Abstract:[Objective] The relationship between laterite disintegration characteristics and the occurrence of slumping erosion was investigated in order to provide a theoretical basis for slope management. [Methods] The basic parameters of slumping slopes such as slope gradient and angle of repose were measured; the characteristics of laterite agglomerates and the disintegration process under alternating wet and dry conditions were experimentally determined; and the conditions of the slope, stability of laterite water-stable agglomerates, and changes of the disintegration characteristics of the slumping erosion area were analyzed. [Results] ① Slope gradient and angle of repose were two factors that influenced the occurrence of slumping erosion. Sloughing was unusual in loess plateau areas with slope gradients of 40° or less and was considerably weakened by gradients greater than 80°. The natural angle of repose between red soil and slumping slopes varied from 25° to 36°. ② Most of the laterite agglomerates easily disintegrated when exposed to water because they were non-hydrostable and had weak stability, resulting in sloughing and erosion. The average mass diameter (MWD) and geometric mean diameter (GMD) of the laterite agglomerates were 2.16 mm and 1.37 mm for dry sieve and 0.51 mm and 0.25 mm for wet sieve, respectively. The percentage of agglomerate destruction (PAD) was 57.66%, with a fractal size D of 2.96. aggregate stability index (ASI) is a metric that represents the overall stability of agglomeration in the transfer matrix method, and the red clay ASI in this study was 1.75. ③ Dry-wet alternation reduced the rate of slumping erosion by reducing laterite disintegration. The highest disintegration index was 81.79%, and the average disintegration rate was 51.03 g/min. The disintegration degree of the laterite was lowered under the dry-wet alternation condition compared to under the natural state. The maximum disintegration index of the laterite varied between different dry-wet alternation circumstances but the difference was not statistically significant. ④ Laterite disintegration rates were favorably linked with the angle of repose, slope gradient, and ASI (p＜0.01) of the slumping erosion. [Conclusion] Laterite disintegration properties are directly related to slumping erosion, and dry-wet alternation reduces the rate of slumping erosion by reducing laterite disintegration.

Abstract:[Objective] The effect of simulated acid rain on the shear strength characteristics of red clay was investigated and the influence strength mechanism and microstructure of red clay after acid rain corrosion was analyzed in order to provide theoretical and engineering guidance for the construction of infrastructure in acid rain area, especially the protection of roadbed slope and safe operation of infrastructure. [Methods] The red clay of a roadbed slope in Kunming City, Yunnan Province was used as the research object. The study adopted the static soaking test and used pure water and acid liquor with different concentrations to soak and erode the red clay for 7, 14, and 28 days. Thereafter, the shear strength of the red clay was measured using the direct shear tests, and the microstructures of the eroded soil samples were analyzed via electron microscope scanning and energy spectrum analysis to analyze the influence mechanism of strength. [Results] ① The effect of acid liquor on the stress-strain characteristics of red clay is significant, especially under high concentration acid. The stress-strain curve was unstable and increased like a step, with strain hardening characteristics. ② With the increase in soaking time and acid concentration, the shear strength of red clay and its index of cohesion and internal friction angle gradually decreased, and the acid concentration had a more significant effect on the strength and its index. ③ Acid liquor decreased the sequioxide and the interparticle adhesion and bonding force and simultaneously increased the internal pores, loosened the structure, and increased the soil moisture content, thereby resulting in a decrease in shear strength and cohesion; however, the overall decrease in particle size caused by acid was the main reason for the decrease in the internal friction angle. [Conclusion] Acid rain has a significant effect on the strength of red clay from roadbed slope, and the intensity of acid rain has a more significant effect on the strength than the duration of rainfall. Attention should be paid to the prediction and prevention of roadbed slope stability and the safe operation of highway infrastructure.

Abstract:[Objective] The infiltration process and characteristics of the slump body in the alpine grassland blanket layer in the source region of the Yellow River were analyzed to provide data and theoretical basis for the slump body deformation and damage prevention and soil and water conservation. [Methods] This study used the alpine grass felt layer slump body in the source area of the Yellow River as the research object. The relationship curve between infiltration rate and time and the permeability coefficient of the slope grass felt layer slump body in the Eling Lake area of the Yellow River source were obtained through the double loop permeability test, and the suitable permeability model was determined. [Results] The infiltration rate of the grass felt layer slump body in the study area generally decreased sharply and then gradually flattened with the increase of infiltration time. The average permeability coefficients of the three test points were (5.81±2.18)×10^-3, (4.53±0.82)×10^-3, and (4.42±0.51)×10^-3 cm/s, respectively, and there was no significant difference between each other. Compared to the Kostiakov model and the general empirical model, the Horton model had a higher applicability in simulating the water infiltration process of the grass felt layer slump body in the study area. [Conclusion] The Horton model is more suitable for simulating the water infiltration process of the grass felt layer slump body.

Abstract:[Objective] The water sources of alfalfa and seabuckthorn under different vegetation allocation patterns in drought and rainy seasons were studied to provide a theoretical basis for vegetation restoration in mining areas. [Methods] The platform of the dumping site of Manlailiang coal mine in Ordos City, Inner Monglia Autonomous Region was taken as the research area. The stable isotope technique was used to collect plant xylem samples, soil samples, and precipitation samples under three vegetation configuration modes in the study area, and the hydrogen and oxygen stable isotope compositions were analyzed. [Results] ① With the advent of the rainy season, the soil moisture content of all plots showed an increasing trend. The pure seabuckthorn land increased from 6.56% in the dry season to 9.88%, the pure alfalfa land increased from 7.94% to 9.15%, and the mixed land increased from 9.4% to 15.45%. ② Alfalfa and seabuckthorn mainly used 80—100 cm soil water as their water source under different vegetation configuration modes in the dry season. In the rainy season, with the supplement of rainfall to soil water, the soil moisture content increased, and the water absorption depth of various types of vegetation moved up, mainly concentrated at 20—60 cm. [Conclusion] The water sources of alfalfa and seabuckthorn were very different in the dry and rainy seasons under different vegetation configuration modes. In the dry season it was mainly concentrated in deep soil, and the water absorption depth moved up and the water absorption range increased in the rainy season. To avoid resource competition, seabuckthorn will choose deep soil water as its main water source under the mixed condition in the rainy season.

Abstract:[Objective] The dynamic pattern of soil enzyme activities and its relationship with soil chemical properties in a subtropical Pinus armandii forest was investigated to provide reference for the study of nitrogen deposition in subtropical regions. [Methods] Four nitrogen gradient treatments for the control (CK) and low (LN), medium (MN), and high nitrogen (HN) at 0, 10, 20 and 25 g/(m²·a), respectively, were set up in the subtropical Pinus armandii forest of Central Yunnan to analyse the response of soil enzymes to nitrogen deposition and its correlation with soil chemical properties. [Results] ① Nitrogen deposition promoted the activities of invertase (16.94%—34.00%) and acid phosphatase (23.42%—40.09%) and inhibited the activities of urease (8.70%—27.18%) and catalase (9.26%—23.36%), with temporal variation (p<0.05). Invertase and urease activities were highest at 25th and 27th month after nitrogen deposition (August and October, 2021), whereas acid phosphatase and catalase activities were highest at 33th month after nitrogen deposition (June, 2022). ② Soil pH value, organic carbon, and total phosphorus content decreased with increasing nitrogen deposition; in contrary, soil nitrate and ammonia nitrogen content increased in MN and decreased in HN. ③ Soil chemical properties and enzyme activities were characterized by a vertical soil layer distribution of 0—5 cm >5—10 cm >10—20 cm. The synergism between different soil enzyme activities under nitrogen deposition was high (p<0.05), among the environmental factors affecting soil enzyme activities, soil total nitrogen was the most sensitive factor affecting invertase activity; soil organic carbon, total phosphorus, and ammoniacal nitrogen were the most sensitive factors affecting urease and catalase activities. [Conclusion] With continuously increase in nitrogen deposition, the synergism among soil enzymes was enhanced, the environmental factors affecting forest soil were changed, the soil enzyme activity was promoted or inhibited, and then the soil nutrient cycling was changed too.

Abstract:[Objective] The change of wind erosion characteristics of physical crust under freeze-thaw conditions was studied to provide theoretical reference for the study of freeze-thaw wind erosion. [Methods] The study examined sandy loess of the Liudaogou sub-watershed in Shenmu City, Shaanxi Province, situated within the wind and water erosion crisscross region of the northern Loess Plateau. The synergistic approaches of indoor freeze-thaw simulation and wind tunnel testing were used to assess the impact of freeze-thaw cycles on wind erosion intensity, sand transport rate, and kinetic parameters such as friction wind speed and aerodynamic roughness across varying soil physical crust coverage levels (0%, 20%, 40%, 60%, 80% and 100%). [Results] ① Wind erosion intensity was found to increase significantly with increasing wind speed (p＜0.05) and decrease with increasing incrust coverage (p＜0.05), and the maximum reduction in erosion rate was up to 96.07%. Compared to that under pre-freeze-thaw condition, there was a significant rise in the wind erosion intensity of physical crusts under post-freeze-thaw condition, and the increase ranged from 0.02 to 1.27 times. ② Physical crust coverage significantly reduced the near-surface sand transport, which decreased with increasing crust coverage and increased with increasing wind speeds. After freeze-thaw cycles, the near-surface sand transport rates increased by 0.7 to 4.3 times, and the transport height increased by 2 to 10 cm. ③ Changes in friction wind speed and aerodynamic roughness in response to variations in crust coverage were not statistically significant. The friction wind speed before freeze-thaw was between 0.84 and 1.35 m/s, and post-freeze-thaw varied from 0.80 to 1.51 m/s. Although the friction wind speed was slightly reduced after freeze-thaw, the aerodynamic roughness exhibited minimal variation. [Conclusion] In the northern part of the Loess Plateau, the protective effects of physical crusts against wind erosion reduced and soil wind erosion was intensified by freeze-thaw processes. With increased crust coverage, there was a more noticeable increase in wind erosion intensity and near-surface sand transport following freeze-thaw cycles. The influence of crust coverage and freeze-thaw processes on aerodynamic roughness is negligible.

