Based on 30 m resolution remote-sensing classified land use/land cover data from GLC_FCS30 and GlobeLand30 in 2020, and combined with spatiotemporal data, such as topography and microclimate, transportation, alpine timberline, ecogeographical zoning, as well as changes in Miami climatic potential productivity, this study has obtained the spatial distribution and quality of China's potential forestation land with a resolution of 30 m by selecting the grassland and cultivated land with a slope greater than 25° as the potential land source and applying Liebig's "Law of the Minimum". The results show that China lacks potential forestation land of high quality; as the quality level decreases, its area increases. Among potential forestation land, the area of prioritized potential forestation land is 0.66 million km², of which the total multiyear average Miami climatic potential productivity is 630 million tons. If all the prioritized potential forestation land is developed for forest plantations, the national forest coverage rate would increase by 6.94%, and the corresponding climatic potential productivity would increase by 25.00%. The area of prioritized potential forestation land in North China is the highest and two-thirds of this area is observed in Inner Mongolia, while the climatic potential productivity in Southwest China is the highest, 1.59 times that in North China. Among the prioritized potential forestation land, the areas for afforestation and reforestation accounted for 59.56% and 40.44%, respectively, but the climatic potential productivity accounted for 47.94% and 52.06%, respectively. Therefore, in future forestry, we must not only actively deploy afforestation land but also strengthen forest restoration in areas with better climatic conditions. The spatial distribution of potential forestation land with a resolution of 30 m obtained in this study can provide an important reference for the nationwide forest planting plan for carbon sequestration.

Chinese terrestrial ecosystems play an important role in the global carbon cycle. Net primary productivity (NPP) of vegetation is an important carbon cycle component. However, the report was seldom found until present on the trends and stability of NPP and its climate impact for Chinese terrestrial vegetations. In this study, through an ecosystem process model CEVSA-RS developed previously, the NPP was simulated for Chinese vegetation under climate scenarios of RCP4.5 and RCP8.5 for the period from 2006 to 2099. The interannual trends and turning points were analyzed by segmented linear regression. The moving window method was applied to quantify the changes of NPP stability and the effects of temperature and precipitation. The results showed that: (1) the total NPP of vegetation in China will be respectively 4.41 Pg C a^-1 and 4.40 Pg C a^-1 under two climate scenarios. The temperate and tropical-subtropical monsoon zones together contribute 72.8% (RCP4.5) and 73.4% (RCP8.5) in the national total NPP. (2) NPP will have an increasing and then a decreasing trend with the turning points respectively in 2062 and 2055 under the two climate scenarios. Specifically, NPP will increase significantly (p<0.01) by the rates of 5.3 g C m^-2 10a^-1 and 6.5 g Cm^-2 10a^-1 before the turning points, and then significantly accelerate a decrease by the rate of 4.28 and 2.57 times higher than those before turning points, respectively, for the two scenarios. (3) The NPP stability will significantly (p<0.01) decrease by the rates of -2.9% and -4.3% every 11 years under the two scenarios respectively. The NPP stability after turning year will decrease to 68.33% (RCP4.5) and 54.57% (RCP8.5) of the previous turning year, respectively. (4) In the future, the temperature will be significant warmer by the rates of 0.2 °C and 0.4 °C per decade under both of the scenarios, while precipitation will change insignificantly under RCP4.5 scenario but will be wetter by the rate of 2.9 mm per decade under the RCP8.5 scenario. Therefore, the drought indices, calculated from temperature and precipitation, will decrease significantly (p< 0.01) by the rates of -0.5 and -1.2 per decade under the two scenarios and the future climate will be warmer and drier. Responding to the future climate change, NPP will have a downward trend after 2055 over Chinese terrestrial ecosystems due to drought under the RCP8.5 scenario. This study reveals that in the future more instable warm and dry climate will cause a declining and instable NPP over the terrestrial ecosystems, which will probably result in some ecological and environmental problems, such as decreasing ecosystem services. Further, this study indicates that the policies and measures, such as carbon neutrality by 2050 implemented in China, are essential to mitigate and adapt climate change.

Southwest China is an important carbon sink region in China. Monitoring vegetation dynamics and exploring the impacts of climate change and human activities on vegetation are essential for gaining insight into carbon cycle mechanisms and promoting sustainable economic development. In this paper, downscaled NDVI data were obtained by fusing the GIMMS NDVI and SPOT NDVI. Then, the data were combined with multitemporal land use and meteorological data to explore the relative contributions of human activities and climate change to vegetation dynamics in Southwest China from 1982 to 2019 by using trend analysis, partial correlation analysis and residual trend analysis. The results are obtained as follows: (1) From 1982 to 2019, the NDVI showed an overall increasing trend in the study area, with an average annual rate of 0.0020 a^-1; the NDVI showed a decreasing trend before the Grain to Green Program (GTGP) was implemented, but it turned to an increasing trend after the implementation of the GTGP. (2) Temperature and precipitation increased NDVI as a whole, but there was apparent spatial heterogeneity. Except in the central cities, temperature mainly promoted the NDVI. However, precipitation inhibited the NDVI in the western part of the study area and promoted the NDVI in the eastern part. (3) As the areas affected by climate change and human activities became separated, the contribution of climate change to vegetation recovery increased from 30.47% to 60.28%. In comparison, the contribution of human activities to vegetation recovery decreased from 69.53% to 39.72%. The results suggest that the impact of human activity on vegetation may decline further in the sparsely populated western part of the southwest region.

