Abstract:[Objective] The carbon and water cycles in terrestrial ecosystems are the core of the material and energy cycles in terrestrial ecosystems, and also the link connecting the geosphere, the biosphere and the atmosphere. Forest vegetation is an important component of terrestrial ecosystems, an important variable characterized the terrestrial carbon-water cycle, and plays an important role in maintaining the dynamic balance of the biosphere and the atmosphere. Currently, there is a lack of systematic analysis and summary of the coupling relationship and mechanism of carbon-water cycle in terrestrial ecosystems. [Methods] This paper summarizes the research and its progress on forest vegetation carbon and water cycle processes and their interactions, as well as the definition, methods, progress and outlook of carbon-water coupling at different spatial scales (leaf to regional/global scales) from the perspectives of forest vegetation carbon and water processes and their interactions, and vegetation water use and coupling mechanisms, respectively. [Results] Emerging technologies and methods have realized high-frequency observations of hydrocarbon processes at different scales, and coupled indicator systems such as WUE have promoted the research and development of hydrocarbon coupling mechanisms.[Conclusion] In conclusion, we have systematically elucidated the multi-scale integration of vegetation carbon-water coupling relationship and carbon-water coupling mechanism, which provides a theoretical basis for the systematic understanding of forest carbon-water coupling mechanism and water resource management, and is of great significance as a scientific support for the future decision-making of vegetation operation and management.

Abstract:[Objective] In response to the controversy over the "source-sink" effects of hydraulic erosion on soil carbon cycle, the impact mechanism of hydraulic erosion on soil organic carbon mineralization and soil microbial diversity were reviewed and the directions and precautions of quantitative research in this field in the future were presented. [Methods] Based on the conception and theory of "source effects" and "sink effects" of hydraulic erosion on soil carbon cycle, the core issues of the current controversy over the "source-sink" effects of hydraulic erosion on soil carbon cycle were analyzed, and then the differences of soil microbial diversity changes among different types of soil microorganisms caused by hydraulic erosion and their mechanisms were discussed. [Results] The "source effects" of hydraulic erosion on soil carbon cycle were mainly caused by the organic carbon mineralization during erosion progress, while the "sink effects" were mainly caused by the migration of soil organic carbon to the low-lying areas for sequestration during deposition process. The respiration and decomposition of soil microorganisms resulted in the disappearance of carbon "sinks" in the soil carbon cycle. Hydraulic erosion process weakened the complexity of bacterial community structure, while the deposition process increased the complexity of bacterial community structure. However, both erosion and deposition processes weakened the α-diversity and the structure complexity of fungal community. Hydraulic erosion process indirectly impacted soil microorganisms diversity mainly through altering the soil organic carbon content, vegetation cover and soil pH. [Conclusion] Further research should strengthen the quantitative research on the influence mechanism of hydraulic erosion process on soil carbon cycle at different scales, the interaction mechanism between hydraulic erosion process and soil microbial diversity, as well as the influence mechanism of soil microorganisms on soil carbon cycle during hydraulic erosion progress.

Abstract:[Objective] This study aims to explore the effect of phosphorus on the fluid variability characteristics of sediment-laden flows. [Methods] A self-made double vertical tube rheometer was used to study the influence of phosphorus on fluid types, rheological parameters, and the critical threshold of fluid variation in sediment-laden flows with different concentrations. [Results] (1) Phosphorus concentration, sediment concentration, and physical and chemical properties of sediment were the main factors influencing the fluid variability in sediment-laden flows. At 25 ℃, the viscosity coefficient and Bingham yield stress increased by 0.48~1.47 mPa·s and 3.49~6.84 N/m², respectively, with an increase of 0.1 g/cm³ in calcium superphosphate concentration. (2) With the increase of phosphorus and sediment content, phosphorus-laden sediment-laden flows transitioned from Newtonian fluid to Bingham fluid. A computational model was developed and validated to calculate rheological parameters such as viscosity coefficient and Bingham yield stress. (3) The critical concentration threshold for the fluid variability of phosphorus-sediment-laden flows was given. When phosphorus concentration increased from 0 to 0.45 g/cm³, the critical concentration threshold for fluid variability in sediment-laden flows decreased by 49%, indicating that the presence of phosphorus accelerated the fluid variability of sediment-laden flows. Therefore, the increase of phosphorus promoted the process of erosion water flow from Newtonian fluid to Bingham fluid, which affected the energy dissipation process in the erosion flow. [Conclusion] The research findings provide a new scientific basis for in-depth understanding of the transport mechanism of erosive polluted water flows.

Abstract:[Objective] This study is aimed at investigating the effects of long-term fertilization and cultivation on the production of runoff and sediment on purple soil sloping cropland. [Methods] The experiment stipulated that each community should adopt the typical planting mode of winter wheat summer corn rotation on purple soil sloping cropland. Five treatments were set up on 15° purple soil slopes, which were no fertilizer application in downslope cultivation (CK), combined application of manure and fertilizer with downslope tillage (T1), single application of chemical fertilizer with downslope tillage (T2), single application of chemical fertilizer increment with downslope tillage (T3), and single application of chemical fertilizer with cross-slope monopoly cultivation (T4). There were three replications for each treatment. A total of 107 erosive rainfall events were monitored during 2008—2020, and the variation characteristics of runoff depth, sediment yield, and sediment concentration under each event rainfall and different fertilizer tillage treatments were analyzed. [Results] Among the fertilization and cultivation treatments, the maximum annual runoff depth per unit area was 100.37 mm, and the minimum was 4.56 mm. Except for the insignificant difference in runoff depth between T2 and T3 treatments (p>0.05), there was a significant difference in runoff depth between the other treatments (p<0.05), and the runoff depth of all treatments was significantly smaller than that of the CK treatment, and the mean values were in the order of CK>T3>T2>T1>T4. Except for the insignificant difference in sediment content between T1 and T2 treatments (p>0.05), there was a significant difference in sediment content between the other treatments (p<0.05), which were significantly smaller than the CK treatment, and the mean values were in the order of CK > T3 > T2 > T1 > T4. The sediment concentration showed no significant difference among T1, T2 and T3 (p>0.05), but they were significantly smaller than that of the CK treatment (p< 0.05) and significantly higher than that of the T4 treatment (p>0.05), and the mean values were in the order of CK > T3 > T1 > T2 > T4. The sediment content under each treatment was negatively correlated with rainfall amount with a power function (p<0.05). [Conclusion] The combined application of organic fertilizer and chemical fertilizer along the slope cultivation and cross-slope monopoly cultivation contributed greatly to the reduction of surface runoff and sediment production on purple soil sloping cropland.

Abstract:[Objective] Snowmelt erosion is one of the main forms of soil erosion in the black soil area of Northeast China, which plays an important role in land degradation in the area. The erosivity of snowmelt runoff is the key factor for calculating the erosion amount of snowmelt runoff, so it is of great significance to study the erosivity of snowmelt runoff. The erosivity of snowmelt runoff is mainly affected by snow depth, radiation intensity and warming rate, and its main driving forces include snowmelt rate and surface runoff. [Methods] The erosivity of daily average snowmelt runoff in the past 31 years was calculated, the temporal and spatial distribution characteristics of snowmelt runoff erosivity in the black soil area of Northeast China were analyzed, and the main influence factors of snowmelt runoff erosivity in each region were analyzed by using geographic detectors. [Results] The daily average snowmelt runoff erosivity in the three black soil subregions from 1990 to 2020 showed a trend of first increasing and then decreasing, and gradually stabilized in recent years, and the erosivity of daily average snowmelt runoff for many years was 0.01 (MJ·mm)/(hm²·h·a). Spatially, the erosivity of multi-year daily average snowmelt runoff was in the range of 0~0.21 (MJ·mm)/(hm²·h·a), showing a pattern of small in the middle and large in the surrounding areas. The influence factors of snowmelt runoff erosivity in spatial were as follows, the snow depth was large in the north and small in the south, the solar radiation intensity decreased from west to east, and the warming rate decreased from north to south. The influence factor of snowmelt runoff erosivity were analyzed by ground detector, and it was found that the warming rate had the strongest effect in the Mengdong black soil subregion, while the snow depth had the strongest effect in the Songnen black soil subregion and the Sanjiang black soil subregion. [Conclusion] Analyzing the spatiotemporal characteristics and influence factors of snowmelt runoff erosivity in the black soil region of Northeast China from 1990 to 2020 had certain theoretical and practical significance for deepening the study of snowmelt runoff erosivity characteristics and snowmelt erosion prevention in the study area.