Abstract:[Objective] The tensile and shear resistance characteristics of the riparian alpine meadow rooted soil and the influencing factors along the riverbanks of the Yellow River source area were analyzed to provide data support for research on riverbank protection and the mechanical mechanisms of riverbank failure in the source area. [Methods] Taking the meandering river Lanmucuoqu in Henan County, Qinghai Province, as the study area and the rooted soil of alpine meadows with varying degrees of degradation along riverbanks as the research object. The effects of water content, root content, root system composition, and the number of freeze-thaw cycles on the tensile and shear strength of root-bearing soil were analyzed. The relationship between the tensile and shear strengths of the root-bearing soil was also explored. [Results] The tensile and shear strengths of the rooted soil gradually decreased as the water content increased from 30% to 55%, and the shear strength was approximately five times than that of the tensile strength. The addition of plant roots effectively improved the tensile and shear strength of the soil. As the root content increased from 0% to 0.25%, the tensile and shear strengths increased by 45% and 107%, reaching maximum values of 4.38 and 19.98 kPa, respectively, when the proportion of gramineous plants was 100%. After multiple freeze-thaw cycles, the fitting curve of the root-bearing soil showed a bimodal pattern, with the original network structure of the soil first being destroyed and then reaching a new equilibrium as the number of freeze-thaw cycles increased. A linear correlation was observed between the tensile and shear strengths of root-bearing soil. [Conclusion] The degradation of alpine meadows in the Yellow River source area has led to significant changes in root quantity and root system morphology, resulting in a gradual decrease in the tensile and shear strengths of the rooted soil. Therefore, it is necessary to minimize overgrazing and human interference to protect the native alpine meadow vegetation along riverbanks and maintain the stability of riverbanks in the source area.

Abstract:[Objective] The effects of rainfall levels, planting patterns and their interactions on slope sediment yield and loss in metamorphic rock areas were studied to provide references for soil and water conservation, land management strategies and vegetation allocation in Dabie Mountains area. [Methods] Experimental investigations on soil erosion in runoff plots with three distinct planting patterns (monoculture of Camellia oleifera, monoculture of Camellia sinensis, and mixed planting of C. oleifera and C. sinensis at intervals) were carried out in Panxin Town, Luoshan County, Dabie Mountains. Instruments such as soil erosion monitors and tipping bucket rain gauges were used to monitor real-time runoff and rainfall in the year 2023. Variance analysis and correlation analysis were conducted to investigate the impact of rainfall variables and planting configurations on runoff and sediment yield. [Results] The monoculture of C. sinensis plot exhibited the highest runoff, and the mixed planting plot demonstrated significantly lower runoff compared to the monoculture plots, but no significant variance in sediment yield among the plots (p＞0.05) without considering rainfall levels. Under light and moderate rainfall, there was no significant distinction in runoff among the plots; however, the sediment yield in the mixed planting plot was notably lower than that in the other plots, particularly under moderate rainfall conditions. During periods of intense and prolonged rainfall, the runoff in the mixed planting plot exhibited a statistically significant decrease compared to the monoculture plots (p＜0.05). However, there was no significant variance in sediment yield among the plots. Both runoff and sediment yield showed a significant correlation with total rainfall and hourly rainfall, but runoff was additionally influenced by the maximum 60-minute rainfall intensity. [Conclusion] Compared to the monoculture practices of C. oleifera or C. sinensis, the mixed planting pattern demonstrated a notable decrease in runoff on slopes within the metamorphic rock regions of the Dabie Mountains. Furthermore, sediment yield under light to moderate rainfall conditions was effectively mitigated. Attention should be paid to soil and water conservation, land management strategy formulation, and vegetation allocation in Dabie Mountains area in the future.

Abstract:[Objective] The soil and water conservation benefits of vegetation measures were analyzed under different land use types for the small catchment from the mountainous areas in the Central Yunnan Plateau to provide scientific basis and theoretical guidance for rational planting and improvement of land use status in the area. [Methods] The Jianshan River small catchment from Yuxi City of Yunnan Province was selected as the study area, and the rainfall data were collected from 2012 to 2022. The runoff and sediment yield characteristics and their influencing factors under different land use types (secondary forest, artificial forest, shrub land, cultivated land, economic fruit forest) were analyzed based on the runoff and sediment data from the runoff plots. [Results] ① The order of runoff from different land uses was in the order of cultivated land ＞economic fruit forest ＞shrub land ＞secondary forest ＞artificial forest, and the order for sediment yield was cultivated land ＞artificial forest ＞economic fruit forest secondary forest＞shrub land. The erosion resistance of cultivated land was worse than that of other land use types under the same rainfall conditions. ② A significant positive correlation was determined between sediment yield and runoff (p＜0.01). The sediment delivery lagged behind the runoff generation. Only when the runoff was ≥0.02 mm for the secondary forest, ≥0.46 mm for shrubland, ≥0.4 mm for artificial forest, ≥0.62 mm for economic fruit forest, and ≥0.09 mm for cultivated land could they carry sediment. ③ Runoff and sediment yield were significantly correlated with vegetation coverage, rainfall, soil capillary water-holding capacity, soil capillary porosity, and total soil porosity (p＜0.05). [Conclusion] This study has an important practical significance for scientifically setting up the layout of vegetation types, reasonably allocating the land planting pattern, and laying out the farmland consolidation.

Abstract:[Objective] The pedo-transfer functions was established through the simple and easily measurable soil properties, and the soil saturated hydraulic conductivity was obtained indirectly, in order to provide data support for soil water transport and simulation of typical agricultural small watershed of the Three Gorges reservoir area. [Methods] Using the Shipanqiu watershed of the Three Gorges reservoir area as the research object, the soil saturated hydraulic conductivity (K_s) and other basic physical and chemical properties of typical land use types (cultivated land, garden land, and grassland) were measured. In addition to correlation and principal component analysis, multiple linear regression (MLR), BP neural network (BP-ANN), and support vector machine (SVM) methods were used to construct pedo-transfer functions for the saturated hydraulic conductivity of the surface soil in the study area. Furthermore, four common pedo-transfer functions were selected to verify their applicability in this study area. [Results] The average soil K_s values were in the order of grassland>garden>cultivated land, with significant differences among different land use types. The saturated hydraulic conductivity of the soil was significantly correlated with bulk density, organic matter content, saturated water content, and soil texture. Compared with the K_s pedo-transfer functions established through multiple linear regression, BP neural network, and support vector machine, the previously used soil transfer functions model have poor prediction performance for soil saturated hydraulic conductivity in this study area. The forecast accuracy of the transfer function created using the three methods was in the order of SVM>BP-ANN>MLR, and the forecast accuracy created using principal component P₁ and P₂ as input variables was better than others. [Conclusion] The K_s values under different land use types have strong spatial variability. The pedo-transfer functions built through BP-ANN and SVM can meet the prediction requirements of K_s in this study area, and the prediction accuracy of SVM is better than that of BP-ANN.

Abstract:[Objective] This study assessed of soil and water loss and evaluation of the benefits of measures caused by rainstorms. Soil erosion caused by rainstorms was analyzed, and the benefits of terrace measures were evaluated to provide an effective supplement for the dynamic monitoring of soil and water loss. [Methods] The Qingcheng County and Qiugou small watershed of the rainstorm (2022·7·15) center in Gansu Province were used as the research areas based on daily rainfall data and the results of the national dynamic monitoring of soil and water loss projects. An improved Chinese soil loss equation(CSLE) model was used to calculate the soil erosion modulus based on the rainfall erosivity of rainstorms. The relationship between rainfall erosivity of the rainstorm and annual rainfall erosivity under the condition of multiannual average rainfall was analyzed. The spatial distribution of the soil erosion intensity grades of different land-use types under rainstorm conditions was further analyzed, and the influence of terraces on regional soil erosion was discussed. [Results] The rainfall erosivity generated by this rainstorm in Qingcheng County reached 1.85 times the annual rainfall erosivity under the condition of multiyear average rainfall, and the rainfall erosivity of the rainstorm center reached 4.88 times the annual rainfall erosivity under the condition of multiyear average rainfall. The area of soil erosion above the strong level caused by rainstorms was 3.46 times, and the rainstorm center was 6.93 times that of the soil erosion above the strong level in 2021. Strong soil erosion caused by heavy rainstorms was primarily distributed in dry lands, grasslands, and shrubs. The current terrace area of Qingcheng County is 325 km². The amount of soil erosion in the county decreased by 72.87% compared to the situation without terrace measures. [Conclusion] Strengthening soil and water conservation work, such as returning farmland to forest and grassland, comprehensively improving sloped farmland, and constructing dry terraces, is an effective means of preventing and controlling soil and water loss disasters under heavy rainstorm conditions.

