5G base stations are an important area of new infrastructure and a new way to empower industrial optimization and upgrading, economic transformation and investment stimulation. Clarifying the spatial differentiation characteristics of 5G base stations and the factors influencing their spatial distribution has implications for more scientific and rational planning of new infrastructure construction. This paper uses kernel density analysis, spatial autocorrelation analysis and spatial econometric models to comprehensively investigate the spatial patterns and influencing factors of 5G base stations in the Yangtze River Delta region. The results of the article show that: （1) The spatial distribution of 5G base stations at the county scale in the Yangtze River Delta region shows an obvious tendency to concentrate in central areas, forming a “Z” shaped high-value contiguous area in the core of the Yangtze River Delta, with low-value areas primarily distributed in the peripheral areas of the Yangtze River Delta, forming a regional central-peripheral spatial pattern with Shanghai-Nanjing-Hangzhou-Hefei as the core. (2) The high-value areas of 5G base station nucleation density in the Yangtze River Delta region are mainly located in municipalities. There is a clear digital infrastructure divide with non-municipal areas. The low-high heterogeneity area of 5G base stations in the Yangtze River Delta is mainly concentrated on the edge of the municipal area, which belongs to the transition zone from high value to low value area. The high-low heterogeneity area is mainly distributed in the area surrounded by low-low agglomeration areas, and the distribution is relatively isolated. (3) The spatial distribution of 5G base stations in the Yangtze River Delta region is significantly influenced by technical requirements, technical support and spatial factors. Compared to the factors affecting the spatial distribution of traditional information and communication infrastructure, there are some new features of the indicators affecting the spatial distribution of 5G base stations, in addition to factors such as population and level of economic development. For example, the economic subjectivity is clearer, the demand characteristics of specific groups of people are stronger, and the demand orientation of multiple subject types. These are conclusions which, to some extent, are instructive on how to proceed with the spatial allocation of new infrastructure. Finally, several recommendations are summarized on how to conduct 5G base station spatial deployment scientifically and rationally.

Since green development can effectively alleviate ecological and environmental problems, it can promote higher quality integrated development of the Yangtze River Delta Urban Agglomerations. On the basis of sorting theories and mechanisms of green development, this paper develops an indicator evaluation system of green development with six dimensions as scientific and technological innovation, economic growth, resource utilization, environmental governance, environmental quality, and green life, and measures and analyzes the spatial-temporal evolutionary characteristics and future change trends of green development level in Yangtze River Delta Urban Agglomerations from 2006 to 2019 by using Entropy Method, Kernel Density Estimation, and BP Time Series Forecast Model. Research results show that: during the study period: (1) the green development level of the Yangtze River Delta urban agglomerations showed a fluctuating increase in general, and the green development level of some cities declined in 2008-2009 and 2011-2013 due to financial crisis and industrial transfer. （2) green development level between cities had gradually prominent discrepancies, with polarization and a tendency to tripolarization, meanwhile the spatial distribution is uneven. (3) during the “14th Five-Year Plan” period, the green development level will increase further, and it will be improved in the northern and southern regions, but still remain at a low level in the western region. (4) the grade transfer of green development level occurs between adjacent grades, with no “grade skipping” phenomenon and indicating that there is a “bottleneck” of the Yangtze River Delta urban agglomerations. Finally, based on the regional characteristics of the Yangtze River Delta urban agglomerations, this paper proposes corresponding suggestions for green development.