Abstract:[Objective] This study intends to explore the main source of sediment and the evolution of erosion and sediment yield in Sanggan River Basin. [Methods] A typical warping dam in Gaoqiang Township, Yangyuan County was selected as the research object. The composite fingerprint identification technology was used to determine nine fingerprint factors, including soil particle size, SOC, TN, radionuclide (¹³⁷Cs) and low-frequency magnetic susceptibility, of sediment and its source areas. The evolution patterns of erosion and sediment production in different sedimentation stages of sediment source areas and dam controlled small watersheds were studied. [Results] (1) The average content of ¹³⁷Cs in sediment was relatively low, and it was not significantly different from that of gully wall soil, but it was extremely significantly lower than that of forest-grasslands and croplands soil (p<0.01), which indicated that the sediment was mainly from gully wall. (2) As the majority of ¹³⁷Cs content of gully wall was below the detection limit, ¹³⁷Cs was a good indicator for identifying gully wall as the main sediment source but it was difficult to be used for distinguishing multiple sediment sources in the small basin. Through Kruskal-Wallis H nonparametric test and multiple stepwise discriminant analysis screening, the optimal combination of fingerprint factors was TN+X_lfb+SOC, which effectively distinguished the average contribution rate of sediment source areas in small watersheds from 2006 to 2017. The contribution rate followed the order of gully wall (82.68%±8.20%) > croplands (15.36%±8.46%) > forest-grasslands (1.96%±0.33%). (3) In the evolution of erosion and sediment yield, gully wall was the main sediment contribution area for a long time, forest-grasslands had weak response to erosive rainfall, and the sediment contribution rate of croplands increased significantly when extreme rainstorm occurred. [Conclusion] Overall, the ¹³⁷Cs tracing technique was suitable for identifying the main sediment source in the small basin, and the composite fingerprint technique was better at identifying multiple sediment sources. The collapse of gully walls caused by gully erosion was the main cause of severe soil erosion in the Sanggan River Basin.

Abstract:[Objective] The soil erosion issue is very prominent in the karst region of southwest China and significantly affects the sustainable development of the regional economy. However, it is currently not very clear how the characteristic environmental factors of karst basins affect the direct driving force of soil erosion and runoff erosivity. [Methods] Taking the Yeji River Basin in the karst region of southwest China as an example and basing on the long-term and high-frequency field measurement data at the outlet hydrological station of the basin, the spatiotemporal change characteristics of runoff erosivity from 2005 to 2020 were evaluated and the influence of main karst environmental factors on runoff erosivity was analyzed by the Soil and Water Assessment Tool (SWAT) and the Partial Least Squares Model (PLSR). [Results] The average annual runoff erosivity was 2 326.47 m⁴/(km²·s), with strong spatial heterogeneity. In 2005, the high runoff erosivity was mainly distributed in the northern and central parts of the basin. During 2010—2020, the high runoff erosivity area gradually shifted to the central and southern parts of the basin. In terms of time, benefiting from the implementation of ecological restoration projects such as comprehensive control of soil and water loss in sloping farmland and comprehensive control of rocky desertification since the 11th Five-Year Plan, the runoff erosivity of the Yeji River Basin had been generally decreasing year by year. Lithology, exposed bedrock, and slope were the dominant control factors, which jointly explained 57.7% of the spatiotemporal variation of runoff erosivity in the Yeji River Basin. [Conclusion] These results can provide a theoretical reference for the comprehensive control of soil erosion in karst basins and help to formulate more precise and effective policies and measures to improve the ecological environment of the karst area and promote the sustainable development of the region.

Abstract:[Objective] Detecting the spatial and temporal variation characteristics of soil erosion in river basins and carry out sustainable river basin management. [Methods] This study quantitatively analyzes the temporal and spatial characteristics of soil erosion in Guishui River Basin by RUSLE model based on the rainfall, soil, digital elevation model (DEM) and land uses datasets of Guishui River Basin from 1995 to 2018, meanwhile, the soil stability in the basin was evaluated. [Results] (1) The areas of forestland and grassland showed a decreasing trend from 1995 to 2018, respectively. In 2018, the areas of forestland and grassland were 4.41×10⁴ and 0.84×10⁴ hm², respectively, which were 13.52% and 10.61% lower than those in 1995. The farmland area increased from 3.53×10⁴ hm² in 1995 to 4.07×10⁴ hm² in 2018. The area of building land has gradually increased, from 0.59×10⁴ hm² in 1995 to 1.90×10⁴ hm² in 2018. (2) The soil erosion modulus in Guishui River Basin fluctuated from 8.71 t/(hm²·a) in 1995 to 4.56 t/(hm²·a), and then increased to 11.07 t/(hm²·a) in 2018. (3) The intensity of soil erosion in Guishui River Basin is mainly in slight erosion. From 1995 to 2015, the intensity of soil erosion gradually decreased and remained stable, and the proportion of moderate and above erosion area decreased from 4.95% to 3.05%, and increase to 7.42% after 2018. (4) In Guishui River Basin, the soil stability decreased and the unstable soil area increased during the study period. [Conclusion] In the urbanization process of Guishui River Basin, the coverage of forest and grass decreased slightly; the intensity of soil erosion decreased totally, but increased slightly in the last stage; unstable soil land takes up a small proportion. The results of this study provide a basis for comprehensive management and land use planning of Guishui River Basin.

Abstract:[Objective] This study is aimed to understand the spatiotemporal changes in vegetation in the Qinghai Hehuang Valley and clarify the effects of climate change, land development and utilization and human activities on vegetation change. [Methods] The MODIS NDVI dataset from 2000 to 2020 was used to characterize vegetation changes. Based on Theil-Sen Median trend test, partial correlation analysis, geographical detectors and other methods, this paper explored the spatiotemporal changes of NDVI in Qinghai Hehuang Valley and its relationship with temperature, precipitation, slope, soil type, human activities and other influencing factors. [Results] (1) In the past 20 years, the vegetation NDVI in the Hehuang Valley region had shown a fluctuating growth trend, with a significant increase in the area of 2.21×10⁴ km² (p＜0.05), accounting for 53.39% of the total area of the Hehuang Valley. The area with a significant decrease in vegetation NDVI was 7.04×10² km² (p＜0.05), mainly distributed in the central part of the Huangshui Valley, accounting for 1.69% of the total area. (2) In terms of natural factors, the areas, in which NDVI was positively correlated with temperature and precipitation, accounting for 50.32% and 80.14% of the total area, respectively. The areas with significant vegetation increase were mainly distributed in areas with an altitude of 2 800~3 100 m, slope of 15°~20°, and a north facing slope. Within the range of elevation less than 3 200 m, vegetation NDVI changes showed an upward trend with the increasing of elevation, with a significant increase in the area accounting for 54.37% of the total area. In terms of human activity factors, the areas, in which NDVI was positively correlated with population density and nighttime lighting, accounting for 50.52% and 38.53% of the total area, respectively. Vegetation NDVI showed a significant upward trend in forests, shrubs, grasslands and construction land. (3) Based on the partial correlation analysis and the attribution analysis of vegetation NDVI changes by geographic detectors, it could be concluded that that there were obvious differences in vegetation changes among different soil types. Annual rainfall and human activities were the main influencing factors for vegetation NDVI changes in Hehuang Valley. The interaction between various influencing factors presented mutually reinforcing and non-linear enhancing relationships. [Conclusion] The spatiotemporal changes of vegetation NDVI in the Hehuang Valley were revealed, and the driving mechanisms of natural and human factors on vegetation NDVI changes were clarified, which could provide theoretical support for the future ecological protection, construction planning and the implementation of ecological engineering in Hehuang Valley of Qinghai Province.

Abstract:[Objective] Soil erosion is a prominent ecological problem in southwestern Hubei Province. A reasonable assessment of the vulnerability of soil erosion in this area and exploration of its driving mechanisms are prerequisites for effective soil and water conservation measures. [Methods] The effects of natural and socio-economic factors on soil erosion in southwest Hubei were analyzed from the perspective of the human-land coupling system. The evaluation index system of soil erosion vulnerability in southwest Hubei was constructed from three aspects: exposure, sensitivity, and adaptability. The comprehensive weighting method was used to determine the index weight. [Results] (1) From 2010 to 2020, the vulnerability of soil erosion in southwest Hubei generally showed a trend of decreasing first and then increasing. The vulnerability of soil erosion with strong and above intensity showed a fragmented distribution pattern, which was mainly concentrated in the central and southern parts of southwest Hubei and the western part of Yichang municipal district in the east. (2) The area with the highest sensitivity in the study area was concentrated at an altitude of 800 ~ 1 500 m, and the sensitivity was the largest at a slope of 25° ~ 35°, and showed a decreasing trend to both sides. When the slope was greater than 15°, the area with higher and higher sensitivity increased sharply; (3) Soil erosion vulnerability was higher than soil erosion intensity at higher and above soil erosion levels, and lower than soil erosion intensity at lower and below soil erosion levels. There was a synergistic trend between soil erosion vulnerability and soil erosion intensity. (4) The distribution pattern of soil erosion vulnerability was caused by a multi-factor synergy. The analysis of the geographical detector showed that slope, vegetation coverage, education quality, and urbanization rate have strong explanatory power for soil erosion vulnerability. [Conclusion] In the future, it is necessary to attach great importance to the protection of vegetation coverage in areas with a slope>15°, and to enhance the awareness of local residents about soil and water conservation by improving the quality of local education and strengthening the publicity of soil and water conservation.

