It is of great significance for regional ecological construction to grasp the dynamic change characteristics of ecosystem service value (ESV) and clarify the evolution trend of its leading factors. Based on the remote sensing interpretation data of 2005, 2010, 2015 and 2019, the characteristics of ESV dynamic changes in Hubei Province were analyzed using the equivalent factor method and spatial statistical tools. Furthermore, the random forest model was used to clarify the dominant factors of ESV, and the spatio-temporal weighted regression model was further used to explore the dominant factors. The results show that (1) the amount of ESV in Hubei Province from 2005 to 2019 decreased by 124.31×10⁸ yuan, but the ESV’s decreasing rate at 2005-2010 decreased from 1.14% to 0.57% during 2015-2019. Over the years, ESVs presented a distribution feature of “higher in the surrounding and lower in the middle”. During the study period, ESV in 83.4% regions fluctuated slightly and presented at a stable spatial distribution. (2) The results of random forest sequencing showed that social and economic factors were more important to ESV, followed by natural factors. The most important factors were human activity (60.16%), net primary productivity (50.66%), annual rainfall (46.85%), gross regional product density (34.00%), population density (29.53%) and construction land proportion (29.36%), respectively, and the topographic and temperature ranked behind of them. The results of the importance of ESV leading factors changes showed that factors increased in varying degrees, except the human activities and precipitation. (3) The strength and fluctuation trends of the dominant factors for ESV in different regions varied. Human activities had the strongest driving effect on ESV, showing a global negative correlation, which was most obvious in western Hubei. The positive impact area of net primary productivity was mainly located in the east of Enshi County, the west of Yichang City and the west of Shiyan City. The negative impact of annual rainfall was gradually stabilized in the Jianghan Plain. The fluctuation trends of population density and GDP density in the Three Gorges and Danjiangkou reservoir areas diverged since 2010. The fluctuation trend of the proportion of construction land was positive at west and negative at east. The research results can provide a theoretical basis for the formulation of ecological protection policies and sustainable development in Hubei Province.

Grassland is the largest terrestrial ecosystem, which possesses extremely important production and ecological functions. Long-term overutilization and climate change, however, have contributed to degradations of grassland ecosystems worldwide. The natural restoration of degraded grasslands takes long time, and manipulating practices could be indispensable to accelerate the restoration. Although grassland ecological restorations have been studied for several decades in China, the phenomenon of degradation-restoration-re-degradation-re-restoration is common, and grassland degradation has not been comprehensively improved due to the ecological functions have not been paid enough attention. Lately, ecological priority and green development are emphasized, and more attention has been paid to grassland protection and ecological restoration. Restoration of degraded grassland ecosystems is a major problem and daunting task to be solved urgently in China. To provide scientific references for the ecological restoration of degraded grasslands, we reviewed the researches of grassland ecological restoration, as well as the main practical and policy measures. Restoration effects, limiting factors and existing shortcomings of different practical measures (no-tillage sowing, rational grazing, artificial pasture establishment, fence enclosure, tillage and fertilization) were also assessed. On these bases, research directions and suggestions for the grassland ecological restoration in the future were put forth: (1) To establish a modern grass husbandry system and management pattern to fundamentally solve the contradiction between grass and livestock is the prime way to tackle the grassland degradation and ecological restoration; (2) To improve the grassland degradation classification and grading system to provide theoretical bases for ecological restoration; (3) To strengthen the development and utilization of native grass germplasms and soil microorganisms to provide material support for ecological restoration; (4) To break through the theoretical and technical bottlenecks to restore the grasslands full of poisonous weeds; (5) To build a region-classification-grade theoretical and technical system and evaluation system of ecological restoration. Grassland ecological restoration is a complicated, transdisciplinary and systematic engineering, and the key is to strengthen multi-field cooperation.

Forest soil microorganisms determine the energy flow and material cycle of forest ecosystems, and their community structure and influencing factors are significant to maintain ecosystem stability and respond to global climate change. Phospholipid fatty acids (PLFAs) can be used as biomarkers to directly reflect the biomass and community structure of different microbial communities in soil because they only exist in living microorganisms. This study focuses on soil microorganisms and uses the PLFA method to analyze the community structure, biomass, and physicochemical properties of microorganisms in natural forest soils from all six climate types in China. The main factors affecting the microbial community structure were analyzed using correlation analysis and redundancy analysis methods. The analysis results indicate that there are significant differences in soil density, soil pH, soil litter carbon content, soil organic carbon content, soil total nitrogen content, soil carbon nitrogen ratio, and soil total phosphorus content among the six climate types. There are significant differences in fungal community biomass among the six climate types, with a trend of first increasing and then decreasing as the climate types change from cold zone to temperate zone to tropical zone. The ratio of fungi to bacteria in warm temperate soil is the highest (0.7), significantly higher than that in subtropical and tropical soils (0.4-0.5). The ratio of Gram positive to negative bacteria in tropical and alpine soils is significantly higher than that in other climate types (1.3-1.5), with the lowest in subtropical soils (0.7). The climate (annual average temperature, annual precipitation) and soil physicochemical properties (soil pH, soil density, soil total nitrogen content and soil organic carbon content) are significantly correlated with the soil microbial biomass and community structure represented by PLFAs content (P<0.01). This study summarizes that there is no significant difference in the overall microbial biomass represented by total PLFAs among six climate types, but there are significant differences in soil physicochemical properties and microbial community structure. The main influencing factors of forest soil microbial community structure are annual mean temperature, annual mean precipitation and soil pH value. This study reveals the characteristics of forest soil microbial communities in China as a whole, and providing a basis for us to reveal the response of soil microbial communities to climate change in space.