Based on the panel data of 28 cities in the urban agglomeration in the middle reaches of the Yangtze River from 2008 to 2019, this paper has constructed the innovation efficiency evaluation index system, and used the three-stage DEA model to measure urban innovation efficiency and reveal its temporal and spatial characteristics. On this basis, by constructing a variety of spatial weight matrices and using the spatial Dubin model, the main factors and spatial spillover effects of the urban innovation efficiency has been analyzed. The results show that: (1) The urban innovation efficiency of urban agglomeration in the middle reaches of the Yangtze River shows a fluctuating development trend as a whole. The innovation efficiency of each city is obviously different, among which the innovation efficiency of Nanchang, Wuhan, Yichang, Jingzhou and Changsha have relatively high innovation efficiency, cities such as Jingdezhen, Yingtan, Xinyu, Xiaogan, Yueyang and Changde are relatively low. (2) The overall spatial pattern of urban innovation efficiency is characterized by Wuhan as the core, Nanchang and Changsha as important innovation nodes, and gradually decreasing to the surrounding cities, among which the trend of the evolution of high-efficiency areas from west to east is increasingly obvious, higher efficiency areas have shifted from scattered layout to relatively concentrated distribution, medium-efficiency areas are concentrated in patches, while low-efficiency areas are scattered and have a decreasing trend. (3) Urban innovation efficiency has a significant positive spatial spillover effect, which can produce a “trickle-down effect” to the science and technology innovation development of related cities.(4) Regional economic development, education support and transportation level have a significant role in promoting urban innovation efficiency, while opening to the outside world has a negative effect, market structure, financial development and human capital can promote the innovation efficiency of the city, but it has a negative spillover effect on the associated cities; fixed asset investment has a hindering effect on the innovation efficiency of the city, but it can promote the innovation and development of the associated cities.

Reducing CO2 emissions from the industrial sector is one of the key paths to achieving China’s carbon peaking and carbon neutrality goals. In order to enrich the identification of influencing factors of industrial CO2 emissions and the contribution of each influencing factor to the elasticity of decoupling between industrial CO2 emissions and economic development, taking Anhui Province as an example and combining with the C-D production function, this paper quantitatively evaluates the main factors of CO2 emissions in the industry sector from 2006 to 2019 based on the Tapio decoupling model and LMDI model, and analyses the decoupling state between CO2 emission and economic growth, proposing energy efficiency policies accordingly. The results show that: (1) From the time dimension, except for 2013 and 2016-2018, the emission reduction effect was achieved, and the other years were not achieved. (2) Energy intensity suppressed industrial CO2 emissions, with the largest emission reduction in 2011. Technology level and capital investment promote industrial CO2 emissions. Energy structure, economic structure and labor input suppressed industrial CO2 emissions to a certain extent, especially labor input showed a trend of increasing first and then decreasing. (3) There are four decoupling states between industrial CO2 emissions and economic development in Anhui Province: weak decoupling (2008-2012 and 2014-2015), strong decoupling (2013 and 2016-2018), expansion coupling (2006-2007) and expansion negative decoupling (2019). The factors that inhibit decoupling include technology level and capital investment; the factors that promote decoupling include energy intensity and economic structure; the energy structure and labor force gradually change from inhibiting decoupling to promoting decoupling, and the factors of labor input change most significantly. Therefore, the Anhui province should optimize the energy consumption structure and allocation, adheres to the “double control” goal of the realization of energy consumption intensity and total CO2 emissions. At the same time, it must transform the mode of industrial economic development, and develop towards green and intensive industries gradually.

The industry-city integration demonstration zone refers to relying on the existing industrial parks, in accordance with the concept of integrated development of industry and city, accelerating the transformation of industrial parks from a single production-oriented park economy to a comprehensive urban economy. Taking the 46 national-level industry-city integration demonstration zones approved by the National Development and Reform Commission as a sample, the paper compares their differences in population attraction capacity, economic development efficiency, and environmental governance level by region. The paper applied the index evaluation method and the analytic hierarchy method to quantitatively evaluate and evaluate the development of the demonstration area from the two dimensions of development performance and integration performance. The results show that the gradient difference of “east-central-west and northeast” shows the development level of the national industry-city integration demonstration zone, while the performance of the integration of industry and city shows the characteristics of the eastern dominant, relatively balanced and basic coordination in the rest of the region. The paper concludes with suggestions for the development of the integration of industry and city in different regions.