Abstract:[Objective] In the landslide susceptibility assessment, the selection and optimization of the landslide prediction model are very important to the efficiency of the calculation process and the accuracy of the prediction results. Aiming at the problems that the existing single-objective genetic optimization algorithm (Genetic Algorithm, GA) is prone to premature maturity, poor local search ability, and slow global optimization speed, this paper develops a new optimization algorithm framework, which integrates the classic algorithm in the multi-objective genetic algorithm-Non-dominated sorting method with elite selection strategy (NSGA-II) combined with common machine learning algorithms, random forest (RF), and support vector machine (SVM) to predict landslide susceptibility. Different from single objective optimization, NSGA-II algorithm can perform feature selection and hyper-parameter optimization simultaneously, and make the prediction model achieve optimal accuracy, recall, precision and AUC (area under curve, AUC) at the same time. [Methods] Taking the Chongqing section of the Three Gorges reservoir area as the study area, the four optimized models (RF-GA, SVM-GA, RF-NSGA-II. and SVM-NSGA-II) were compared and analyzed in three aspects: model accuracy evaluation, landslide hazard susceptibility zoning map, and zoning statistics. [Results] NSGA-II was more effective than GA optimization, and in terms of model evaluation and landslide susceptibility zoning, the RF-NSGA-II model had higher predictive performance, with four evaluation values of 80.91%, 81.89%, 80.07% and 88.60% respectively, proving the effectiveness of the NSGA-II optimization algorithm; the area share of very low to very high hazard zones were in the order of 23.06%, 22.46%, 22.96%, 19.99%, and 11.53%, which verified the reliability of the RF-NSGA-II model. The susceptibility map predicted by the RF-NSGA-II model showed that the high and extremely high susceptibility areas were concentrated in the north and distributed in bands from east to west. [Conclusion] RF-NSGA-II algorithm based on multi-objective selection provides a new idea for the optimization of machine learning model for landslide risk assessment.

Abstract:[Objective] The Qinling-Daba Mountains region (QDM) is the important geographical transitional zone across the north and south of China. A comprehensive and systematic analysis of soil erosion in QDM is essential for the planning of soil and water conservation measures, and the sustainable agriculture development. [Methods] Based on the Revised Universal Soil Loss Equation (RUSLE), we calculate the soil erosion modulus in the QDM and analyze the spatiotemporal characteristic of the soil erosion in the study region from 2000 to 2020. [Results] (1) From 2000 to 2020, the areas of soil erosion in the QDM showed an upward trend. Spatially, the areas of higher soil erosion modulus were located in the northeast and southwest of the QDM, while the areas of lower soil erosion modulus were distributed in the central of the study region; (2) The areas with severe soil erosion are mainly concentrated in area with 500 ~ 1 500 m, and areas with 15 °~ 35°; (3) The land-use pattern with the highest soil erosion rates were forest, and the lowest soil erosion rate were found grass; (4) The areas with soil erosion were mainly located in Shaanxi, Sichuan, and Gansu. Severe erosion showed an upward trend in Gansu and Sichuan during 2000-2020. [Conclusion] Both erosion area and erosion intensity in the QDM showed decreasing trend, while the differences in the distribution pattern of erosion intensity were found in this study region.

Abstract:[Objective] On the basis of considering the differences of soil property, terrace form and rainfall type, we aimed to establish the estimation method and framework of water storage and retention efficiency of terrace. [Methods] By using soil reservoir calculation model and infiltration model, we explored the prediction methods of soil water distribution in saturation-excess runoff and infiltration-excess runoff. Moreover, based on the Richards equation, we analyzed the two-dimensional infiltration of soil profiles at different field and ridge boundaries. On this basis, we constructed the scenario of soil water movement under single runoff generation mode or two runoff generation modes under four types of rainfall patterns, including pre-peak rainfall, uniform rainfall, post-peak rainfall, and stepped rainfall patterns. [Results] We proposed the distributed estimation method of soil water storage efficiency of terrace field, and the maximum water storage capacity (W_M) of soil in a single terraced field was calculated. For different types of terraces, the anti-lateral seepage effect of stone walled bench terrace was the best, and the anti-lateral seepage effect of earth banked terrace was the worst, and the new soil ridge terrace with large pores, small density and short construction time lost more water than the soil ridge terrace with long construction time. The critical time (t) of full flow production under different rain patterns was obtained. [Conclusion] This estimation method could greatly reduce the dependence on field facilities and equipment, and reduce the input cost. With the help of field investigation and sampling, the efficiency of terraced water storage could be estimated based on model simulation. In addition, the method could be used to estimate the water storage efficiency of terrace on a regional scale according to the distributed calculation data of the water storage efficiency of a single terrace field, and provided a reference for the estimation of the water storage efficiency of different regional terraces.

Abstract:[Objective] The Yellow River Basin is an important ecological protection barrier in China, but its ecological environment is fragile. Studying the relationship between vegetation changes and water production services in the Yellow River Basin provides guarantees for its ecological construction and high-quality development. [Methods] Based on NDVI data and InVEST model, trend analysis and correlation analysis methods were used to combine vegetation change with water supply services. The temporal and spatial characteristics of NDVI and water production services in the Yellow River Basin from 2001 to 2020 were analyzed, and the trend changes and interrelationships between NDVI and water production services were studied. [Results] (1) The NDVI and water production depth of the Yellow River basin showed an increasing trend, with the growth rate of 0.05/10 a and 18.215 mm/10 a respectively. The NDVI was mainly showing a significant increase, while the water production depth was mainly showing an insignificant increase. In addition, the water production in the basin was also continuously increasing. (2) NDVI was closely related to water production depth, and there was a significant positive correlation between the two in terms of time, with a correlation coefficient of 0.75 (p <0.01). The spatial differentiation showed a positive correlation in the northeast and a negative correlation in the southwest. (3) The rate of increase in water production depth was highest under higher vegetation coverage, and NDVI was mainly positively correlated with water production depth under different vegetation coverage. However, as vegetation coverage increased, the proportion of negative correlation between NDVI and water production depth continued to increase. At present, the impact of NDVI on water production under various vegetation cover levels is positive, but as vegetation cover increases, its negative impact on water production depth will continue to increase. [Conclusion] In recent years, NDVI and water production services in the Yellow River Basin have shown a growth trend and are closely related. Currently, vegetation restoration still shows a positive effect on water production, but it should be noted that excessive vegetation restoration can have a negative impact on vegetation growth. Moderate vegetation restoration is beneficial for water production services in the Yellow River Basin.

Abstract:[Objective] Water and land resources are important factors of production for urban development. It is of great significance to explore the key factors in the utilization of water and soil resources in urban agglomerations in the middle reaches of the Yellow River to scientifically promote the rapid economic development of urban agglomerations in the middle reaches of the Yellow River. [Methods] Taking the three major urban agglomerations in the middle reaches of the Yellow River as an example, by using LMDI addition model, the decomposition models of factors affecting the change of water resources consumption and the change of urban construction land quantity were constructed respectively for the three major urban agglomerations in the middle reaches of the Yellow River from 2010 to 2019, and the effect values of different driving factors were calculated and compared. [Results] (1) Water use quota and industrial structure can inhibit the increase of water resource consumption, while economic scale and population scale will promote its increase. (2) The industrial scale, economic scale and population scale have a driving effect on the expansion of construction land, while the consumption intensity of urban construction land has a restraining effect on the expansion of construction land. (3) For the change of water resources utilization, there is a large gap in the optimization level of industrial structure among different cities in the middle reaches of the Yellow River; for the change of urban construction land, the comparison result of the total effect value of the three major urban agglomerations is Guanzhong Plain urban agglomeration > Central Plains urban agglomeration > Jinzhong urban agglomeration. [Conclusion] Discussing the factors affecting the utilization of water and land resources in urban agglomerations in the middle reaches of the Yellow River from the perspective of regional differences and time differences will help to enrich relevant research on the sustainable use of water and land resources, and provide theoretical guidance for the sustainable development of urban agglomerations in the middle reaches of the Yellow River.

Abstract:[Objective] In Shaanxi Province, the intensity of soil erosion in the Qinling-Daba Mountains is next only to that of the Loess Plateau. The study of response relationship between the intensity of summer day sunny and night rainfall (DSNR) and climate warming is of great importance for the control of soil erosion in China’s north-south transition zone. [Methods] Based on daily precipitation data in summer (June to August) of 72 meteorological stations, assisted by B-G segmentation, empirical orthogonal function (EOF) method and Lasso regression model, we analyzed the spatiotemporal variation and influencing factors of the intensity of DSNR at summertime in the north and south of Qinling mountains during the period 1970—2020. [Results] From 1970 to 2020, the intensity of DSNR in summer exhibited a significantly increasing trend, which was more obvious in Hanjiang River Valley [0.30 mm/(d·10 a)]. Spatially, the leading mode of the intensity of summer DSNR can be characterized by "consistent enhancement across the whole region, with a higher degree of anomalies in the valleys than in the mountains". It indicated that valley-plain areas below 1 000 m were sensitive to variations in the intensity of DSNR at summertime. In terms of influencing factors, the correlation between evolution in the intensity of DSNR at summertime and meteorological factors in the Hanjiang River Valley and southern slopes of Qinling Mountains was higher than that in Guanzhong Plain. In addition, cumulative duration of sunshine was the leading climatic factor driving the changes of summer DSNR intensity in the southern slopes of Qinling Mountains, while the variations of summer DSNR intensity in the Hanjiang River Valley was jointly influenced by cumulative duration of sunshine and average wind speed. [Conclusion] The year 2003 was a mutation year after which the intensity of DSNR at summertime began to be greater in the north and south of Qinling mountains. It informs us that, in the north and south of Qinling mountains, we should put the focus of soil and water conservation on the precipitation type with high temperature in the day and heavy precipitation at night.