Abstract:[Objective] The patterns and mechanisms of farmland conversion to non-agricultural were explored in the hilly regions of Northeast Guangdong Province (NGP) to provide theoretical guidance for preventing Farmland Conversion to Non-agricultural. [Methods] Using NGP as an example, information on farmland conversion was extracted land-use images for the years 1990, 2000, 2010, and 2020. Spatial autocorrelation analysis and optimal parameter geographic detector methods were employed to investigate the spatiotemporal distribution characteristics and factors influencing farmland conversion. [Results] ① From 1990 to 2020, farmland conversion to non-agricultural in NGP exhibited a trend of “steady development followed by a sharp decline”, with a cumulative non-agriculturalized area spanning 2.29×10⁵ hm² at a rate of 25.31%. Forestland and constructed land were identified as the primary types of non-agricultural land. ② Vertically, croplands above 1 000 m in elevation and with a slope of 25°—35° were more prone to non-agriculturalization; horizontally, croplands within 50 m of construction land and 1 000—1 500 m from rivers were more likely to undergo non-agriculturalization. ③ Cropland non-agriculturalization in NGP exhibited significant positive clustering, with Global Molan’s I gradually decreasing from 0.371 to 0.255. The changes in “high-high” and “low-low” clustering dominated the evolution of the spatial autocorrelation pattern of cropland non-agriculturalization rates. ④ Agricultural population and cropland fragmentation consistently had strong explanatory power for the spatial distribution of cropland non-agriculturalization. In contrast, the explanatory power of socioeconomic factors for non-agriculturalization has weakened over the past decade. The interaction of multiple factors, especially agricultural and socioeconomic factors, can further enhance the explanatory power of cropland non-agriculturalization. [Conclusion] From 1990 to 2020, the area and spatial clustering of farmland conversion to non-agricultural in NGP decreased. However, the impact of the agricultural population and farmland fragmentation on farmland conversion to non-agricultural has intensified. It is suggested to reasonably control the speed of urban expansion, consolidate fragmented farmland, introduce small-scale agricultural machinery to improve farming conditions, and encourage farmers to cultivate by promoting rural e-commerce to address the issue of farmland conversion to non-agricultural.

Abstract:[Objective] The distribution characteristics of water pollution risk in inland river basins were analyzed. A regional assessment was conducted to provide theoretical support and reference for the study of water pollution risks and incidents in inland river basins. [Methods] Geographic information system (GIS) spatial analysis was used to refine and visualize the degree and distribution of water pollution risk based on environmental statistical data, digital elevation model(DEM) data, water quality monitoring section data, and basic geographic data of the Heihe River basin in 2021, and a 1 km×1 km grid as the basic unit. The environmental risk field was used to assess the water pollution risk in the Heihe River basin and to analyze the distribution characteristics of water pollution risk zoning. [Results] Only a few areas in the Heihe River basin were at high-risk levels. Severly polluted water systems were mainly concentrated in the middle and lower reaches of the river, including Hongshui River, Taolai River system, and many rivers such as the Heidaban River from Shandan Ciyaokou to the Gaotai, main stream of Heihe River, and Liyuan River, Nineteen high-risk “hot spots” in the Heihe River basin have been accurately identified. Severe pollution was mainly distributed in the risk sources around the water system and in the overlapping areas of roads along the river, bridges across the river, and companion sections of the water system. The risk of water pollution in the entire Heihe River basin was low and within a manageable range. [Conclusion] This evaluation index system can characterize the main problems of water pollution risk in inland river basins from multi-dimensional and multi-spatial perspectives to improve the evaluation index system of water pollution risk in these basins and the level of risk management in the entire river basin.

Abstract:[Objective] The impact of groundwater dynamics on the evolution of soil salinization and its mechanism were systematically investigated to provide a theoretical reference for the comprehensive treatment of saline-alkaline land. [Methods] Based on VOSviewer and Citespace visualization software, the relevant literature in the Web of Science core database (WoS) and China National Knowledge Infrastructure (CNKI) was used to analyse the number of articles issued and their countries and institution form. A quantitative and multivariate dynamic visualization analysis of domestic and international research in this field from 2000—2022 was carried out, starting from the amount, country institution and author of publications, and keyword clustering, and their changes over time. [Results] The research on the impact of groundwater dynamics on soil water salinity at home and abroad followed a fluctuating upward trend with China and the United States as the core, and the cooperation between China and the United States, Germany, Australia, and other countries was more closely linked. The core authors and institutions focused on the comprehensive utilization of saline-alkaline land and groundwater regulation, which has contributed greatly to the effective improvement of the quality of arable land. The English literature mainly covered the disciplines of water resources (26.18%) and environmental science and ecology (23.22%); the disciplines that accounted for the largest proportion of the Chinese literature were basic agricultural science (30.05%) and agronomy (27.76%). The focus has been gradually improved from single to diversified research and has been transformed from the basic theory of salinity to the comprehensive utilization of saline-alkaline land to improve quality and increase the efficiency of land use. Studies have actively responded to national strategic needs and have clarified the comprehensive utilization of saline-alkaline land to improve the quality of arable land. [Conclusion] This field is a hotspot for future research. Future research should focus on the following aspects: optimal allocation of water resources, establishment of a sound water resources development and management system, construction of a national cloud platform for comprehensive utilization of saline and alkaline land, strengthen the in-depth integration of information technology and water conservancy, and in-depth investigation of the mechanism of influence of groundwater regulation on the water and salt transport in the soil-air pocket. This research could provide new ideas and methods for the comprehensive utilization of saline land.

Abstract:[Objective] The present study was performed to develop a geological disaster susceptibility evaluation model for predicting frequent geological disasters in the Taishan area. The aim was to use the results of this susceptibility evaluation as reference for preventing and managing geological disasters in this area. [Methods] Our analyses focused on the Taishan area, employing a method in which the certainty factor (CF) model was coupled with a random forest (RF) model optimized using the particle swarm optimization (PSO) algorithm to evaluate the geological disaster susceptibility in the research area. This method uses the CF model to calculate the sensitivity values of the factors influencing geological disasters, which are then used as attribute values for model training. The PSO algorithm was introduced to optimize the parameters of the RF model, thereby improving the accuracy and precision of the model in predicting geological disasters. Eleven influencing factors, including slope, distance to roads, land-use type, and vegetation index, were selected. The Pearson correlation coefficient method and a multicollinearity check were used to screen and optimize these influencing factors. The precision of the trained model was evaluated using ROC and PR curves. [Results] Compared with those of the single SVR, single RF, and CF-PSO-SVR models, the CF-PSO-RF coupled model significantly improved the proportion of extremely-high-susceptibility areas by 10.55%, 10.04%, and 5.08%, respectively, increased the AUC values by 14%, 5.1%, and 1.7%, respectively, and enhanced the average precision (AP)accuracy by 11.7%, 4.4%, and 1.2%, respectively. The prediction results revealed that the regions with high and extremely high susceptibility to geological disasters were mainly located in the Taishan scenic area, Northern Daiyue District, and other regions with significant topographic relief and steep slopes, covering 28.05% of the area and encompassing 60.1% of the geological disaster points. In contrast, regions with low and very low susceptibility were primarily distributed in flat areas, such as construction and farm lands, accounting for 59.26% of the total area. [Conclusion] The accuracy of the CF-PSO-RF coupled model for disaster susceptibility evaluation was notably higher than that of the single models; further, its precision was superior to that of the CF-PSO-SVR model. These evaluation results are consistent with actual conditions.

Abstract:[Objective] The spatial autocorrelation patterns and influencing factors of soil and water loss and socio-economic development in Jilin Province were analyzed to provide a scientific basis for soil and water conservation and the green coordinated development in Jilin Province. [Methods] The analysis was based on the area of soil and water loss in various counties and cities in Jilin Province, combined with the social and economic statistics in the corresponding period. Tools including geographic information system (GIS), GeoDa, and ordinary least squares (OLS)linear regression models were used to analyze the spatial autocorrelation patterns of soil and water loss and socio-economic development and to identify the key influencing factors in Jilin Province from 2017 to 2021. [Results] ① The index of Moran’s I of soil and water loss in Jilin Province was positive with a minimum value of 0.254 6. Soil and water loss had an agglomeration effect in certain areas. The high-high agglomeration areas were primarily concentrated in the northwest of Jilin Province, and the low-low agglomeration areas were primarily concentrated in the southern region. ② The values of Moran’s I of urbanization rate, proportion of construction land, vegetation coverage area, and agricultural economic growth rate from the socio-economic indicators system of Jilin Province were relatively higher, and there were certain agglomeration characteristics in spatial. ③ The spatial autocorrelation analysis of soil and water loss and socio-economic reflected that Moran’s I values of “urbanization rate” and “forest area” were relatively large, and the spatial distribution of social type data was more concentrated compared to population and economic type data. ④ A high correlation was observed between the agricultural GDP, agricultural land use ratio, vegetation coverage ratio, and soil and water loss. The five-year average results of the correlation were 0.038, 0.003, and 0.154, respectively. [Conclusion] The soil and water loss, socio-economic development, and the double variables of soil and water loss and socio-economic development in Jilin Province have strong autocorrelation in space, respectively. Urbanization rate and vegetation coverage area were determined to have the most significant impact on soil and water loss among all the influencing factors.