Rice is an important part of the food system in China and the world. It is of great significance to study the life cycle carbon footprint of rice food system from the perspective of food system for low-carbon transformation and green development. Based on statistics from 22 major rice-producing provinces in China in 2018, the cradle-to-market carbon footprint of Rice food systems in China, including its structural composition, regional differences and rice type differences was calculated and analyzed by using the life cycle assessment (LCA) method and the CF-Rice rice carbon footprint calculation tool developed by the International Rice Research Institute (IRRI). The results showed that 1) when comparing carbon footprint per unit production (CO₂ eq), the carbon footprint was in the order of late indica rice (2.31 kg?kg^-1), middle indica rice (1.32 kg?kg^-1), japonica rice (1.13 kg?kg^-1) and early indica rice (1.08 kg?kg^-1). When comparing carbon footprint per unit area (CO₂ eq), the carbon footprint was in the order of late indica rice (9.15×10³ kg?hm^-2), middle indica rice (6.34×10³ kg?hm^-2), japonica rice (5.56×10³ kg?hm^-2) and early indica rice (4.16×10³ kg?hm^-2); 2) Methane (CH₄) in paddy field was the most important component of the carbon footprint of rice food system, accounting for 36.2%-71.5%, followed by fertilization (8.69%-20.0%), harvest (8.41%-18.5%) and prenatal (4.97%-12.1%). Mechanical operations, storage, processing, packaging and transportation, although only accounting for less than 10%, were also significant sources of emissions; 3) early indica rice, middle indica rice and late indica rice showed no obvious spatial distribution pattern, while the main producing areas of japonica rice had a large spatial span and showed an increasing trend of carbon footprint from north to south, specifically as follows: except for Shandong, the carbon footprint of japonica rice in Northeast (Heilongjiang, Jilin, Liaoning) and North China (Inner Mongolia, Hebei) was lower than that in East (Anhui, Jiangsu, Zhejiang), central (Henan, Hubei) and southwestern China (Yunnan); 4) from the perspective of the composition of greenhouse gases, the contribution rate of CH₄ to the carbon footprint of rice food system was the highest, reaching 20.1%-76.4%, followed by that of CO₂ (21.1%-72.3%), and that of N₂O (1.76%-10.7%) was the lowest. The regional and type differences of rice food system carbon footprint were mainly related to climatic conditions, planting management measures and emission factors. Hence, in order to reduce the carbon emissions of rice food system, it is necessary to take overall consideration to reduce the CH₄ emission of rice field, improve water and fertilizer management, reduce energy consumption, and decrease food loss and waste.

In recent years, as a new type of pollutant, microplastic pollution in the water environment has received more and more attention and has become an emerging global environmental problem. In order to understand the pollution characteristics of microplastics in common wild fish in the Pearl River Delta, we selected eight kinds of wild freshwater fish as research objects and analyzed the abundance, particle size, shape, color, and composition of microplastics in their gills and intestines. A total of 60 microplastics were detected in all of the fish, with an average intake of 1.6 microplastics per fish. The average abundance of gills was (0.638±1.276) items∙g^-1, and the average abundance of gut was (0.256±0.326) items∙g^-1, and the average abundance in the gills was greater than that of guts. The correlation analysis between the abundance of microplastics in fish and fish body length and body weight showed that the abundance of microplastics in fish was weakly related to body length or body weight of fish. The microplastic particles detected in this experiment were mostly greater than 100 μm in size, mainly in fragments, and mostly black or gray in color. The types of polymers detected were mainly polyethylene and polypropylene. Most of the microplastics ingested by pelagic fish were in a granular form, and its source may be plastic microbeads added to personal care and cosmetic products, which were discharged into the environment through domestic sewage and then ingested. Most of the microplastics ingested by bottom fish were in the form of fragments, and the source might be solid waste, which sank to the bottom after weathering and photolysis and was then ingested by bottom fish. Misgurnus anguillicaudatus had the highest average microplastic intake, and the fish with the highest microplastic content in their gills and guts were all from the Zuotan sampling site. These research results may help us to understand the status of microplastic pollution in wild freshwater fish populations in the Pearl River Delta and may provide reference for water ecological risk assessment.