Abstract:[Objective] Exploring the impact of hydropower development on local climate is an important guarantee for preventing and mitigating the possible negative effects of hydropower development and realizing sustainable energy development and environmental protection. [Methods] Four typical hydropower stations, Longkaikou and Guanyinyan in the middle reaches of the Jinsha River and Xiluodu and Xiangjiaba in the lower reaches of the river, were selected. By applying the climatic propensity rate, the M-K trend test, and the wavelet analysis, this study quantitatively analyzed the monthly, seasonal and yearly changes of temperature and precipitation before and after the impoundment of water in the middle and lower reaches of the river, as well as the sudden changes in the development of hydropower and the cyclical characteristics. [Results] (1) After water storage, the hydropower station had an inhibitory effect on the highest temperature and an uplifting effect on the lowest temperature in the valley. In summer and autumn, the downstream hydropower station played a cooling role, and the average monthly temperature decreased significantly in February, June, July, September, October and November, while the midstream hydropower station did not have the temperature regulation effect, with only a slight decrease in average air temperature in July. (2) After water storage, precipitation in each season increased significantly, with an increase of 0.71~27.95 mm in April, August, and September. (3) Air temperature and precipitation were related to hydropower development, and the air temperature and precipitation of the mid-and downstream hydropower stations underwent abrupt changes at different times during the development and after the water storage. (4) Air temperature and precipitation showed similar characteristics in wavelet change period, and after water storage, local precipitation showed more significant periodicity and had a certain degree of stability. [Conclusion] At different time scales, hydropower development affected local temperature and precipitation varied across river reaches, and was constrained by multiple factors such as geographic location, the surrounding environment and water storage duration.

Abstract:[Objective] Identifying the sensitivity of disasters is an important prerequisite for disaster prevention and reduction, and sensitivity assessment of complex disaster systems is an important component of risk assessment of composite disaster systems. [Methods] Firstly, the sensitivity assessment index system of the composite disaster system was constructed according to the characteristics of the rainstorm landslide disaster chain, and then the susceptibility of the rainstorm-landslide disaster chain in Guangdong-Hong Kong-Macao Greater Bay Area was evaluated by using Convolutional Neural Network (CNN) and Optimal Parameters-based Geographical Detectors-Analytic Hierarchy Process (OPGD-AHP). Through the sensitivity analysis of rainstorm and landslide, the sensitivity classification maps of rainstorm and landslide in the Greater Bay Area were obtained respectively. And the threshold value and conversion probability of landslide induced by rainstorm were obtained through statistical analysis, so as to analyze the sensitivity of rainstorm landslide disaster chain and finally the sensitivity classification map of the rainstorm-landslide disaster chain in the Greater Bay Area was obtained. [Results] (1) The highly sensitive areas of the rainstorm landslide disaster chain in Guangdong, Hong Kong and Macao were mainly distributed in the northwest of Guangning County and Huaiji County, and in the east of Huiyang District and Huidong County. (2) The sub high sensitivity and medium sensitivity areas were mainly distributed in areas such as Fengkai, Deqing, Conghua, Longmen, Boluo, etc. (3) Low sensitivity areas and sub low sensitivity areas were mainly distributed in central areas such as South China Sea, Liwan, Chancheng, Shunde, Nansha, Panyu, Sanshui, Baiyun, etc. [Conclusion] The research results could provide scientific basis and technical support for disaster prevention and reduction, as well as enhancing the resistance and resilience of the disaster chain in Guangdong-Hong Kong-Macao Greater Bay Area.

Abstract:[Objective] This study is aimed to explore the physiological and biochemical manifestations of Bougainvillea spectabilis Willd. to low temperature and the intrinsic adaptation mechanism to cold stress in the context of climate change. [Methods] Taking Bougainvillea Paederia Foetida, Bougainvillea Flaming Sumba and Bougainvillea Duranta with strong, medium, and weak cold tolerance as test materials, through indoor pot experiments, we conducted low temperature treatments for 7, 14 and 21 days and studied the responses of the photosynthetic and antioxidant systems of different cold tolerant Bougainvillea to cold stress during these different periods. [Results] (1) During the low-temperature treatment period, the initial fluorescence (F₀) of all varieties increased, with the most significant change in B. Paederia Foetida, which increased by 60.2% compared to day 0. Maximum fluorescence (F_m), PSII effective photochemical electron production (F_v/F_m), and photosynthetic relative electron transfer rate (ETR) rapidly decreased and reached their lowest levels at day 21. As the intensification of low temperature stress, the photochemical quenching coefficient (qP) of the three Bougainvillea types decreased, while the non-photochemical quenching coefficient (qN) of B. Flaming Sumba and B. Paederia Foetida increased significantly. (2) After exposure to low temperature stress, the activities of SOD, POD and CAT enzymes in each variety decreased significantly and intensified with the extension of stress time, indicating that low temperature seriously inhibited the antioxidant enzyme activity of Bougainvillea. Among them, the SOD, POD and CAT enzyme activities of B. Paederia Foetida were higher than those of the other two varieties, indicating that B. Paederia Foetida had strong cold resistance. (3) In the AsA-GSH cycle system, the content of AsA and DHA of each Bougainvillea leaf significantly increased under low temperature. Compared to day 0, the GR activity of the three Bougainvillea types at day 21 increased by 180.91%, 175.97% and 112.37%, respectively. Additionally, the AsA/DHA ratio, APX activity and DHAR activity of B. Paederia Foetida significantly increased at day 21. [Conclusion] Low temperature inhibited plant growth through affecting the PSII photochemical reaction center. However, Bougainvillea could activate their photosynthetic system protection mechanism to reduce photoinhibition. Furthermore, it could accumulate osmoregulation substances, activate the antioxidant system, and exert stress regulatory effects to eliminate rapidly proliferating ROS in its own body and alleviate low-temperature damage.

Abstract:[Objective] Intensive research on the spatial and temporal response characteristics of meteorological drought to vegetation at different time scales in the Yellow River Basin provides valuable information for ecological conservation, water resource management, and climate change adaptation, and can mitigate the environmental and economic problems caused by drought. [Methods] Based on the standardized precipitation evapotranspiration index (SPEI) and normalized vegetation index (NDVI) for the Yellow River Basin during the period of 1982—2020, image-by-image metric linear regression models, Sen’s trend analysis and Mann-Kendall test were used to study the spatial and temporal distribution characteristics of meteorological droughts at different time scales in the Yellow River Basin, as well as their impacts on vegetation. [Results] (1) From 1982 to 2020, the Yellow River Basin showed an insignificant increasing trend in aridity, with regions exhibiting negative trends in SPEI mainly concentrated in the western region from Longyangxia to Lanzhou, the southern part of the Yellow River Basin, and the surrounding areas of the Hetao Plain. (2) The spatial distribution pattern of average vegetation coverage in the Yellow River Basin demonstrated a decreasing trend from south to north and from southeast to northwest. The proportion of regions with a significant increase in vegetation coverage (61.94%) was greater than that of those with a significant decrease (5.43%). (3) In most areas of the Yellow River Basin, drought conditions were positively correlated with vegetation status. Regions exhibiting significant positive correlations were mainly concentrated in the northwest and northernmost areas of the Yellow River Basin, indicating that vegetation in these areas was severely affected by drought. (4) Grassland and cultivated land showed the strongest response to drought at a six-month time scale, while forests and unused land were more vulnerable to long-term drought compared to other land types. All four landform types were susceptible to medium- to long-term water shortages, with vegetation in hilly areas being the most affected by drought. [Conclusion] The results of the study provide an effective scientific basis for disaster prevention and mitigation as well as ecological environment construction in the Yellow River Basin, and provide important information for ecological protection, water resource management and climate change adaptation in the Yellow River Basin, which will help to formulate more precise policies and measures to mitigate the potential impacts of drought on the environment and the economy, and to promote sustainable development.