The construction of the Three Gorges Dam altered hydrological regime, and impact on ecosystem and fish resources of the Yangtze River. The study applied the Ranges of Variability Approach (RVA) based on dividing hydrological periods to identify fish sensitive hydrological periods greatly influencing fish resources and assess the impact of key indicators of hydrologic alteration on fish resources in the middle typical reaches of the Yangtze River. The results showed that fish biomass of commercial fishes downstream of the Three Gorges Dam were greatly affected by the changes of discharge during flow rising period (March-June) at Yichang reach. The fry of four major Chinese carps were greatly affected by the changes of discharge during drying period (December-February) at Jianli reach. The fishery fish catch of the Dongting Lake were greatly affected by the changes of discharge during flooding period (July-September) near reaches of the Dongting Lake. The fishery fish catch of the Poyang Lake were greatly affected by the fluctuation of water level during retreating period (October-November) near reaches of the Poyang Lake. During these hydrological periods, the changes of key hydrological indicators, which describe extreme annual flow and duration, the change rate and frequency of flow had the greatest influence on fish resources in the middle typical reaches of the Yangtze River. Compared with traditional RVA without dividing hydrological periods, our study could identify the fish sensitive hydrological period and more indicators of hydrological alteration (IHAs) that greatly affect fish resources, also could quantify their impact on fish resources. The results could provide scientific thesis for fishery resources protection in the Yangtze River and the optimal operation of the Three Gorges Reservoir.

The East Dongting Lake is the largest lake group of Dongting Lake and one of the important wetland nature reserves in China, which has important ecological value. In order to investigate the current situation of fish resources in East Dongting Lake in Hunan Province in the early stage of lifting the fishing ban, an echosounder (EY60,200 KHZ) was used to detect fish resources in East Dongting Lake in May and August, 2021. The results showed that at the daily scale, the density of fish at night in May and August was higher than that at day, and there was a significant difference in the density between day and night in August (F=4.498, P<0.05), but there was no significant difference in the intensity of target between May and August (P>0.05); At the seasonal scale, the average density of fish in May was significantly higher than that in August (P<0.05). There was no significant difference in fish target strength (P>0.05). At the spatial scale, the distribution of fish density was uneven. Fish mainly distributed in northeast lake area and east Lake area in May, while fish mainly distributed in east Lake area and Lujiao area in August. In the vertical distribution, fish mainly distributed in the upper and middle layers of water in May, and in the lower and middle layers of water in August. The total number of fish in August was 7.69×108  and 1.78×109 ind. by using the resource density and volume method, which increased exponentially compared with the historical data. This paper is the first to study the spatial and temporal distribution characteristics of fish in East Dongting Lake in the early stage of fishing ban. The increase of fish resources in East Dongting Lake will provide data basis for the protection and rational utilization of fishery resources in East Dongting Lake after fishing ban.

The cultivated land requisition-compensation balance policy plays an important role in stabilizing the cultivated land area and ensuring food security in China. However, in the process of policy implementation, alienation behaviors such as occupying paddy fields to supplement drylands and destroying ecology are common. How to coordinate the relationship between cultivated land protection and wetlands ecological environment is a hot issue that needs to be solved urgently. By discussing the impact mechanism and characteristics of cultivated land requisition-compensation balance policy on wetlands changes, this study analyzes the temporal and spatial change of wetlands quantity in Hunan Province under the cultivated land protection policy by using the methods of transfer matrix, spatial analysis, and landscape development intensity index, and studies the impact of the policy on wetlands ecological quality. The research results are as follows: (1) the occupation of paddy fields by construction from 2009 to 2018 is one of the main reasons for the reduction of wetlands areas in Hunan Province. Although the paddy field requisition-compensation balance policy effectively controlled the reduction rate of wetlands area in Hunan Province from 2014 to 2018, it also improved the ratio of natural wetlands to paddy fields. (2) From the perspective of space, due to the occupation of constructed wetlands (paddy fields) by urban construction, economically developed urban areas such as Changsha, Xiangtan and Changde are the areas with more reduction of wetlands in Hunan. And the areas around Dongting Lake are the areas with more reduction of natural wetlands. (3) From 2009 to 2018, wetlands in Hunan Province have been increasingly disturbed by human activities, and their ecological quality has shown a continuous downward trend. The study suggests that in the future, implementing a scientifically and systematically cultivated land occupation-compensation balance policy is needed to continue. While strictly controlling the occupation of paddy fields by construction land, not only the supplement of high-quality paddy fields should be strengthened, but also paid attention to the protection of natural wetlands. The research results can provide support for further improving the cultivated land protection policy in the future.