Abstract:[Objective] The evaluation of carrying capacity of territorial space resources and environment in watersheds were studied based on multi scale fusion in order to provide scientific basis and reference for the sustainable development of the basin, and promote the coordinated development of resources and environment. [Methods] Using the Minjiang River basin as an example and considering the multifunctional characteristics and connotations of territorial spatial resources, we established a multi-scale evaluation system for territorial spatial resources and environmental carrying capacity. By applying an improved multiscale integration model, this study conducted a detailed micro-analysis of the evaluation results for research cross-sections from the years 2000, 2010, and 2020. [Results] ① Over the long term, the overall ecological carrying capacity (CC_E) of the basin has mostly been at a medium level. The living carrying capacity (CC_L) has generally been at a medium level or below, while the production carrying capacity (CC_P) has predominantly been at a very low level. Consequently, the comprehensive carrying capacity (CC_C) has mainly been at a low level, with no instances of a very high level. ② During the study period, the regions with low levels of all carrying capacities expanded. The expansion of CC_E mostly occurred in the middle and southeast of the basin; the expansion of CC_L occurred in the upper, middle, and lower reaches of the basin; the expansion of CC_P mostly occurred in the western and southern parts of Shuangliu and Renshou; and the expansion of CC_C mostly occurred in Wenchuan, Pujiang, and Jingyan. ③ The high CC_E and low CC_L and CC_P in the upper reaches of the Minjiang River can be attributed to the combined effects of topographical conditions and socioeconomic levels. In contrast, Chengdu’s central urban area has achieved outstanding levels of CC_L, CC_P, and CC_C, driven by high-quality socioeconomic development, and has maintained these levels over the long term. [Conclusion] The Minjiang River Basin exhibits significant regional differences in natural conditions and socioeconomic levels, resulting in varying levels of carrying capacity across different areas and hindering coordinated and balanced regional development. Persistently promoting high-quality development and leveraging the spillover and radiative effects of Chengdu City, the provincial capital, will help enhance the carrying capacity levels, reduce regional disparities, and drive overall coordinated development across the basin.

Abstract:[Objective] The impact of the expansion of Lycium barbarum planting land was predict scientifically in Zhongning County, Ningxia Hui Autonomous Region, in order to provide scientific and reliable suggestions for the future agricultural spatial layout and planting development of characteristic industries in the area. [Methods] Based on land survey data from 2005 to 2021 and considering the policy of “balancing in and out” of arable land, Zhongning County was taken as the research object and two constraint scenarios-one with and the other without the protection of permanent basic farmland-were set up. These were then used to simulate the future land use change of Zhongning County in 2025 and 2035 using the patch-generating land use simulation model (PLUS). Specifically, this model helped investigate the occupation of permanent basic farmland for L. barbarum cultivation in the future. [Results] According to the model, by 2035, under the with and without permanent basic farmland constraints scenarios, the area of land used for L. barbarum will grow by 59.81% and 98.48%, respectively. Most of the newly added L. chincnse will be around the original L. barbarum land, and the main townships with increased area will be concentrated in Mingsha Town and Dazhanchang Town. Moreover, the study showed that, under the scenario without permanent basic farmland constraints, the areas of permanent basic farmland in 2025 and 2035 will be encroached by 1,100.00 hm² and 2,386.67 hm², respectively, in which the risk of permanent basic farmland in the north-central region being encroached by L. barbarum land will be the highest. [Conclusion] It is therefore necessary to strengthen the regulation of the development of L. barbarum cultivation in high-risk townships and rationally plan existing and future land for “non-food” cultivation in order to coordinate the economic development of the area better with the protection of permanent basic farmland and promote the development of sustainable agriculture in the region.

Abstract:[Objective] The characteristics of soil and water loss and the effects of different soil and water conservation measures in Xi’an urban production and construction projects were investigated to provide scientific basis for improving the soil and water loss environment in Xi’an City and formulating more accurate and effective policies and measures. [Methods] Eighty-four production and construction projects in Xi’an City in 2022 were used as case studies, and a soil erosion evaluation system, which included three indicators such as water loss ratio, soil erosion ratio, and green space ratio, was constructed. The TOPSIS method was used to assess the water and soil loss risks associated with each project. [Results] ① The surface changes mainly shifted from rural homesteads, grasslands, idle land, and cultivated land to construction land. Among these changes, the conversion of rural homesteads constituted the primary form, accounting for approximately 70% of the total transfer area. ② Green space ratio increased in 83% of urban production and construction projects. Among the production and construction projects, there was a decreasing trend in the runoff losses observed in 61% of the cases in the order as follows: new real estate ＜ commercial services ＜ education and medical care ＜ municipal facilities ＜ urban village renovation projects. Approximately 54% of the production and construction projects successfully reduced soil erosion risks, with significant reductions observed in new real estate projects on cultivated land, grasslands, and idle land. But urban village renovation projects can increase regional soil erosion levels. The average reduction in water loss in all the projects was 3.58×10⁴ m³, and the average annual soil erosion decreased by 169.05 tons. ③ The risk of soil erosion in production and construction projects in Xi’an City were classified into four levels: high, medium, low, and very low. The projects classified as low and very low levels accounted for 69% of the total, with a particular focus on urban village renovation projects. All the projects involved in the occupation of grassland were classified as high risk. [Conclusion] Production and construction projects in Xi’an City have shown significant effectiveness in preventing soil and water erosion; however, they need to be improved further. In the future, it will be necessary to further strengthen the management of soil and water erosion risks in these projects.

Abstract:[Objective] The spatial and temporal properties of vegetation cover in the Hengduan Mountains and the variables that influence them was investigated in order to provide the scientific basis to understand this topic. [Methods] The Theil-Sen trend analysis and Mann-Kendall test were used to analyse the inter-monthly and inter-annual variability of the normalized difference vegetation index (NDVI) in the Hengduan mountains from 2002 to 2022, as well as spatially overall. Using partial correlation analysis, the effects of temperature and precipitation on vegetation cover were examined. Finally, the impact of human activities on vegetation cover was explored combining with land cover data. [Results] ① The NDVI in the Hengduan mountains area showed an increasing fluctuating trend over 21 years, at its lowest in March and highest in September. ② The spatial vegetation cover increased by 83.78%, primarily in the southeastern, southwestern, and northern regions, and decreased by 15.87%, primarily in the central, southern, northwestern, and northeastern regions, with a good trend of increasing vegetation cover throughout the study area. ③ The NDVI showed a strong positive correlation with both temperature and precipitation on the monthly scale, while on the annual scale, it showed a weak negative correlation with precipitation and a positive correlation with temperature. ④ During the 21-year period, there was a significant decrease in the area of agricultural land, a large increase in the area of forestland, a slight decrease in the area of grassland, and little change in the areas of urban and built-up land and water. One of the reasons for the increase in the NDVI throughout the 21-year period in the Hengduan Mountains region is the large increase in forested land area. [Conclusion] There were significant temporal and spatial variations in vegetation cover in the Hengduan Mountains. Temperature and precipitation influenced both vegetation cover and land use as driving factors of vegetation cover change.

Abstract:[Objective] The value of ecological products was calculated scientifically and the transformation path of “Two Mountains” (lucid waters and lush mountains are invaluable assets) was explored in order to provide theoretical support for the practical effect of the “Two Mountains” theory and promote the construction of an ecological civilization. [Methods] Based on the theory of “Two Mountains,” and taking Guizhou Province as the research object, this paper constructed an index system of ecological product value accounting, measured the ecological product value using the gross ecosystem production (GEP) accounting method, and assessed the effect of the “Two Mountains” transformation. [Results] ① From 2017 to 2021, the GEP of Guizhou province showed an upward trend, which was 2.08~2.54 times the GDP of the same year, but the growth rate of the GEP was lower than that of the GDP. The GEP per unit area was 1.96×10⁷ yuan/m² to 2.32×10⁷ yuan/m², and the per capita GEP was 90 500 yuan/m² to 1.06×10⁶ yuan/m². The results showed that the transformation of environmental resource protection, sustainable utilization, and the economic growth mode has achieved certain results. ② The value of ecological material supply products presented an upward trend with a range of 18.66%; the value of agricultural products was the highest and the value of fishery products was the lowest. The results showed that Guizhou is still a province with agriculture as its main focus, and planting is the main aspect of the agricultural industry. ③ The total value of ecological regulation service products showed an increasing trend, with an increasing range of 8.34%, accounting for 60.30%—66.35% of the GEP. The value of climate regulation was the highest, and the value of water quality purification was the lowest. This shows that a superior ecological environment and high forest coverage are important climate regulators and ecological barriers. ④ The value of eco-cultural service products (ECVs) showed an increasing trend, with an increasing range of 45.71%, accounting for 20.56%—27.65% of the GEP. ⑤ The transformation value of “Two mountains” showed an increasing trend of dynamic change, with an increasing range of 39.37%, accounting for 82.40%—92.40% of the GDP. This shows that the “Two Mountains” transformation has achieved certain results, and the contribution of ECVs has been high. However, Guizhou Province needs to further enhance the effectiveness and contribution of eco-material product value and eco-cultural product value in the process of the “Two Mountains” transformation. Based on the research results, this paper refines the path to promoting the “Two Mountains” transformation. [Conclusion] The protection effect of natural resources and ecological environment in Guizhou Province is increasing, the ecosystem has strong ecological regulation function, and climate regulation is the main type of ecological regulation; The value of non-physical products is dominant, and the value of physical products is relatively small. The transformation effect of “Two Mountains” is increasing year by year, however, it is necessary to further improve the contribution of the value of ecological material products and ecological culture products to the transformation of “Two mountains”.