Compared to traditional optical remote sensing indicators, the microwave remote sensing indicator vegetation optical depth (VOD) is less sensitive to clouds and atmosphere, and also less susceptible to saturation. The VOD is capable of monitoring changes in the total water content and biomass of vegetation. In this study, we analyzed the spatio-temporal dynamics of VOD in different regions of China and different vegetation types from 2000 to 2018 based on multiple frequencies of VOD datasets (VODCA C-VOD, X-VOD, Ku-VOD, and AMSRU X-VOD) using trend analysis and residual analysis. Then, the relative contributions of climate change and human activities at national and regional scales were quantitatively assessed. Results showed the following. (1) All of the VOD increased significantly over this period. AMSRU X-VOD had the fastest growth rate (0.062/10a), especially in eastern China. VODCA C-VOD increased at the lowest rate (0.013/10a), which showed the highest increasing rate in southwestern China. The fastest increasing trend of VOD was observed in grasslands, followed by needleleaf forests and scrubs. (2) The rising precipitation and radiation promoted the increase of VOD in northern and northwestern China. The temperature was closely related to the VOD changes in southern China and coastal areas. The contribution of radiation on Ku-VOD and X-VOD representing vegetation canopy was higher than that of precipitation and temperature. (3) According to different datasets, human activities were the primary factor for the increase in VOD. The contribution of human activities to VODCA C-VOD, Ku-VOD, X-VOD, and AMSRU X-VOD was 171%, 48%, 43%, and 30%, respectively, especially in the Loess Plateau, southwestern China, and Northeast China Plain. The outcomes of this study shed new light on the efficiency evaluation of ecological projects, which will provide guidance for future ecosystems management and environment protection in China.

Water and soil resources are indispensable for the development of agricultural production. However, the uneven spatial and temporal distribution of water resources and the mismatch of arable land distribution have emerged as critical issues affecting the sustainable development of agriculture in China. Based on the existing arable land, this study focuses on the synergy between grain production security and sustainable water resource utilization, with the objective of securing grain production while reducing water consumption and regional water stress, and uses the CPLEX optimization model to optimize the pattern of major crops (soybean, rice, maize, and wheat) in China based on data such as pixel-scale crop yield, water consumption, and regional water stress. Furthermore, this study analyzes the water resource effects of crops in terms of their water use efficiency and water resource stress. The results indicate that: (1) Under the premise of guaranteeing the crop yield remains unchanged, the pattern optimization of crops by province can reduce the total water consumption by up to 3.63×10¹⁰ m³ (a decrease of 9.60%), the average baseline water stress falls from 1.42 to 0.90, and the sown area can be reduced by 3.08×10⁶ hm² (a decrease of 3.29%). (2) Distinct crops have a different optimization direction. Soybeans should be reduced in the northern part of the Northeast Region and the southern part of the Huang-Huai-Hai Region, the pattern adjustment of rice should be made mainly in the Middle and Lower Yangtze River Region and the central part of the South China Region, the maize should be moved to the northeast as a whole and adjusted mainly within the Northeast Region and the Huang-Huai-Hai Region, while the wheat should be adjusted mainly in the Huang-Huai-Hai Region and the northern part of the Middle and Lower Yangtze River Region. (3) Under crop collaborative optimization, the irrigation water consumption of wheat can be decreased by 3.08%, while the reductions of the remaining three crops range from 20% to 30%, with the largest reduction for rice (8.52×10⁹ m³). (4) The impact of crop pattern optimization on regional water resources varies among provinces. More specifically, crop pattern optimization in Heilongjiang, Xinjiang, Inner Mongolia and Anhui contributed the most to the reduction in irrigation water consumption, while Sichuan, Gansu and Shandong mainly manifested a shift of crops to areas with less water resource stress, but with a slight increase in total irrigation water consumption. This study can provide decision-making suggestions and technical support for the sustainable use of water and land resources in agricultural production.

Urban green space recreational service is one of the types of urban ecosystem services that are closely related to urban residents. Identifying the key areas of imbalance between supply and demand of urban green space recreational service and prioritizing the planning intervention will play an important role in accurately improving the supply efficiency of urban green space recreational service and meeting the needs of urban residents for high-quality recreational functions. This paper takes Xiamen Island as the research object, and conducts quantitative analysis using 2019 remote sensing data, point of interest data, statistical data and other multi-source data. And, the spatial analysis tools such as InVEST model, ArcGIS platform and GeoDA are used to build the evaluation index system and research framework of urban green space recreation service supply and demand. On this basis, the supply and demand level and spatial clustering characteristics are evaluated, and the key areas of supply and demand imbalance and the priority of planning intervention are identified. The main results are as follows: (1) The habitat quality and vegetation growth status of Xiamen Island showed the spatial distribution characteristics of "superior in the south and inferior in the north"; there are significant spatial agglomeration characteristics in the supply capacity of urban green space recreational service, and high-high hotspots are concentrated in the southern and western parts of the study area. (2) Both the density of permanent population and the density of POI cores showed the characteristics of spatial agglomeration of "overall homogeneity and concentration of areas"; the per capita enjoyment rate of green space resources among special groups varies greatly; the demand level of urban green space recreational service is opposite to the spatial agglomeration characteristics of supply capacity, and high-high hotspots are scattered in the southwest and central parts. (3) A total of 387 key units of the "low supply-high demand" imbalance were identified, mainly distributed in residential areas in the central and northern parts of Xiamen Island, which faced the severe challenge of insufficient supply of urban green space recreational service and needed to be repaired and optimized. (4) Five planning intervention priorities are divided, and 44 units are in the IV-V priority area, which requires priority intervention to accurately alleviate the contradiction between supply and demand of urban green space recreational service.