Species diversity investigation and priority protection evaluation are the basis for the protection of rare and endangered plants. In this paper, the analytic hierarchy process (AHP) was used to build the priority protection evaluation index system. We calculated and analyzed the endangered value, genetic value, species value, comprehensive evaluation value, and the priority protection grade, in combination with the distribution of Cypripedium plants in the upper reaches of Minjiang river, to determine the priority protection areas at various levels. The results showed that the first priority protection species are C. micranthum, C. palangshanense and C. sichuanense. The second priority species are C. farreri, C. franchetii, C. ludlowii, C. debile, C. smithii. The third grade priority protection species are C. fasciolatum, C. fargesii, C. plectrochilum, C. shanxiense, and the fourth priority species are C. henryi, C. bardolphianum, C. guttatum, C. flavum, C. tibeticum. The Wolong Nature Reserve, Huanglong Temple Nature Reserve and Jiuzhaigou Forest Park belong to the class I of priority protection areas, with an area of 275 280 hm² (41%). The Gonggangling Nature Reserve and Munigou Scenic Spot are class II of priority protection areas with an area of 172 022 hm² (26%). The Kalonggou Nature Reserve, Dagu Glacier Scenic Spot, Miyaro Nature Reserve, Jiudingshan Nature Reserve and Caopo Nature Reserve are the priority protection areas of class III, with an area of 225 155 hm2 (33%). The results provided scientific supports for special research and conservation of Cypripedium plants in the upper reaches of Minjiang river.

The population dynamic of secondary succession stage of degraded artificial Picea asperata forest of Shatan forest farm in Bailongjiang upstream was studied and its dominant population structure, static life table, survival curve were analyzed based on field investigation and data statistics with quantitative methods and time series models, in order to comprehend its species composition and survival status and predict the trend of population development as a theoretical basis for sustainable management of secondary forest in this forest area in the future. The result showed that there were 13 species in arbor layer of secondary forest community and large quantities of artificial P. asperata forests trees in the community. As dominant species in the community, the sum of important values of Betula albosinensis, Betula utilis and Abies faxoniana accounted for more than 80% of all. Moreover, A. faxoniana as expanding population, owned complete population structure, relatively stable life expectancy and mortality rates and higher survival rate of young individuals. Conversely, Birch forest had lower survival rate of young individuals, fluctuating life expectancy and unstable population structure. Furthermore, the survival curves of the 3 dominant populations were consistent with Deevey-Ⅱ, but some differences existed, and the structures of other small populations were mostly incomplete. In addition, quantitative dynamic analysis showed that the 3 dominant populations were all expanding populations. A. faxoniana had highest population stability, then B. albosinensis, and B. utilis was vulnerable to external disturbance. Finally, this study indicated that the existing community was Birch-A. faxoniana forest community in study area, and every population was still in the stage of mutual adaptation and showed unstable community structure. The population of A. faxoniana regenerate better and emerged further growth trend, but Birch forest went into decline and P. asperata forest plantation would be completely phased out. The community had an obvious tendency to become fir forest community, that was the succession process was P. asperata forest plantation, secondary forest, then A. faxoniana community, so advantages for the growth of fir forest should be provided in the future.