Abstract:[Objective] The water poverty in China’s provinces (cities) was measured and social network analysis was conducted in order to provide a decision-making basis for alleviating China’s water poverty dilemma. [Methods] The entropy weight method and social network analysis were employed to measure and analyze the spatial correlation effects of water poverty in various Chinese provinces (cities) from 2010 to 2021. [Results] ① The water poverty index of Chinese provinces has shown an overall upward trend during the inspection period, and the degree of water poverty has gradually decreased. However, the spatial non-equilibrium characteristics remain quite evident. ② The provincial water poverty network exhibits significant spatial correlation and complex structural forms as a whole, with all regions interconnected; however, the degree of closeness of this correlation is not high. ③ According to the block model analysis results, 5 provinces (cities) including Beijing and Tianjin are classified as the “net beneficiary” group, 13 provinces (cities) including Hunan and Hainan as the “net spillover” group, 4 provinces (cities) including Guangdong and Chongqing as the “two-way spillover” group, and 9 provinces (cities) including Inner Mongolia and Heilongjiang as the “broker” group. In addition, the relationships within the plates are sparse, whereas the connections between the plates are strong. ④ Analysis of the core-edge density shows that the number of core areas fluctuates frequently, while the number of edge areas initially increases and then decreases. [Conclusion] The State should develop a comprehensive understanding of the spatial correlation and network structure characteristics of the Water Poverty Index, formulate and implement regionally differentiated policies and strategies, promote coordinated development, give full play to the roles of the government and market, effectively address the challenges of water poverty, and enhance water security.

Abstract:[Objective] The vulnerability and obstacle factors of water resources in Wuhan City were explored to further clarify the characteristics and influencing mechanism of water resources system, therefore to provide a basis for regional water resources management and efficient utilization. [Methods] Combined with the current situation of water resources in Wuhan City, 12 indicators were selected to construct a water resource vulnerability assessment system based on a pressure-state-response model. The entropy weight method was used to calculate the indicator weight, and the set pair analysis method was used to assess water resource vulnerability. On this basis, an obstacle degree model was applied to identify obstacles of water resource vulnerability in Wuhan City. [Results] The overall vulnerability of water resources in Wuhan City showed a gradually decreasing trend from 2013 to 2022, and the vulnerability level decreased from middle to micro vulnerability. From the perspective of each subsystem, the vulnerability of water resources in the pressure subsystem gradually decreased, whereas the state and response system vulnerability levels showed a fluctuating decrease. The main obstacles affecting the vulnerability of water resources are water consumption per 10 000 yuan of GDP, water consumption per 10 000 yuan of industrial added value, compliance rate of river water quality, development and utilization rate of water resources, and the centralized treatment rate of sewage. The order of obstacle degree was pressure > state > response. [Conclusion] Although water resources are greatly influenced by human activities, they can provide important support for economic and social development in Wuhan City. The vulnerability of regional water resources could be effectively reduced and the supply-demand contradiction of water resources alleviated by continuously optimizing the allocation of water resources, accelerating the upgrading of industrial structures, improving the level of sewage treatment, and applying technological innovation.

Abstract:[Objective] The coupling and coordination status of agricultural ecological security and food security was explored in order to provide decision-making reference for improving both, individually, and their coordinated development in the Yangtze River economic belt. [Methods] Taking 11 provinces (cities) in the Yangtze River economic belt as the research areas, the entropy weight method, comprehensive index model, coupling degree model, coupling coordination degree model, grey correlation degree model, grey prediction model, and exponential smoothing model were used to quantitatively analyze the coupling coordination level, coupling coordination development level, influencing factors, and future trends of agricultural ecological security and food security. [Results] ① From 2002 to 2022, the comprehensive index of agricultural ecological security and food security in most provinces of the Yangtze River economic belt showed a significant fluctuation trend. The gap in the level of comprehensive index of agricultural ecological security and food security between provinces first narrowed and then expanded, and the overall gap between samples was not significant. ② From a temporal perspective, the coupling coordination degree of various provinces in the Yangtze River economic belt fluctuated significantly from 2002 to 2022, showing an overall upward trend, with most coupling coordination levels rising to a more optimal level. Regarding spatial dimension, the overall distribution characteristics show relatively low upstream, low midstream, and high downstream trends, as well as significant regional differences. ③ Agricultural ecological security and food security are a coupled and interactive system, and both the subsystems of them influence the degree of coupling coordination. The impact of the provincial grain security subsystem in the Yangtze River economic belt on the coupling coordination degree is higher. ④ Using the exponential smoothing method to predict the coupling coordination degree of provinces in the Yangtze River economic belt for the next five years, different provinces show different trends, with both upward and slightly downward trends. [Conclusion] Provinces in the Yangtze River economic belt should adapt to local conditions, further enhance the synergy and linkage of internal and external factors on the basis of filling in the shortcomings and weaknesses of the subsystems, and ultimately achieve the benign coordinated development of the two.

Abstract:[Objective] The impact of comprehensive flood control projects on the improvement of river happiness was analyzed in order to improve the construction level of happy rivers, and provide a theoretical basis for the evaluation and construction of happy rivers in Shandong Province. [Methods] Taking Xiaoqing River basin as the research object, a multi-level happy river evaluation index system, based on the “goal layer-criteria layer-index layer” was established, including 20 indices from 5 criteria layers: water safety, water resources, water environment, water ecology, and water culture. It also evaluated the state of well-being and identified the main obstacles that hindered the construction of happy rivers. A combination weighting method based on the analytic hierarchy process and reverse entropy weight method was applied to determine the indices weights at urban and rural sections and identify the main obstacles affecting the construction of happy rivers through the obstacle degree. [Results] ① Watershed area retention had the highest weight in the urban section, and the percentage of levee flood defense standard compliance had the highest weight in the rural section. ② Before the construction of the flood control project, the happiness levels of the urban and rural sections were generally lower. After construction, the happiness levels in both sections improved; happiness was maintained in the urban section and improved to a generally higher level in the rural section. ③ In the criteria layer, the main obstacle affecting the construction of happy rivers in the urban section focused on the water resource layer, and the main obstacle affecting the rural section focused on the water safety, water resources, and water culture layers. [Conclusion] To improve the happiness level of rivers, it is necessary to enhance the water supply capacity through reservoir storage and water diversion projects, maintain a smooth flow in flood channels, and stabilize river courses to ensure flood control safety.

Abstract:[Objective] The response characteristics and demand changes of soil and microbial nutrients to shrub encroachment in Loess Plateau were investigated to provide reference for grassland resource management in the Loess Plateau. [Methods] The no-shrub encroachment grassland, subshrub (Artemisia sacrorum) encroachment grassland, and shrub (Caragana brachypoda) encroachment grassland in the Yunwu Mountain National Nature Reserve and measured the physicochemical properties of soil and activities of five enzymes involved in soil carbon, nitrogen, and phosphorus cycles. Afterward, we analyzed the effects of subshrub and shrub encroachment on soil nutrient content, enzyme activities, and stoichiometric ratios. [Results] Subshrub and shrub encroachment increased the content of soil water and nutrients and the activities of carbon, nitrogen, and phosphorus cycling enzymes. Soil microbial nutrient demands were not consistent across soil layers: in the 0—15 cm soil layer, soil microorganisms in the subshrub and shrub encroachment grassland had a higher demand for phosphorus element, whereas in the 15—30 cm soil layer, soil microorganisms had a higher demand for carbon element. Redundancy analysis showed that soil available nutrients were the key factors affecting soil enzyme activity and stoichiometric ratio. [Conclusion] Subshrub and shrub encroachment had positive effects on soil nutrient content and enzyme activity of enclosed grassland in Loess Plateau, and soil microorganisms under the subshrub and shrub encroachment grassland met their nutrient demands by changing the relative input of carbon, nitrogen, and phosphorus cycling enzymes; therefore, the trend of subshrub and shrub expansion in the region need to be further strengthened in the future. To maintain the stability of grassland ecosystem in Loess Plateau, corresponding regulatory measures need to be explored urgently.