Abstract:[Objective] The carbon compensation mechanism is an important way to promote the achievement of carbon peaking and carbon neutrality goals and social environment equity. [Methods] This study established the carbon compensation model to calculate the amount of spatial transfer carbon compensation based on the calculation of the carbon budget from 2010 to 2020. [Results] (1) During the study period, the average annual incremental rate of total carbon emissions was 2.51%, with the remaining cities except Foshan, Dongguan and Qingyuan increasing to varying degrees, presenting a spatial pattern of "core-periphery" centered around Guangzhou. From 2010 to 2020, the total carbon absorption showed a slow downward trend, and the spatial pattern tended to be stable with a general characteristic of high in the northern and low in the southern. (2) The carbon compensation payment area became larger during the study period, the proportion of area increased from 55.22% to 60.49%. The payment regions were mainly distributed in Huizhou, which had higher net carbon emissions, and Yunfu and Yangjiang, which had lower net carbon emissions but lower carbon emission efficiency. The compensated areas were mainly divided into two types, one type exhibited low net carbon emissions, e.g., Heyuan and Shanwei, and the other type was of high carbon emissions but high carbon emission efficiency, such as Shenzhen, Guangzhou and Dongguan. (3) Huizhou ranked the first of the compensation amounts to be paid, while Shenzhen received the largest amount of carbon compensation. The proportion of cross regional carbon compensation amounts to the regional GDP of each city varied from 0.017% to 0.095%, indicating that cross regional carbon compensation was feasible. [Conclusion] In order to achieve the low-carbon collaborative development of Guangdong province, it is needed to establish carbon compensation system guided by the government in the future and implement the low-carbon-oriented regional differentiation low-carbon optimization strategy. The above has important practical significance for regional coordination and low-carbon development.

Abstract:[Objective] Regional carbon storage is closely related to land use. Under the goal of "carbon peaking and carbon neutrality", researches about land use change calculations in significant regions play an important role on coordinating and optimizing regional land use patterns, improving the future carbon sequestration potential of regional ecosystems. [Methods] Taking Western Sichuan Plateau as the study area this paper predicts land use changes under different scenarios from 2020 to 2030, and estimates regional carbon storage changes by using revised land use carbon density data and land use data in 2000, 2010 and 2020. [Results] (1)From 2000 to 2020, grassland gradually decreased from 65.20% to 63.65%, forest continuously expanded from 31.73% to 32.92%, unused land firstly decreased and then increased and the net increase rate is 0.57%, water area and farmland firstly increased and then decreased and their net decrease rate is 0.11% and 0.11%, wetlands continued to increase by 0.07%; The carbon reserves of the study area in 2000, 2010 and 2020 were 24.26×10⁸,24.29×10⁸,24.27×10⁸ t, showing a trend of first increasing and then decreasing.(2) Carbon storage reduced 3.19×10⁵ t under natural development scenario. Under farmland protection scenario, ecological protection scenario, and farmland ecological joint protection scenario, their carbon sequestration will be respectively 4.29×10⁶, 9.72×10⁶, 9.60×10⁶ t. [Conclusion] Reversing the increasing trend of unused land, continuing to steadily implement ecological protection policies with maintaining the cultivated land area, improving the carbon sequestration potential, and helping the Western Sichuan Plateau become an important "carbon sink" area should become the key points of land spatial planning and control on the Western Sichuan Plateau.

Abstract:[Objective] To optimizing the pattern of territorial space development and coordinating the pattern of production-living-ecological space is the key task and fundamental way to achieve sustainable development in the future. [Methods] Based on the land use in Yunnan Province and combined with the natural and social development factors, the MOP-PLUS coupling model was used to simulate the changes of production-living-ecological space and its effects under three scenarios of economic priority, ecological priority and collaborative development in 2030. [Results] (1) Under the three scenarios, the economic benefit increased by 40.29%, 32.10% and 34.79%, the ecological benefit decreased by 0.89%, 0 (unchanged) and 0.06%, the average habitat quality decreased by 0.78%, 0.38% and 0.43%, and the average spatial conflict intensity increased by 2.79%, decreased by 1.21% and decreased by 2.32%. (2) Living space increased and ecological space decreased in the three scenarios. Production space only increased slightly in the economic priority scenario. In all cases, living space encroached on production space, and then production space plagued ecological space. The expansion of living space showed a trend of encroaching from the center to the periphery. (3) Habitat quality decreased to some extent under different development scenarios, and spatial conflicts could be balanced by optimizing spatial layout. Compared with other scenarios, the growth of economic benefits in the collaborative development scenario was moderate, the variation range of habitat quality was relatively balanced, and the intensity of spatial conflicts decreased the most, which was in line with the multiple goals of ecological protection, economic development and social progress. [Conclusion] The simulation-effect-optimization feedback regulation mechanism formed in this paper can be combined with different scales and objectives to carry out land use change simulation and effect analysis, and provide a basis for decision-making of territorial space allocation.

Abstract:[Objective] From the perspective of socioeconomic development transition, this study aims to explores the spatiotemporal characteristics of land use change in the middle reaches of the Yangtze River (MRYR). [Methods] The method of change range and change speed of land use change, as well as geographical information map were employed. [Results] (1) The socioeconomic development stage of the MRYR have undergone two transition processes during 2000—2018. The first is from the primary production stage II to the middle industrialization stage, with slow growth of urbanization and serious outflow of population. The second is from the middle industrialization stage to the late industrialization stage, with steady growth of urbanization and continuous return of population. (2) In terms of overall characteristics, the cultivated land area continues to decrease, the water area and construction land area continue to increase, the woodland, grassland and wetland area obviously decrease, and the unused land area remains relatively stable. (3) In terms of process characteristics, in 2000—2010, cultivated land and forest land were transformed into each other, cultivated land into construction land and water area, and water area into wetland were the main change types. In 2010—2018, cultivated land and construction land were transformed into each other, forest land into construction land and cultivated land, and wetland into water area were the main change types. (4) In terms of trajectory characteristics, the early change type is the main type, followed by the late change type and repeated change type, and the proportion of continuous change type is small. [Conclusion] The stage characteristics of land use change in the MRYR are obvious, which is manifested in the change of land use quantitative and spatial structure caused by the scale and direction of transformation between different land use types in different transition periods of socioeconomic development.

Abstract:[Objective] The Silk Road Economic Belt facilitated rapid economic development in cities along its route, resulting in significant changes in land use. Investigating the carbon stock variations caused by land use in this region was crucial for optimizing land use patterns and achieving the carbon peaking and carbon neutrality goals. [Methods] The PLUS-InVEST model was employed to assess and predict the carbon stock situation in five provinces and cities along China’s Maritime Silk Road between 1980 and 2030. The model simulated the spatiotemporal characteristics of carbon stock changes under multiple scenarios of land use, aiming to explore the impact of land use on carbon storage. [Results] The research findings indicate that over a span of 50 years, there has been a significant reduction in arable land and a substantial increase in construction land in the region. Forest land has managed to maintain a basic dynamic equilibrium during this period. However, there has been a considerable loss of carbon storage with an accelerating rate, primarily in the southern Guangdong-Hong Kong-Macao Greater Bay Area, northern Shanghai, Hangzhou, and along the coastal areas. [Conclusion] Through current status and multi-scenario analysis, it is projected that future carbon storage reduction will be primarily influenced by the loss of arable land and the rapid expansion of construction land. In scenarios focused on ecological preservation, there is some increase in carbon storage, while scenarios that maintain the current level of construction land result in a substantial decrease in carbon storage. It is evident that the region is currently experiencing accelerated economic development, with the exacerbation of carbon storage loss attributed to the loss of arable land and the acceleration of urbanization. The key factor in mitigating carbon storage loss lies in maintaining a dynamic balance in the total forest land area. Considering the current economic development status and regional position, it is advisable to rigorously safeguard the quantity of arable and forest land while intensively utilizing existing construction land. Furthermore, enhancing the quality of ecological land, such as grasslands, is recommended to preserve the regional ecological carbon storage level. This research provides valuable insights for achieving a harmonious balance between economic and ecological development in the context of the Maritime Silk Road initiative.

Abstract:[Objective] This study intends to comprehensively explore the land ecological security situation of the Shandong Peninsula and Jiziwan of the Yellow River, provide a realistic basis for realizing the ecological protection and high-quality development of the Yellow River Basin and promoting the strategy of "jointly grasping the great protection and jointly promoting the great governance". [Methods] The entropy method, kernel density estimation, Markov chain and obstacle factor model, and other methods were applied. [Results] (1) In terms of level change, the growth rate of land ecological security in the two regions was "inverted U" type. The level of land ecological security in Shandong Peninsula was obviously higher than that Jiziwan of the Yellow River, but the growth rate of Jiziwan of the Yellow River was faster. (2) In terms of time, the land ecological security of the two regions had the characteristics of "single core" evolution. The regional differences in Shandong Peninsula were expanding, while the regional differences in Jiziwan were narrowing. In space, the two regions showed a spatial distribution trend of "high in the middle east and low in the west". (3) On the evolution characteristics, the evolution of land ecological security level in the two regions had the effects of "path dependence" and "self-locking". (4) The ecological security of land in Shandong Peninsula was affected by the per capita cultivated land area and the average application amount of chemical fertilizers and pesticides. The ecological security of land in Jiziwan of the Yellow River was affected by landscape fragmentation and forest coverage. [Conclusion] In the future, Shandong Peninsula and Jiziwan of the Yellow River should not only classify and implement policies according to regional advantages, but also proceed from the overall situation of the basin to jointly improve the land ecological security level of the Yellow River Basin.