Based on the rainfall data and MODIS/cloud water path product of Danjiangkou Basin from 2001 to 2021, statistical methods are used to analyze the spatial and temporal evolution characteristics and correlation between cloud water and area rainfall. The results show that: (1) In the past 21 years, the area rainfall of Danjiangkou Basin has increased slightly, the spatial distribution is more in the southwest and less in the northeast, and the seasonal characteristics are significant. (2) The average annual liquid water path of Danjiangkou Basin is less than 300 g/m², the seasonal variation is not obvious, and the spatial difference is not significant, which is related to the limitation of MODIS retrieving algorithm; while the ice water path and the cloud water path are 150~500 g/m² and 250~750 g/m², respectively, all peaked in summer. The seasonal characteristics are consistent with area rainfall, due to the influence of topography, the geographical distribution characteristics are obvious. Quantitative analysis shows that there is a good correlation between cloud water path and areal rainfall (the correlation coefficient is 0.73). (3) The “cloud water renewal period” of Danjiangkou Basin is longer in winter, up to 34.5 hours in December, while the cloud water circulation is faster in summer, the renewal period in July is only 2.7 hours.

The zone from Changjiang Estuary Turbidity Maximum to offshore region is the main area of “source-sink transition” for fluvial sediment. It is of great significance to study the changes of regional suspended sediment concentration (SSC) and suspended sediment flux under the background of 70% fluvial sediment reduction at Datong Station. This paper analyzes the measured data based on the spring and neap tidal water and sediment observation data in the flood and dry seasons in 1982 and 2013, and mainly obtains the following insights: (1) Compared with 1982, due to the significant decrease of fluvial sediment, the vertical average SSC and the suspended sediment flux during the spring and neap tides in the dry season and the neap tides in the flood season in 2013 decreased by 40% and 25% respectively; (2) Affected by projects such as estuary waterway improvement and reclamation, the hydrodynamic conditions in local areas have been enhanced, it became an important reason for the increase of 80% and 114% in the vertical average SSC and suspended sediment flux in the North Passage and the South Passage during the spring tides in 2013 flood season; (3) The source-sink transition is manifested in the fact that in the flood season in 2013, the sediment mainly transported into the estuary from the Nanhui nearshore area increased by 101% compared with 1982, and this part of the sediment became an important part of the sediment transport cycle in the North and South Channel. The research results are of great significance for quantitatively evaluating the response of fluvial sediment reduction and local engineering in the estuary area.

In the current period of territorial spatial planning, island cities, as relatively independent natural geographical units, have fragile and unique ecosystems. Therefore, it is necessary to formulate spatial planning based on the refined assessment of ecological security pattern. In this paper, Zhoushan Island is taken as the study area, and the remote sensing ecological index (RSEI) is adopted to evaluate the ecological environment quality. Island geographical characteristics and ecological processes are considered for construction of ecological security pattern. Based on the analysis of factors overlapping and spatial conflict, the spatial optimization scheme and partition control strategy of territorial spatial structure are proposed. The research results show that: (1) The ecological environment quality of Zhoushan island is generally good, but the spatial difference is significant. The high-value coverage ratio of RSEI is 60.94%, showing a three-circle increasing structure from shore to land. (2) The core ecological elements of "source-corridor-buffer zone" stabilize the ecological security of the whole island. Ecological sources accounted for 43.32%, occupying the core hinterland; There are 67 ecological corridors with a total length of 276.5 km, which are concentrated in the patch fragmentation area of the southern ecological source area. (3) Spatial conflicts are concentrated in the central and southern parts of the island, mainly caused by the expansion of new towns and industrial development, the spatial optimization scheme of "one axis-four corridors-five areas-nine capes" and the strategy of ecological restoration zoning of "core conservation area, buffer restoration area and optimization coordination area" are constructed. By contrast between land and sea, this study forms two optimal patterns of island cities, namely "internal source-external corridor-peripheral buffer" and "aggregate with outlines", aiming at provide reference for the ecological security pattern and territorial spatial planning of island cities.