Abstract:[Objective] The impact of reed-based exogenous carbon on soil properties and organic carbon stability was investigated to provide theoretical insights into the application of reed resource materials for soil improvement. [Methods] A 60-day soil culture test was conducted for the application of various exogenous carbon materials, including reed aerobic compost (compost T₁ conditioned with biochar and compost T₂ conditioned with sediment and biochar), straw (RS), and biochar (RB). The effects of different exogenous carbon sources and amounts (5%, 10%, and 15%) were analyzed on the physicochemical properties, enzyme activities, and organic carbon mineralization of the soil. [Results] The application of exogenous carbon influenced the soil nutrient content, with the soil organic carbon content in the experimental group increasing significantly by 28.0%—64.2% compared to that in the control group (p<0.05) at the beginning of the culture. Compared with the initial stage, the organic carbon content of the soil supplemented with biochar and compost at final stage was significantly reduced by 15.5%—23.5%, whereas the total nitrogen content of the soil at final stage decreased by 20.0%—69.1%. The concentrations of β-glucosidase and dehydrogenase increased following the addition of exogenous carbon, with the most significant effect observed for biochar and compost. The β-glucosidase and dehydrogenase contents in the soil presented highly significant positive correlations with the soil bulk density, carbon source content, and total nitrogen (p＜0.01). The cumulative mineralization of organic carbon in the soil following the addition of exogenous carbon during the culture experiment exhibited first-order kinetics, while the soil organic carbon mineralization in the straw and biochar treatment groups was 652.9—758.2 mg/kg, which was significantly higher than that in the control group (532.8 mg/kg) and T2 composting (598.3—623.7 mg/kg) treatments. The amount of exogenous carbon added significantly influenced the soil organic carbon mineralization. [Conclusion] The addition of reed-based exogenous carbon improved soil physical and chemical properties and significantly enhanced enzyme activities. The excitation effect of reed straw on soil organic carbon mineralization was significantly greater than that of biochar and compost.

Abstract:[Objective] Soil CO₂ production potential of different vegetation types in response to temperature change was analyzed in order to provide the basis for accurate estimation of CO₂ production and greenhouse gas emissions. [Methods] A simulated culture experiment was conducted for 120 days for three different types of wetland soil (Nelumbo nucifera, Phragmites australis and open water), and the treatment was set at 15, 25, and 35 ℃ to observe the difference in the CO₂ production potential of the wetland soil of different vegetation types and evaluate their response to temperature change. [Results] The fastest soil CO₂ production rate among the different vegetation types in East Taihu Lake was recorded in the 35 ℃ culture treatment. Under the culture temperature of 35 ℃, the CO₂ production rate of P. australis and open water surface increased with an increase in dissolved organic carbon (DOC) but that of the rest were negatively correlated. The maximum CO₂ production potential of N. nucifera and P. australis soil was in the order as follows: 35 ℃ ＞ 15 ℃ ＞ 25 ℃ and that of open water surface was 15 ℃ ＞ 25 ℃ ＞ 35 ℃. The CO₂ production potential of N. nucifera and P. australis wetlands was positively correlated with culture temperature, whereas that of the open water surface was significantly negatively correlated. Comparising all of the temperature sensitivity coefficient Q₁₀ values, it was found that only N. nucifera soil temperature rise Q₁₀＞ temperature drop Q₁₀. [Conclusion] High temperature can accelerate CO₂ production rate and increase DOC change in different vegetation types. Regarding the CO₂ production potential of soil with the same temperature and different vegetation, it was found that P. australis and open water surface were more sensitive to cooling. The greenhouse gas production of wetland plants and the soil was greatly affected by external temperature; therefore, more attention should be paid to future urban water ecological management.

Abstract:[Objective] The relative enzyme activity and kinetic parameters of typical forest soil in loess hilly region were analyzed and the driving factors of soil enzyme activity characteristics were revealed in order to provide theoretical basis for the construction and improvement of regional artificial forests. [Methods] Coniferous forest (Pinus tabulaeformis), broad-leaved forest (Quercus acutissima), and mixed forest (P. tabulaeformis Q. acutissima mixed forest) in loess hilly region were selected as the research objects. Through field soil sampling and laboratory incubation analysis, soil physical and chemical properties and specific soil carbon, nitrogen, phosphorus transformation-linked enzyme activities 〔β-1,4-Glucosidase (BG), N-acety-β-glucosaminidase (NAG)〕, L-leucine aminopeptidase (LAP), and alkaline phosphatase (ALP) and their kinetic parameters 〔maximum reaction rate (V_max), Michaelis constant (K_m), and catalytic efficiency (K_cat)〕 were measured. [Results] ① The soil bulk density (BD), pH value, and enzyme activities of BG, LAP, and ALP per unit of organic carbon all increased with soil depth; however, the soil water content (SWC) and soil organic carbon (SOC) content decreased with soil depth. The highest pH value was in the coniferous forest, and the ammonium nitrogen (NH₄⁺-N) and total phosphorus (TP) contents were in the order of broad-leaved forest＞mixed forest＞coniferous forest. ② The average (comprehensive) soil enzyme activities and K_cat value were in the order of mixed forest＞coniferous forest＞broad-leaved forest. The K_m value were in the order of mixed forest＞coniferous forest＞broad-leaved forest. ③ The specific activities of the four enzymes related to carbon, nitrogen, and phosphorus transformation were significantly negatively correlated with NH₄⁺-N, nitrate nitrogen (NO₃^--N), available phosphorus (AP), and SOC content, whereas the specific activities of BG, NAG, and ALP per unit of organic carbon were significantly positively correlated with pH value. Redundancy analysis showed that SOC content had significant influence on enzymatic reaction parameters in both coniferous forest and broad-leaved forest (p＜0.01). The main factors affecting the specific enzyme activities and kinetic parameters in mixed forest were SOC (p＜0.01) and TP (p＜0.05) content. [Conclusion] The soil enzyme activities per unit of organic carbon and K_cat of mixed forest were higher than those of coniferous forest and broad-leaved forest in loess hill region, indicating that the enzyme catalytic ability in mixed forest was higher than those in coniferous forest and broad-leaved forest. Therefore, mixed forest should be given priority consideration in artificial afforestation to improve soil quality.

Abstract:[Objective] The impact of tunnel construction on soil organic carbon content and enzyme activity in the Qinghai-Xizang Plateau was researched in order to provide a theoretical reference for elucidating the impact of tunnel construction on the ecological environment. [Methods] Based on the construction of a tunnel project on the Qinghai-Xizang Plateau, fixed monitoring plots with a radius of 10 m were set up in the impact area and control area of tunnel construction to study the short-term effects of tunnel construction on surface soil organic carbon content and enzyme activity. [Results] After one year of tunnel construction, the soil organic carbon content, easily oxidizable organic carbon content, and soluble organic carbon content in the tunnel-impact area were determined to be 76.84, 25.90, and 3.15 g/kg, respectively, while that of the control area was 52.91, 15.60, and 3.18 g/kg, respectively, whereas that after three years of tunnel construction was 92.63, 28.65, and 3.41 g/kg in the impact area respectively, and 94.81, 23.11, and 3.34 g/kg in the control area, respectively. The differences were not significant (p＞0.05), indicating that tunnel construction has no impact on soil organic carbon and component content in the short term. The activities of β-glucosidase and catalase in the soil of the tunnel-affected area demonstrated no significant differences compared to the control area after one year and three years of construction (p＞0.05), while the activity of polyphenol oxidase in the tunnel-impact area decreased significantly after one year of construction (p=0.02). However, after three years of construction, there was no significant difference in polyphenol oxidase activity between the tunnel-impact area and the control area (p＞0.05), indicating that tunnel construction had no significant effect on soil enzyme activity. [Conclusion] Tunnel construction has no significant impact on soil organic carbon and its component content, as well as enzyme activity in the short term. This is primarily because the tunnel construction process has no significant impact on soil microbial processes, soil nutrients, and input and output of soil organic carbon, while the long-term impact needs further research.

Abstract:[Objective] The carbon sink function of terraces and their characteristics were analyzed and discussed to provide a scientific reference for clarifying the carbon sink function, consolidating and enhancing the carbon sink capacity of ecosystems, and researching and compiling a carbon sink methodology for terraces. [Methods] Terraces with the operational ages of 1—7 a (T₅), 8—12 a (T₁₀), 13—17 a (T₁₅), 18—22 a (T₂₀), and 23—27 a (T₂₅) were selected at Wuqi County, Shaanxi Province in the loess hilly and gully region. Slope croplands without soil and water conservation measures were selected for baseline comparison to study the capabilities of terraces in terms of carbon preservation, emission reduction, and carbon sequestration across different years. [Results] ① After the transformation of sloped croplands into terraces, an increase was observed in carbon preservation, emission reduction, and carbon sequestration. Annual carbon preservation, emission reduction, and carbon sequestration (0—100 cm) were 0.26, 0.05 and 1.36 t/hm² respectively. ② Each soil layer of the terraces contributed certain benefits; the carbon sequestration benefits of the surface (0—40 cm) and deep (40—100 cm) soil layers accounted for 61.50% and 38.50% of the entire soil layer, respectively. ③ The benefits of the terrace surface soil significantly increased with the increase in the operation year of the terrace, while the benefits of deep soil were slightly improved but remained stable on the whole. The rate of carbon sequestration in the surface soil increased from 16.30% at T₅ to 51.34% at T₂₅ and that in the deep soil increased from 14.00% at T₅ to 23.66% at T₂₅. [Conclusion] The terraces in the loess hilly and gully regions exhibited significant carbon sink functions, including carbon preservation, emission reduction, and carbon sequestration. The proportion of carbon sequestration capacity was the largest within 27 years of terrace operation, and the increase in the surface soil was more significant. The proportion of carbon preservation in the carbon sink capacity of terraces gradually increases with an increase in terrace operation years.

