan for ecological protection and high-quality development of the Yellow River basin, so as to make overall coordination and comprehensive treatment.