As the highest spatial organization form of urban development, the urban agglomerations will inevitably have a coercive impact on the regional ecological environment in the process of high-speed urbanization. How to balance the ecological environment and urbanization development has become an issue worthy of attention. Based on the cloud platform of Google Earth Engine, the improved night light index and remote sensing ecological index are adopted respectively to characterize the level of urbanization and the quality of ecological environment by making use of the long time series night light image data and Landsat image data from 1995 to 2020. And the variation characteristics of urbanization and ecological environment of urban agglomeration in the middle reaches of the Yangtze River are analyzed. By introducing the coupling and coordinated development model, the coupling coordination degree between urbanization and eco-environmental of urban agglomeration in the middle reaches of the Yangtze River is evaluated and its variation characteristics are analyzed. The research results show that: (1) The urbanization of the urban agglomeration in the middle reaches of the Yangtze River has experienced three stages: low level (1995-2005)-rapid development (2005-2015)-medium level (2020). It has gradually formed a trend of radiation around Wuhan, Changsha and Nanchang. However, there are still some imbalances in regional development. (2) The ecological environment has experienced three stages of stabilization-decline-recovery, but the overall quality is comparatively good and the change stage is basically consistent with urbanization. (3) The urbanization and ecological environment of Wuhan, Changsha and Nanchang have rapidly entered into the state of coordination, reached the medium and high degree of coordination. The surrounding cities which are closely connected with the central city also gradually transition from maladjusted state to moderate coordinated state. At the same time, more than half of the cities have been in the state of dissonance to varying degrees for a long time, but the overall trend is changing towards coordination. By 2020, only a few of these cities are still in the state of mild dissonance, and the rest have reached a state of basic coordination.

Variations in basin land surface are influenced by both climate change and human activities, which largely altered the hydrological connectivity of the catchment, leading to many eco-environmental problems to develop. In this paper, we considered the Poyang Lake catchment as the study area, and used the system for automated geoscience analyses (SAGA) combining the topographic wetness index and network index method to perform connectivity analysis. We analyzed the spatial pattern of hydrological connectivity, and revealed the impact of slope change, land uses, and soil types on hydrological connectivity. Additionally, the relationships between hydrological connectivity and soil erosion and flood disaster were explored for the purpose of application. The results found that the hydrological connectivity of the Poyang Lake catchment is generally high in the northern catchment and relatively low in the southern catchment. In general, the Poyang Lake catchment can be divided into three sub-regions, including the strong hydrological connection area around the lake, the medium connectivity area around the river system, and the weak connectivity area in the upstream mountainous catchment. Spatial analysis further showed that NI values in low-lying areas with low slope is generally high, while aera with large fluctuation area NI values is small. That is, topographic factors have an important impact on hydrological connectivity. In terms of different land uses, the hydrological connectivity of shrub and forest is weak, and that of wetland, water body and cultivated land is high. For different soil types, the hydrological connectivity of yellow soil and yellow brown soil is the worst, and that of alluvial soil, water area and paddy soil is better. This is because the dominant role of the catchment topography, but the soil infiltration capacity, water storage and runoff characteristics of the underlying surface may play a combine role in affecting the spatial difference in the hydrological connectivity. Although this study focuses on hydrological connectivity from a macro perspective, it can provide decision-making basis for watershed soil protection, land use planning, and natural disaster response.

Accurately grasping the evolution trend of the ecological environment and effectively identifying its influencing factors are decisive for ecological environmental protection and the realization of sustainable development. This paper uses remote sensing technology to obtain the ecological factor indicators of the Three Gorges Reservoir from 2000 to 2020, constructs the Remote Sensing Ecological Index (RSEI), uses grid technology to map the administrative area of RSEI, and uses the geographic detector model to measure the impact of economic and social factors on the quality of the ecological environment. The results show that: (1) The overall ecological environment quality of the Three Gorges Reservoir area is showing a positive trend, and the areas with “medium” and “good” ecological environment quality levels account for an average of 72%. (2) The ecological environment of the Hubei section of the Three Gorges Reservoir area is better than that of the Chongqing section. The ecological environment of Xingshan County in Hubei is the best, with an average RSEI index of 0.474. The areas with poor ecological environment are concentrated in the core urban area of Chongqing. (3)Population density, urbanization, and the three major industries have a significant impact on the ecological environment, and per capita GDP can be linked with other factors to have a strong influence. Studies have shown that to improve the ecological environment of the Three Gorges Reservoir area, it is necessary to further improve the economic level, pay attention to the transformation of the secondary industry, and focus on controlling the population size and urbanization development.