Abstract:[Objective] The effects of different management intensities on soil physicochemical properties and soil quality were analyzed to provide a scientific basis for the scientific management and nutrient management of Phyllostachys praecox forests. [Methods] Based on the analysis of soil physicochemical properties in P. praecox plantations under various management intensities in Huangshan District, Anhui Province, a minimum dataset was established through principal component analysis, and the soil quality in P. praecox plantations under different management intensities was analyzed. [Results] Significant differences were observed in the soil physicochemical properties under different management intensities. The bulk density was significantly lower in mid-intensity management than in high-intensity and extensive management in the 0—10 cm soil layer. The soil water contents in mid- and high-intensity management were significantly lower than those in extensive management. In the 0—10 cm soil layer, the value of soil pH value was ranked in the order of high-intensity management (4.12) ＞extensive management (4.01) ＞mid-intensity management (3.97). The soil organic carbon (24.82 g/kg) and total nitrogen (1.67 g/kg) in mid-intensity management were significantly higher than those in extensive management (18.64, 1.35 g/kg) and high-intensity management (17.39, 1.25 g/kg). The soil total phosphorus (0.53, 0.49 g/kg) was significantly higher in mid- and high-intensity management than in extensive management (0.27 g/kg). The ranges of C/P (30.99—53.40) and N/P (2.77—3.60) in mid-and high-intensity were lower than those in extensive management 〔(64.82—78.96) and (5.20—5.56)〕, and the average value of soil C/N in three different management intensities ranged from 10.95 to 14.68. In the 0—10 cm soil layer, the soil quality indices in the different management intensities were ranked in the order of extensive management (0.42) ＞mid-intensity management (0.36) ＞high-intensity management (0.31), where the soil quality index decreased with the deepening of the soil layer. [Conclusion] A strong acidic soil environment was determined not to be conducive to the growth of bamboo. Soil water holding capacity and water conservation capacity of mid-intensity management were determined to be better. Soil fertility was observed to be lower with the strengthening of management intensity, which is not conducive to the maintenance of soil quality.

Abstract:[Objective] The changes of land use and carbon storage under different scenarios were analyzed to provide the scientific bases were provided for optimizing of land use pattern and formulating protection policies in Hainan Tropical Rainforest National Park. [Methods] Based on the land use data of Hainan Tropical Rainforest National Park in 2001, 2011 and 2021, and the PLUS and InVEST models, the changes of land use and carbon storage in 2001—2021 and 2030 under different scenarios were analyzed and predicted, respectively. [Results] ① From 2001 to 2021, the cultivated lands, grassland and water decreased continually, while the forest land and construction land gradually expanded in Hainan Tropical Rainforest National Park. And the forest land increased by 561.19 km² in 20 years. The predicting results of land use changes under natural development scenario and farmland protection scenario in 2030 were similar but were much different with the results of ecological protection scenario. ② In 2001, 2011, and 2021, the carbon storage of Hainan Tropical Rainforest National Park was 8.72×10⁷ t，9.22×10⁷ t，and 9.13×10⁷ t, respectively. In 2030, the carbon storage of Hainan Tropical Rainforest National Park would be 9.04×10⁷ t under natural development scenario, 9.12×10⁷ t under farmland protection scenario, 9.13×10⁷ t under ecological protection scenario. These results indicating that the ecological protection measures could improve the ability of carbon storage in Hainan Tropical Rainforest National Park. [Conclusion] The change of carbon storage was highly consistent with the change of land use, and land use change could affect the pattern of carbon storage in Hainan Tropical Rainforest National Park.

Abstract:[Objective] Spatial network characteristics and driving forces of net carbon sequestration in the Yangtze River economic belt (YREB) were analyzed to provide a scientific reference for promoting coordinated carbon emission reduction, supporting the achievement of “dual carbon” goals and regional coordinated development. [Methods] A spatial association network of carbon sinks in the YREB was constructed at the municipal level using a modified gravity model. Social network analysis was then applied to examine the network’s characteristics and driving factors. [Results] ① From 2001 to 2021, total carbon emissions in the YREB exhibited an increasing trend, with a spatial distribution pattern of higher and lower emissions in the east and west, respectively. Conversely, total carbon sinks followed a fluctuating upward trend, showing a pattern of higher sinks in the west and lower in the east. Net carbon sinks have continuously declined, with a similar west-east gradient. ② The carbon sink network in the YREB showed significant spatial correlation, forming a complex dense in the east and sparse in the west network pattern, with Chongqing and Shanghai City emerging as dual-core nodes. The regional network exhibited high centrality, with cities such as Shanghai and Chongqing City playing key roles. The network’s overall structure demonstrated low stability. ③ Cities were categorized into four groups based on their roles within the network: net exporters, bidirectional exchanges, brokers, and net beneficiaries. Interblock spillover effects were more pronounced than intra-block associations. ④ The primary driving forces behind the spatial association network of carbon sinks were economic development, industrial structure upgrades, energy consumption intensity, and land-use patterns. [Conclusion] In the future, it is essential to consider the spatial network dynamics of net carbon sinks across cities, leveraging complementary strengths to maximize emission reduction benefits.

Abstract:[Objective] The carbon storage effect and the driving factors in the transformation of productive-living-ecological space in the Xiamen-Zhangzhou-Quanzhou metropolitan area were analyzed in order to provide scientific reference for the high-quality development of the Xiamen-Zhangzhou-Quanzhou metropolitan area under new circumstances. [Methods] Spatial analysis, InVEST, and GeoDetector were comprehensively utilized to reveal the transformation characteristics of the productive-living-ecological space, carbon storage effect, and main influencing factors in the Xiamen-Zhangzhou-Quanzhou metropolitan area. [Results] ① From 2000 to 2020, the living space in the Xiamen-Zhangzhou-Quanzhou metropolitan area continued to expand, while the production and ecological spaces continued to shrink. The transformation of the production-living-ecological space primarily manifested in the shift from agricultural production, woodland ecological, and grassland ecological spaces to industrial production and urban living spaces. ② Over the past 20 years, carbon storage in the Xiamen-Zhangzhou-Quanzhou metropolitan area decreased by 1.57×10⁷ t. The shift of forest ecological space to industrial production (34.75%) and grassland ecological (16.73%) spaces, as well as the shift of agricultural production space to industrial production (12.92%) and urban living (7.63%) spaces, were significant reasons for the decrease in carbon storage. The spatial distribution of carbon storage exhibited a decreasing trend from the hilly mountains in the west to the coastal plains in the east. ③ The natural environment and social economy emerged as the primary factors influencing regional carbon storage, with location conditions exerting minimal influence. Notably, the gross output value of the secondary and tertiary industries, along with slope consistently played significant roles in carbon storage in the Xiamen-Zhangzhou-Quanzhou metropolitan area. Moreover, the interaction among all factors significantly amplified their impact on carbon storage. [Conclusion] Future efforts should prioritize the protection of ecological space and promote the region’s role as a leading economic growth pole to achieve the coordinated progress of carbon emission reduction and economic development in the Xiamen-Zhangzhou-Quanzhou metropolitan area.

Abstract:[Objective] Under the “double carbon” goal, the impact of land use on carbon emission, absorption, and balance was examined to provide a basis for national spatial planning. [Methods] The Chengdu-Chongqing economic zone was taken as the study area, based on land use and socio-economic data, and the coefficient method was adopted to measure the carbon balance of the study area from years 2000 to 2022. The study then explored the differences in the spatial and temporal patterns of the area and conducted carbon balance zoning of the processed results from multiple perspectives using the economic contribution rate and ecological carrying capacity coefficient. Lastly, a targeted strategy was proposed. [Results] ① Carbon emissions generally showed an upward trend, and cropland and construction land were the most important sources of carbon. These land types were spatially distributed mainly in the Chengdu Plain and Chongqing metropolitan areas of the study area. ② The total amount of carbon sequestration showed an upward trend, and the main source of carbon sinks was forest land, which was spatially distributed mainly in the mountainous areas around the study area. ③ Total net carbon emissions increased by 273%. The number of counties achieving carbon balance reduced from 23 to 10. ④ Based on carbon balance analysis, indicators of net carbon emissions, and economic contribution rate, among others, high-quality agricultural production areas were classified as low-carbon development zones, densely populated and narrowly developed core areas as carbon-intensity control zones, traditional industrial areas as high-carbon optimization zones, and ecological barrier zones as carbon sink functional zones. [Conclusion] The spatial and temporal differences in carbon emissions in the Chendu-Chongqing ecomic zone had corresponding regularities, and the carbon absorption space were more stable. Therefore, to promote the low-carbon and sustainable development of the economic zone, the land resource utilization structure can be further adjusted in a more refined way according to the land zoning optimization plan.