Abstract:[Objective] Evaluating regional land use efficiency and its coupling relationship from three aspects of society, economy, and ecological environment is beneficial for achieving rational allocation of land resources and optimizing land use structure. [Method] In this paper, taking 21 cities and prefectures in Sichuan Province as the research objects, a comprehensive evaluation system for land use benefit in Sichuan Province from 2010 to 2020 was constructed using the entropy weight TOPSIS method and coupling coordination degree model. Based on GIS technology, the coupling coordination relationship and spatiotemporal evolution characteristics of the social, economic, and ecological environmental benefits of land use were analyzed. [Result] (1) the overall comprehensive land use benefit of various cities and prefectures in Sichuan Province was on the rise, with a spatial pattern of "high in the northwest and low in the southeast". The overall economic benefits of land use and ecological environmental benefits were showing an upward trend, manifested as a spatial pattern of "high in the west and low in the east" and "high in the central and western regions and low in the west", respectively. The overall social benefits of land use were showing a downward trend, with a spatial pattern of "high in the middle and low in the two wings". The three major benefits all had significant clustering characteristics in space. (2) There were four levels of land use coupling coordination in various cities and prefectures in Sichuan Province, with an overall coordination level that was not high, mainly being barely coordinated, followed by a near imbalance, and the spatial pattern being "high in the middle and low on the two wings". Cities with the same coupling level had higher aggregation, and the land use benefit coupling coordination level needs further improvement in spatial distribution. (3) The factors that affect the size of land use benefit in Sichuan Province were in the order of social > economic > socio-economic > social ecology > ecological environment benefit system. The coupling and coordination relationship of land use benefits was mainly influenced by a single factor of social and economic benefits, followed by social and economic composite factors, and then social and ecological composite factors. [Conclusion] The overall comprehensive benefits of land use in various cities and prefectures in Sichuan Province were on the rise, with significant regional differences. The overall level of coupling coordination was at a lower level, and cities with the same coupling level had a higher degree of agglomeration. In future development, it is necessary to regulate the disorderly expansion of urbanization, pay attention to the construction of urban basic public services and other facilities, and increase the investment in urban environmental construction, promote the coordinated development of land economic benefits, social benefits, and ecological environmental benefits in Sichuan Province. The research conclusion aims to provide a reference for improving the comprehensive benefits of land use in Sichuan Province.

Abstract:[Objective] Ecological land plays an important role in maintaining ecological balance and supporting economic development. It is of great practical significance to study the spatio-temporal evolution characteristics and driving mechanism of ecological land use in central Yunnan urban agglomeration to optimize the ecological security pattern, promote the construction of ecological civilization in Yunnan, and build a strong ecological security barrier in southwest China. [Methods] Based on the identification of ecological land use in the central Yunnan urban agglomeration from 1990 to 2020 by Google Earth Engine (GEE) cloud platform, the spatial and temporal change trajectory and driving mechanism of ecological land use in the central Yunnan urban agglomeration were explored by using change trajectory analysis, hot spot analysis and geographic detector. [Results] (1) The change of ecological land in the central Yunnan urban agglomeration mainly occurred in the transition zone between non-ecological land and forest land, and the change between ecological land (forest land and grassland) mainly occurred in the mountainous area in the north and south of the study area. (2) The changes of ecological land use are mainly less of high frequency and low frequency, and the frequency changes show obvious aggregation effect in the hot and dry valley of Yuanjiang River, the hot and dry valley of Jinsha River and the karst zone of East and southeast Yunnan; (3) The influence of social and economic factors on ecological land use is significantly higher than that of natural factors. Driven by natural environment, cultivated land expansion and ecological restoration policies, the interaction of multiple factors has more explanatory power on ecological land use change. [Conclusion] The ecological land in the urban agglomeration of central Yunnan Province is broken, the change of natural environment and the increasing human activities can easily lead to the change of ecological land, and it is urgent to formulate reasonable ecological protection measures by region to build a strong ecological security barrier in southwest China.

Abstract:[Objective] The study is aimed at revealing the response of runoff to land use change in the Kuye River Basin and predicting future runoff change. [Methods] Taking the Kuye River Basin as the study area, based on the SWAT and PLUS models, the changes of runoff under different land use scenarios were quantitatively analyzed by using the land use data of 2000, 2005, 2010, 2015, 2020 and the data of 2025 and 2030 that were predicted from the natural development scenario. [Results] (1) The R² and NS of the SWAT model during the periodic and validation periods were greater than 0.7. The overall accuracy of PLUS model was 0.877 4, and the Kappa coefficient was 0.802 1. The two models had good applicability in the Kuye River Basin. (2) From 2000 to 2020, forest land and construction land increased by 102.92 and 600.90 km², respectively, while cultivated land, grassland, water area, and unused land decreased by 277.15, 366.25, 40.44 and 19.98 km², respectively. (3) The average annual runoff depth in the Kuye River Basin presented a spatial distribution pattern of "lower in the upper reaches, higher in the lower reaches, lower in the west, and higher in the east". (4) Changing land use data while ensuring that other input data remains unchanged, the results of scenario analysis showed that the decrease of forest land and grassland area would promote runoff, and the increase of construction land area would also promote runoff. (5) Under the natural development scenario, there was no significant change in the spatial distribution pattern of land use in the Kuye River Basin in 2025 and 2030, and the land use was still dominated by cultivated land and grassland, with the average annual runoff increasing by 3.21% and 5.00%, respectively, compared with 2020. [Conclusion] There was a close relationship between land use and runoff change. From the perspective of scenario analysis, forest land and grassland inhibited runoff, while construction land promoted runoff. Under the future natural development scenario, runoff increased with land use change. The research could provide scientific basis for the optimization of land use structure and rational planning of water and soil resources in the Kuye River Basin.

Abstract:[Objective] This study is aimed to scientifically construct the ecological network of urban agglomerations in the middle reaches of the Yangtze River, and to provide scientific basis and theoretical reference for cross-regional ecological protection and collaborative governance. [Methods] Multi-temporal ecological network was conducted based on the framework of "source identification-resistance surface construction-corridor extraction", and network evaluation was done based on network attributes and human activities. [Results] (1) Ecological sources were mainly concentrated in the mountainous of northwestern Hubei Province, junction of Jiangxi and Hunan, and the basin of Poyang Lake basin, with the area reducing from 2.67×10⁷ km² in 2000 to 2.29×10⁷ km² in 2020. The number of ecological corridors decreased from 69 to 42, and the total length decreased from 1.53×10⁴ km to 1.16×10⁴ km. The resistance of study area increased gradually, the center of gravity of network had shifted from Hubei Province to Hunan Province, transforming from a strip distribution of "three horizontals and two verticals" to a concentrated group distribution. The overall degree of aggregation and network connectivity of the ecological network were weakening, and showing a trend of structural contraction and functional weakening overall. (2) In network optimization, 102 ecological "breaking points" were identified, and 17 stepping stones were set based on the distance between the source and destination. A "core protection belt" and an "ecological control belt" were set up within 5 and 15 km of the network, with length of 1 505 km. [Conclusion] In synergistic governance, at the provincial level, Hubei and Jiangxi provinces should improve the cross-provincial ecological compensation mechanism for river basins, while Hunan and Jiangxi provinces should strengthen the judicial guarantee in the implementation of the synergistic mechanism. At the city level, differentiated management and control would be implemented for key management areas, and potential ecological corridors would be planned to promote synergistic governance at the city level. The integration of the optimized ecological network was improved from 0.22 to 0.30, effectively improving ecological connectivity between regions.

Abstract:[Objective] The Three Gorges Reservoir’s impoundment has speed up habitat fragmentation and patching in the water level fluctuation zone, and extreme habitat stress has seriously damaged the structure and function of vegetation. Clarifying the habitat status of the water level fluctuation zone of the Three Gorges Reservoir, proposing an adaptive vegetation restoration strategy, and reconstructing the comprehensive ecological function of damaged river corridor are of utmost importance for building regional ecological security pattern and ensuring water resources security of the Yangtze River Basin. [Methods] In response to the prominent issues of vegetation degradation and ecological function damage, we systematically analyzed multiple habitat conditions and their influence on riparian vegetation growth. Focusing on the basic requirements for ecological restoration of damaged river corridor along reservoir banks, a vegetation restoration pattern for construction of suitable microhabitats and optimization of vegetation functional pattern was explored. [Results] The habitat conditions of the water level fluctuation zone were jointly regulated by unique water level rhythm formed by reservoir, operation, climate condition during the exposed, soil erosion and sedimentation and soil environment, which presented a distinctive spatial heterogeneity pattern. Among these, inundation duration, emergence time, and inundation intensity by seasonal water fluctuation were the primary factors affecting plant reproduction and development, while soil erosion, sedimentation burial and soil substrates affected vegetation growth. [Conclusion] Accordingly, water level, site conditions and morphological-functional trait characteristics of various vegetation should be comprehensively considered when planning vegetation restoration in the water level fluctuation zone. Meanwhile, the high-quality stress-resistant species selection, site preparation measures for soil condition improvement, and the zonal optimization of vegetation patterns were beneficial for rebuilding the comprehensive ecological function of the water level fluctuation zone. This provided theoretical support and scientific basis for the ecological management of the water level fluctuation zone in the Three Gorges Reservoir.