To meet the needs of food security, ecological security and urban development, the Chinese government proposed the system of Requisition-Compensation Balance to swap the spatial position between farmland, forest land and construction land. However, this system also makes a large amount of farmland abandoned, which has violated China's policy of "Hiding Grain in the Land". The methods of binary logic regression model and grain capacity accounting model were used to analyze the phenomenon, causes, and grain productivity effects of farmland abandoned in Wannian County, a mountainous agricultural county. The study found that: (1) From 2010 to 2020, the supplementary farmland in Wannian County has been uphill and fragmented, and the abandonment rate has reached about 14.77%. (2) The farmland is more likely to be abandoned when its altitude>130 m and patch area<0.2 hm², or permanent population density of the located village <400 people/km2 and patch area<0.2 hm², or patch area<0.2 hm² and traffic distance with adjacent farmland＞40 m, or altitude>110m and traffic distance with adjacent farmland＞70 m. (3) 3 183.39 hm2 of forest land can be reclaimed in county areas, of which forest land, other forest land, and sparse forest land account for 88.25%, 9.74% and 2.01% respectively. (4) The replacement of farmland and sparse forest space can make up for the loss of 297.48 t production capacity caused by the abandonment. The study has shown that the abandonment of farmland is the result of spatial mismatch caused by the coupling relationship between land use conditions-state-functions.Therefore, we put forward joint strategies of requisition-compensation balance among farmland, forest land, and construction land in mountainous areas, so that the farmland uphill can be swapped to the place suitable for cultivating by humans.

Exploring the influencing factors and marginal utility of rural development in different regions is of great significance for the in-depth implementation of the rural revitalization strategy. Taking 513 villages in different regions of Chongqing as examples, the study, based on the multiple linear regression and boosted regression tree (BRT) models, analyzes the influencing factors and marginal utility of rural development in six aspects: resource endowment, geographic location, human capital, industrial base, facility construction and governance level. The results are as follows: (1) Industrial base plays an important role in promoting rural development in different regions. (2) The degree of industrial organization, the resident population, villagers' participation and the vitality of industrial development are significantly and positively correlated with the rural development in counties with better economic development, with increased marginal utility; the degree of industrial organization, the scale of land transfer, resident cadres and arable land resources are significantly and positively correlated with the rural development in counties with lagging economic development, with the increased marginal utility of factors other than resident cadres. (3) Due to the influence of labor outflow, labor force is negatively correlated with rural development in counties with better economic development, with reduced marginal utility. And resident cadres have a significant positive effect on enhancing the effectiveness of rural governance in counties with lagging economic development. The study suggests that rural development in counties with better economic development should further integrate the resource elements of "people, land, and industry" and give full play to farmers' enthusiasm in rural development, while counties with lagging economic development should focus on breaking through bottlenecks in rural development, improving industrial development capacity, and relying on resident cadres to enhance the effectiveness of rural governance.

Low-carbon agriculture is an important practice of green development concept in agriculture, and technological progress is an important factor to promote agricultural carbon emission reduction. Based on the panel data of China's main grain producing areas from 2008 to 2019, this paper firstly calculates the rebound effect of agricultural carbon emissions caused by technological progress, further discusses its formation mechanism and characteristics. The results show that: (1) There are obvious differences in the agricultural carbon emissions among various regions, and displays an obvious ‘up-down’ phase-change characteristic. (2) On the one hand, agricultural technological progress can reduce the intensity of agricultural carbon emissions. On the other hand, agricultural technological progress can promote agricultural economic growth, increase agricultural resources investment, increase agricultural carbon emissions, resulting in a rebound effect. (3)Agricultural carbon emissions in main grain producing areas generally have rebound effect, and some provinces have tempering effect. There are differences among various regions and various years. Finally, this paper puts forward corresponding countermeasures and suggestions to reduce the rebound effect of agricultural carbon emission in main grain producing areas.