Abstract:[Objective] The measurement of land space use efficiency and comprehensive spatial zoning in Yunnan Province were studied, considering carbon neutrality, provide a reference for proposing differentiated low-carbon and high-efficiency land space development strategies. [Methods] Using 2020 panel data of 16 municipal units in Yunnan Province, the spatial utilization efficiency of the national territory under the low-carbon perspective were measured based on the non-expected output super-efficiency SBM model, and comprehensive zoning were performed considering the carbon efficiency index; subsequently, optimization suggestions for each zone are put forward. [Results] ① The carbon emission in Yunnan Province in 2020 was 1.23×10⁸ tonnes, with production-space-related emissions accounting for a much larger proportion than living-space-related emissions: the former was almost 31 times as much as the latter. Further, carbon absorption was 1.40×10⁷ tonnes, which is only one-tenth of the carbon emission. ② In 2020, the land space utilization efficiency of Yunnan Province was only 0.628, showing a spatial distribution pattern that is higher in central and northwestern Yunnan, and lower in eastern and southwestern Yunnan. Specifically, only Xishuangbanna, Diqing and Yuxi reached high efficiency utilization, with the maximum efficiency of 1.43, while Zhaotong had the lowest utilization efficiency of 0.49. ③ Based on the land space utilization efficiency and the carbon efficiency index, 7 comprehensive zones-Low carbon retention-High efficiency, Carbon sink function-High efficiency, Carbon sink function-Moderate efficiency, Carbon sink function-Low efficiency, Carbon intensity control-High efficiency, Carbon intensity control-Moderate efficiency, and High carbon optimization-Low efficiency-are derived, and a differentiated governance strategy for each zone is put forward. [Conclusion] At present, carbon absorption in Yunnan Province is far from enough to offset carbon emissions, and the overall performance is carbon source. The utilization of territorial space is still relatively extensive, and there is great potential to improve utilization efficiency. The distribution of territorial space utilization efficiency has obvious regional imbalance, and attention should be paid to the formulation of low-carbon development and efficient utilization strategies for territorial space.

Abstract:[Objective] The dynamic changes in vegetation carbon use efficiency (CUE) and its relationship with hydrothermal factors in the Inner Mongolia Autonomous Region was investigated to provide a scientific basis for evaluating vegetation carbon sequestration capacity. [Methods] Vegetation CUE was calculated using MOD17A2H data. Trend analysis, Hurst index, and correlation analysis were employed to investigate the spatiotemporal dynamics of vegetation CUE from 2000 to 2022 and the influence of hydrothermal factors on vegetation CUE. [Results] ① During 2000—2022, vegetation CUE increased significantly, with a growth rate of 0.012 per decade (p<0.05). The CUE values of key ecological functional areas in Inner Mongolia followed this order: Daxinganling and Xiaoxinganling Mountains > Hulun Buir > Hunshandake > Khorchin > Northern Yinshan. ② The spatial distribution of vegetation CUE in Inner Mongolia was higher in the west and lower in the east during the growing season, with an average annual value of 0.60. Among the key ecological functional areas, the highest vegetation CUE was observed in Hunshandake, while the lowest was in Khorchin. ③ Vegetation CUE exhibited an increasing trend in 83.53% of the study area, and this trend remained constant during the growing season. However, 72.14% of the study area would experience a decreasing trend in vegetation CUE in the future, with a higher proportion of key ecological functional areas showing a declining trend compared to those with an increasing trend. ④ Overall, vegetation CUE was negatively correlated with average temperature and positively correlated with cumulative precipitation and average soil moisture, with a stronger correlation observed with cumulative precipitation during the growing season. In contrast, vegetation CUE had a stronger correlation with average temperature than with cumulative precipitation and average soil moisture in Khorchin. [Conclusion] The carbon sequestration capacity of vegetation in Inner Mongolia increased significantly from 2000 to 2022 but would decline in the future. Precipitation was the main factor affecting changes in vegetation CUE in key ecological functional areas, while temperature was the dominant influencing factor in Khorchin.

Abstract:[Objective] The changes in land cover and carbon stock of the Hangzhou Chengxi Sci-tech Innovation Corridor through high-resolution remote sensing images were analyzed and the development trend of carbon stock under the constraints of the “three zones and three lines” achievements was predicted to provide scientific basis for the optimization of national land space and ecological development of new urban centers. [Methods] Based on four periods of land cover data from 2010, 2015, 2020, and 2023, the GeoSoS-FLUS model was used to simulate both past and future changes in land cover under five different scenarios: the natural growth, extreme construction and development, extreme agricultural production, ecological function services, and urban-rural integration development scenarios up to the year 2035. The model was used as a framework to calculate the changes in carbon stock under the simulated scenarios from 2010 to 2023 and from 2023 to 2035, respectively. [Results] ① The carbon stock of Chengxi Sci-tech Innovation Corridor showed an increasing trend from 2010 to 2023, with a total change of 1 720.69 t, where the carbon stock of vegetation, soil, and water increased to approximately 913.67 t, 566.18 t, and 240.84 t, respectively. ② The internal type transformation of cultivated land resulted in a decrease of 119.33 t in soil carbon stock, while the internal type transformation of forest land accounted for 39.50% of the total change in carbon stock. ③ In the natural growth and ecological function services scenarios, forest land growth was relatively significant, while in the extreme construction and development and extreme agricultural production scenarios, the land cover types were more stable. In the urban-rural integration development scenario, through reasonable replacement between cultivated land, forest land, grassland, and other land cover types, other land cover types obtained greater development space. ④ During 2023—2035, carbon stock will rise by 898.74 t under the natural growth scenario, 538.58 t under the extreme construction and development scenario, 517.45 t under the extreme agricultural production scenario, 813.09 t under the ecological function services scenario, and 356.91 t under the urban-rural integration development scenario. [Conclusion] Development under the constraint of control lines could effectively guarantee the carbon sequestration capacity of cities. Reasonable transformation of land cover types and internal structural adjustments can provide more space for the development of new urban centers.

Abstract:[Objective] Under the goal of carbon neutrality, we explore the spatial and temporal evolution of the function of productional-living-ecological (P-L-E) in Hunan Province and its distribution pattern of carbon emissions in the future in order to provide strategy-making references for carbon emission reduction in all provinces of the country. [Methods] Based on the P-L-E function evaluation prediction and productional-living-ecological carbon emission distribution measurement models, combined with various data on the regional P-L-E function and the spatial-temporal differentiation law, this study explored the spatial-temporal relationship between the function of P-L-E and the carbon emissions in Hunan Province and the planning strategy of the distribution pattern of carbon emissions in the future. [Results] ① From 2000 to 2020, the spatial and temporal differentiation of P-L-E in counties of Hunan Province was obvious, and the spatial pattern of the ecological function was strong and weak in the west and east, respectively which showed a trend of first decreasing and then increasing, while the production and life functions overall did not change much from 2000 to 2020. ② The county-level carbon emissions in Hunan Province as a whole were not far apart but were concentrated in some areas, and the gap was widening. ③ The spatial-temporal correlation between the P-E-L function and carbon emissions was strong, and the influence degree of different spatial types was different. ④ Considering the general layout of land and space of Hunan Province in 2035, the coefficient of ‘P-E-L’ carbon emissions distribution could be optimised to six combination types in 2035. [Conclusion] Natural endowment and economic development exert a considerable influence on the distribution pattern of ‘P-E-L’ carbon emissions conefficient in counties of Hunan Province. Moreover, regional synergy should be strengthened on the basis of the strategy of main functional zones and refinement control of the county-level P-E-L to achieve the target of carbon neutrality ahead of time.

Abstract:[Objective] The shifts of land use gravity centers and carbon emission change and the influencing factors of land-use carbon emissions in the Chengdu Plain were analyzed to provide theoretical and data support for the low-carbon development of the area. [Methods] Based on multi-source data, the barycenter model and IPCC carbon emission coefficient method were used to elucidate the changes in the land use gravity centers and carbon emissions in the Chengdu Plain from 2006 to 2022. Partial least squares regression analysis and the logarithmic mean divisia index (LMDI) model were used to explore the primary factors influencing cultivated and construction land carbon emissions. A patch-generating land use simulation (PLUS) model was used to simulate future land use patterns and carbon emissions. [Results] ① In terms of land use types, the gravity centers of cultivated land, water area, construction land, and unused land shifted 4.23, 5.46, 8.44 km, and 31.58 km to the northeast, respectively, and forest land and grassland shifted 11.12 km and 3.41 km to the southeast. The gravity centers of major food crops, rice and corn, moved 15.47 km and 7.52 km to the northeast, respectively, whereas that of wheat moved 17.77 km to the southwest. ② From 2006 to 2022, the land use carbon emissions of 33 counties in the Chengdu Plain showed an upward trend, with a total increase of 1.36×10⁷ tons; and the carbon sinks continued to decline, with a total reduction of 5.68×10⁵ tons. ③ Under the natural, carbon sink, and carbon emission reduction scenarios, the carbon emissions from land use reduced by 5.39×10⁵, 3.47×10⁵, 4.53×10⁵ tons, respectively, comparing with those in 2022. [Conclusion] During the study period, a significant loss of cultivated land was observed in the Chengdu Plain; most of it was converted to construction land in the central part of the Chengdu Plain and forest land in the Longmen Mountains, Longquan Mountains, and Leshan City. In the future, the protection of cultivated land should be strengthened necessary. Carbon emissions from land use in 33 counties showed an obvious rising trend; however, the primary influencing factors are different. Therefore, source reduction and sequestration measure should be implemented according to local conditions.