Abstract:[Objective] The Ten Tributaries Basin, an important part of Yellow River Jizi Bay, exhibits a sensitive and fragile ecological environment. Investigating the alterations in land use and identifying the driving forces behind these changes are essential for fostering high-quality development within the Yellow River Basin, which holds significant ecological implications. [Methods] Employing remote sensing images from the years 1986, 2000, 2010 and 2020, This study analyzed the land use changes in the Ten Tributaries Basin using the spatial analysis via ArcMap 10.8 and Principal Component Analysis (PCA). [Results] The results showed a gradual expansion in forestland, construction land, and cultivated land over the periods studied, while unused land, grassland, and water bodies demonstrated a reduction trend. By 2020, forestland had emerged as the predominant land category, covering an area of 6 308.43 km², accounting for 59.99% of the total area. The highest comprehensive dynamic attitude was observed between 2010 and 2020 at 1.59%, indicating the most substantial changes in land use during this period. The plain area, with its relatively flat terrain, witnessed expansions in cultivated land and construction land. In contrast, due to ecological management policies and projects, the sandstorm area saw a transformation of unused land into forestland and grassland, especially evident in the eastern sandstorm area. A small proportion transformed into photovoltaic power generation areas in the central sandstorm area. In the hilly area, the primary shift was from unused land to forestland, although a minimal conversion from forestland to industrial and mining area occurred in the southeastern hilly area due to the region’s advanced industrial and mining activities. Water bodies within the Tributaries Basin decreased by 75.81 km², whereas the cultivated land along the coast increased significantly, except in the northern plain area. Land use change was mainly driven by socio-economic factors, agricultural productivity, topographical conditions, and policy initiatives. [Conclusion] Over the past 35 years, the Ten Tributaries Basin has experienced considerable land use changes, with a notable positive shift in overall ecological conditions. The results of this study provide a scientific reference for policy-making entities in formulating ecological protection policies within the Yellow River Basin.

Abstract:[Objective] To explore the nutrient characteristics and fertility status of wetland soil in the lower reaches of Lhasa River. [Methods] A total of 69 soil samples were collected from the four representative regions of Ganqu Wetland, Baga Snow Wetland, Lalu Wetland and Chabalang wetland. The values of pH, total nitrogen, total phosphorus, total potassium, total salt, electrical conductivity, redox potential, cation exchange capacity and organic matter of the samples were determined. The improved Nemerow composite index method was used to evaluate the wetland soil fertility comprehensively. [Results] (1) The pH range of the soil in the study area was 5.77~7.78, with an average value of 6.62, which was neutral. The correlation between organic matter and total nitrogen was strong, and the distribution characteristics were similar. The contents of organic matter and total nitrogen were 61.82 and 3.13 g/kg, respectively, and both were very abundant, belonging to the first level. The contents of total phosphorus and total potassium were 0.75 g/kg and 18.05 g/kg, respectively, which were moderate and belonged to the tertiary level. The total salt content is 0.92 g/kg, and the electrical conductivity is 2.97 mS/m. On the whole,the soil in the study area had strong fertilizer retention ability. (2) The soil comprehensive fertility coefficient (P) of wetland was in the order of Chabalang Wetland (2.01) > Bagaoxue Wetland (1.95) > Lalu Wetland (1.93) > Ganqu Wetland (1.86), all belonging to the fertility level. The index affecting the soil comprehensive fertility of wetland was TP, because the formation conditions of natural wetlands were similar. There was no significant difference in soil comprehensive fertility coefficient. [Conclusion] The present situation of wetland soil nutrients in the lower Lhasa River was clarified,which provides scientific basis for realizing the sustainable utilization of wetland resources in the the study area.

Abstract:[Objective] This study is aimed at comprehensively evaluating the soil quality of different vegetation restoration types in the mountainous areas of Beijing, and further identifying the key factors affecting soil quality, so as to provide data support for vegetation restoration and reconstruction in the region. [Methods] The study utilized various vegetation types, including Platycladus orientalis pure forest, Pinus tabulaeformis pure forest, P. orientalis-P. tabulaeformis mixed forest, P. orientalis coniferous and broadleaved mixed forest, P. tabulaeformis coniferous and broadleaved mixed forest, deciduous broad-leaved mixed forest, and non-forest land (CK), with similar stand conditions, as research objects. Fourteen soil physical and chemical indicators were measured to establish the total data set (TDS) for evaluating soil quality. Principal component analysis (PCA) and Pearson correlation analysis were employed to determine the minimum data set (MDS) for soil quality evaluation. Two scoring methods, linear (L) and non-linear (NL), were used to calculate the soil quality index (SQI) and a general linear model (GLM) was employed to identify key factors influencing soil quality. [Results] The bulk density and sand content decreased, while the content of soil nutrients such as organic matter, total nitrogen, total potassium, available nitrogen, and available potassium increased after the vegetation restoration compared with the non-forest land. The screened MDS indicators for soil quality evaluation in the study area were total nitrogen (TN), sand content, total potassium (TK), pH, and available water capacity (AWC). Under the four methods (SQI-LT, SQI-NLT, SQI-LM, and SQI-NLM), the SQI values of different vegetation restoration types were ranked as deciduous broadleaf mixed forest > P. orientalis coniferous and broadleaved mixed forest > P. tabulaeformis pure forest > P. tabulaeformis coniferous and broadleaved mixed forest > P. orientalis-P. tabulaeformis mixed forest > P. orientalis pure forest > non-forest land, and the soil quality significantly improved after vegetation restoration. The soil quality evaluation method of SQI-NLM exhibited better applicability in the mountainous areas of Beijing. Compared with non-forested land, the SQI-NLM of other vegetation restoration types improved by 64%, 48%, 45%, 36%, 33% and 27%, respectively. The GLM model accounted for 85.24% of the total variation in the soil quality index, with vegetation type explaining the largest proportion of the soil quality index (45.09%). [Conclusion] The selection of suitable vegetation restoration types is crucial for improving regional soil quality. In future vegetation restoration efforts, priority should be given to broad-leaved species in tree species selection. Additionally, the choice of silvicultural configuration should depend on the tree species, such as introducing native broad-leaved species into Platycladus orientalis pure forest to form a Platycladus orientalis coniferous and broadleaved mixed forest, or selecting Pinus tabulaeformis pure forest as the optimal silvicultural model.

Abstract:[Objective] In order to know the changes of nutrient content and distribution of soil aggregates under Larix gmelinii plantation of different forest ages after vegetation restoration in severely burned areas of Greater Khingan Mountains.[Methods] Takes the Larix gmelinii plantation (11,21 and 32 years) planted in 1989, 2000 and 2010 on the severely burned areas formed by the severe forest fire in Greater Khingan Mountains in 1987 as the research object. By measuring the contents of organic carbon, total nitrogen, total phosphorus, alkali-hydrolyzed nitrogen, available phosphorus and available potassium in soil aggregates, the nutrient distribution characteristics of soil aggregates were studied. [Results] (1) The contents of organic carbon, total nitrogen, total phosphorus, alkali-hydrolyzed nitrogen and available potassium in soil aggregates of different particle sizes increased gradually with the decrease of particle size, and the content of < 0.5 mm particle size was the largest. (2) As the age of forest increased, the content of organic carbon, total nitrogen, total phosphorus, alkali hydrolyzed nitrogen and available phosphorus in soil aggregates gradually increased. The nutrient content of soil aggregates in 32 years Larix gmelinii plantation was significantly higher than that in 11 years Larix gmelinii plantation. The contents of organic carbon, total nitrogen, total phosphorus, alkali-hydrolyzed nitrogen and available phosphorus in soil aggregates were significantly increased by 77.35%~130.24%, 77.61%~143.36%, 105.84%~147.98%, 94.58%~155.96% and 206.98% ~ 537.09%, respectively, compared with 11 years Larix gmelinii plantation (p < 0.05). The organic carbon content of soil aggregates at different particle sizes in 21 years was higher than that in 11 years Larix gmelinii plantation, but there was no significant difference. (3) There was a strong correlation between organic carbon and total nitrogen and alkali-hydrolyzed nitrogen in soil aggregates (p < 0.01). Soil organic carbon and alkali-hydrolyzed nitrogen content had the strongest correlation with < 0.25 mm fraction content. Total nitrogen, total phosphorus, available phosphorus and available potassium had the strongest correlation with > 0.25 mm fraction content (p < 0.01). [Conclusion] The nutrient of soil aggregates in Larix gmelinii plantation showed surface aggregation. The nutrient content of soil aggregates in Larix gmelinii plantations planted on severely burned areas in Greater Khingan Mountains increased with the increase of forest age. The Larix gmelinii plantation planted for 32 years significantly increased the nutrient content of soil aggregates. The results provide a scientific basis for the restoration of artificial vegetation in the severely burned area of Greater Khingan Mountains.

Abstract:[Objective] To construct ecological benefit evaluation methods adapted to the characteristics of local plantation resources and ecological services, and clarify the impacts of different types of plantation construction on the ecological environment in the eastern, central and western parts of the region. It provides a theoretical basis for accurately quantifying and scientifically evaluating the ecological service function of the plantation in different regions, optimizing the stand structure of the plantation, formulating the ecological compensation intensity standard of the plantation, accurately measuring and evaluating the carbon sink of the plantation, and transforming the "green appearance level" into "ecological value". [Methods] In the construction of the loess plateau ecological forest, ecological economic forest, economic forest of weihe effective area calculation model based on the investigation and determination of typical area and forest survey to collect data and measurement parameters, such as the method of combining calculation analysis of the different types, different regions of the eastern, central and western plantation water conservation, carbon sequestration release oxygen, conservation of soil and purify the atmosphere of ecological benefits. [Results] (1) The ecological benefits of different types of plantation in Weibei Loess Plateau were ecological forest > economic forest > ecological economic forest; The value of water conservation is the highest, the value of soil conservation and carbon fixation and oxygen release is the second, and the value of air purification is the lowest.(2) The ecological benefits per unit area of plantation were economic forest > ecological forest > ecological economic forest. (3) The ecological benefits of plantation were in the middle > East > west. [Conclusion] Ecological forest and economic forest play an important role in the ecological benefits, and increasing their proportion can significantly improve the ecological benefits of plantations. In order to improve the ecological benefits of plantations in Weibei-loess plateau, ecological forest should strengthen the transformation of sparse forest, the cultivation of virgin forest and the sealing of shrubland. At the same time, moderate development of economic forest can effectively improve the ecological benefits of artificial forest in the west and even the whole Weibei Loess Plateau.

Abstract:[Objective] For the joint application of double-row high vertical nylon mesh sand barriers and grass checkerboard sand barriers, wind tunnel experimental studies were conducted to optimize the configuration of nylon mesh sand barriers porosity in the joint sand barriers and investigate the sand control benefits of the joint sand barriers under each porosity. [Methods] Based on the wind tunnel simulation experimental data, we carried out the characterization of the changes in the wind velocity flow field, aerodynamic roughness, friction wind velocity, sand transport rate with height, and sand blocking rate of the joint sand barriers with different porosities (40%, 45%, and 55%) at different wind speeds. [Results] (1) The area of wind shadow zone of the joint sand barrier was the largest at 40% porosity of nylon mesh sand barrier under the same wind speed. (2) As the porosity of the nylon mesh sand barrier increases, the aerodynamic roughness and friction wind speed decreased, and the values of aerodynamic roughness and friction wind speed of the joint sand barrier at 40% porosity were the largest at the same wind speed and the same location. (3) The sand transport rate on the surface increased with the increase of wind speed. Inside and on the leeward side of the joint sand barriers, the sand transport rate decreased exponentially with the increase of height, and the sand transport was mainly concentrated at the height of 0~12 cm. (4) Wind speed and sand barrier rate showed a negative correlation; sand barrier rate and porosity also showed a negative correlation, the porosity of 40% of the joint sand barriers had a better sand barrier rate; double rows of high vertical nylon mesh sand barriers and grass checkerboard sand fixation measures combined with the sand barrier rate superposition also existed. [Conclusion] Therefore, the combination of double-row vertical nylon mesh with 40% porosity and grass checkerboards can realize better configuration and sand control benefits.

Abstract:[Objective] Saline water irrigation is one of the important ways to alleviate the shortage of agricultural water and ensure food production. However, soluble salt in irrigation water leads to soil salt accumulation, which affects the growth of crops. Seeking a suitable salt concentration in irrigation water is a favorable guarantee for the safe utilization of saline water resources. [Methods] In this study, a rain-shielding pot experiment was conducted to plant winter wheat. The deionized water was used as a control (CK), and chloride salts were added to form saline water with different salt concentrations. The electrical conductivity of irrigation water (EC_w) was 0.26 (CK), 3.00 (S1), 5.26 (S2), 7.07 (S3), and 9.24 (S4) dS/m respectively. The soil water and salt distribution, growth, photosynthetic physiology, and yield formation of winter wheat were studied. [Results] Soil water content and electrical conductivity increased with the increase of saline water salt concentration under saline water irrigation. When the conductivity of irrigation water was 9.24 dS/m, the soil moisture content was 5.43% (0—10 cm), 4.21% (10—20 cm), and 4.98% (20—40 cm) higher than CK, respectively. The electrical conductivity of soil extract (ECe) in 0-40 cm soil layer was 0.66, 4.89, 7.88, 9.34, and 10.16 dS/m under CK and S1-S4 treatments after winter wheat harvest, respectively. Compared with CK, there was no significant difference in the growth, photosynthetic physiological indexes, and yield of winter wheat when the conductivity of irrigation water was 3.00 and 5.26 dS/m, but it was significantly reduced when the conductivity of irrigation water was 7.07 and 9.24 dS/m. The net photosynthetic rate, maximum plant height, maximum leaf area, shoot dry matter mass at maturity stage, root dry matter mass and yield of winter wheat under 9.24 dS/m were decreased by 71.00%, 2.81%, 15.33%, 15.55%, 47.25%, and 27.53% compared with CK, respectively. The threshold of saline water conductivity for irrigation of winter wheat was calculated as 5.82 dS/m using the fitting sum of FAO piecewise function, if the value exceeded, the relative yield of winter wheat decreased by 8.80% with each increase of 1 dS/m. [Conclusion] In summary, the higher the salt concentration of irrigation water, the greater the impact on soil water and salt distribution and winter wheat growth, 5.82 dS/m is the threshold of saline water conductivity of winter wheat irrigation. Considering the growth, photosynthetic physiological indexes of winter wheat and soil physical and chemical properties, it is suggested that EC_w should not exceed 5.82 dS/m when saline water is used to irrigate winter wheat. This study can provide theoretical support for the safe utilization of saline water.

Abstract:[Objective] Stressed by harsh environmental factors such as scarce precipitation and large evaporation, the desert Gobi is characterized as spare vegetation and severe soil and water losses. Therefore, exploring suitable soil improvement methods to improve soil water retention and water holding capacity is very important for the development of Gobi ecological agriculture. [Methods] The hydraulic-infiltration characteristics of the 3 groups of coconut coir-type ecological conservation substrates with better physicochemical properties (aeolian soil: coconut coir: organic fertilizer: artificial peat = 3.5:3:3:1 or 3:4:3:1 or 2:5:3:1, i.e., T1, T2, T3) were tested compared to the control substrate with no coconut coir (aeolian soil: organic fertilizer: artificial peat = 7:3:1, T0). The relationship between matrix water and suction was determined by the centrifuge method, and then the hydraulic characteristics were explored. Then, the infiltration characteristics of the substrates were analyzed by the indoor infiltration test of the soil column with constant water head; and, based on the measured indicators, the proportion optimization was carried out by the coordinate comprehensive evaluation method. [Results] Compared with the T0 group, the field water retention capacity of the T1, T2 and T3 groups increased by 10.22%, 12.13% and 14.99%, and the total effective water content increased by 8.10%, 8.81% and 12.83%, respectively. In the stage of P_f=1.8~3.8 (logarithmic matrix suction), the average specific water capacity of each group showed a law of T3 > T2 > T1 > T0, and according to the gray correlation analysis (RGA) method, the infiltration capacity was ranked as T3 > T2 > T0 > T1. [Conclusion] The results showed that a suitable proportion of coconut coir mixing changes the effective water content and pore distribution ratio, which can significantly improve the water retention capacity of the substrate. From the perspective of physicochemical properties, hydraulic and infiltration characteristics, the T3 ratio is optimal.

Abstract:[Objective] The Loess Plateau is a great geographical unit of China, which has important strategic significance for national food security and ecological security. Through long-term slope management, comprehensive watershed management, afforestation and other measures, the ecological environment of the Loess Plateau has been significantly improved, but it still faces challenges in such aspects as insufficient rationality of vegetation restoration in local areas, uncoordinated overall planning of the whole basin, and balanced economic development and ecological protection. Under the guidance of the national dual-carbon goal, the future direction and goal of the Loess Plateau ecosystem and agricultural sustainable development should be to support the realization of carbon neutrality, establish an environmentally suitable vegetation community, promote the development of the ecosystem as a whole, and realize the green transformation of the development mode. [Methods] Based on the bibliometrics tool CiteSpace, this paper visually analyzes the relevant literatures on the principle and application of soil regulation in the Loess Plateau published from 1992 to 2023, focusing on the core research strength, research hotspot and research trend in this research field. [Results] (1) From the perspective of the evolution of the number of published papers, the overall trend is rising, and the growth rate is explosive after 2001; (2) From the perspective of publishing institutions, Northwest A&F University has the highest number of publishing institutions in this field, with 2 157; (3) From the perspective of the cooperative relationship between authors, Academician SHAO Mingan and Professor LIU Guobin are the core leaders in this field, and the number of published papers is 141 and 117 respectively. The cooperative network formed by them has been very mature; (4) From the perspective of research hotspots and development trends in this field, the main research hotspots focus on soil moisture, yield, dryland, soil erosion, soil nutrients and vegetation restoration, etc. The future micro theme trend will focus on yield, slope position and nitrogen application amount, while the future macro trend will explore a new model of the coupling and coordinated development of eco-economic-social system. [Conclusion] Based on the results of visual analysis, three perspectives on the principles and application of soil regulation in the Loess Plateau were proposed, including cooperative research, research hotspots and future key development directions.