With climate warming and high input of nutrients such as nitrogen and phosphorus, CyanoHABs occur frequently in many water bodies around the world, and even rebound in some areas where water quality has been restored. Some cyanobacteria, such as Microcystis aeruginosa and Nostoc, produce microcystins (MCs), which are harmful to human body and water ecological health. In this study, the Web of Science database was used to investigate the reported concentrations of MCs in 324 lakes and reservoirs (1291 data in total) and 15 rivers (96 data in total) in different regions of the world, and water quality index such as water temperature, pH, nitrate, ammonium and the ratio of nitrogen to phosphorus (N/P) were investigated. The results of the study showed that 40.5% of the surveyed water bodies had concentrations of MCs lower than the World Health Organization standard (1 μg·L^-1). The results of correlation analysis showed that there was significant correlations between the mass concentration of MCs in the water body and water environmental factors such as nitrate, ammonium and N/P. Based on the EPA Aquatic Toxicity Database, the risk quotient was used to evaluate the aquatic ecological risk of MC-LR. The study showed that 17.5% of the surveyed water bodies had low risks (0.1<RQ≤1), 10.2% of the water bodies had medium risks (1<RQ≤10), and 1.5% of the water bodies had high risks (RQ>10). In terms of the toxic mechanism of MCs, it is necessary to strengthen the research on the mechanism of MCs on existing diseases (such as inflammation and glycogen dynamic balance disorder) and the effect of MCs on mitochondria, and further study on the effect mechanism of MCs on PP1/2A subunit protein.

Rice production is the main source of carbon emissions. Liaoning Province is a major production area of high-quality rice in China. Exploring the potential of carbon sequestration and emission reduction in rice fields is very important for achieving carbon peak and carbon neutralization. Following the basic framework and requirements of IPCC, we estimated the potential of carbon sequestration and emission reduction of rice fields in Liaoning Province. The results showed that the methane emission (CO₂-eqv) from rice fields in Liaoning Province was 2.13-3.39 Tg·a^-1, and the direct or indirect N₂O emission (CO₂-eqv) was 0.37-0.40 Tg·a^-1 or 0.08-0.09 Tg·a^-1, respectively. The total carbon emission (CO₂-eqv) of conventional fertilization was 2.61 Tg·a^-1. Optimized fertilization could reduce carbon emission (CO₂-eqv) by 0.03 Tg·a^-1. Organic fertilization and straw returning increased carbon emission (CO₂-eqv) by 0.42 Tg·a^-1 and 1.36 Tg·a^-1, respectively. The carbon emission intensity per unit area and per unit yield of rice field were the highest in straw returning, which were 49.96%-52.68% and 50.30%-52.46% higher than those of conventional fertilization. The carbon emission (CO₂) intensity per unit area of rice field in Liaohe Delta was the highest, which was 5.17-8.08 t·hm^-2·a^-1; the carbon emission (CO₂) intensity of unit yield in southeast area of Liaoning Province was the highest, which was 0.66-1.01 t·t^-1·a^-1. Liaohe Delta rice area had the largest carbon emission (CO₂-eqv) reduction potential, which was 5.50-14.20 million tons per annum. Among nutrients, the carbon emission (CO₂-eqv) reduction from nitrogen fertilizer was the largest, which was 0.18-12.00 million tons of per annum; among fertilization methods, organic-inorganic combined fertilization showed the greatest reduction, which was 3.78-14.2 million tons of per annum. The amounts of carbon sequestration (CO₂-eqv) in soil with organic-inorganic combined fertilization and straw returning were 0.10-0.28 Tg·a^-1 and 0.22-0.65 Tg·a^-1, respectively, and the offset ratios of carbon sequestration to soil by increased carbon emission were 56.68%-82.52% and 89.34%-99.03%, respectively. Therefore, organic-inorganic combined fertilization is the best nutrient management measure for carbon emission reduction in rice production in Liaoning Province.

In recent years, ozone pollution in the Pearl River Delta is getting worse. One of the key reasons is the nonlinear relationship between ozone and its precursor concentration; unbalanced precursor reduction may lead to an increase in ozone concentration. Therefore, research on the relationship between ozone and its precursors, as well as the sources of VOCs is of great significance for ozone pollution control. As a representative city of the Pearl River Delta city group, ozone pollution in Zhongshan is extremely serious. In this study, we launched a monitoring campaign in Zhongshan in September of 2020 and 2021, when ozone pollution is relatively severe. Five monitoring sites were selected to represent the air quality of Zhongshan, and both online and offline monitoring methods were used. The results showed that the average TVOC concentration on the Zimaling site in 2021 was 127.5 μg·m^-3, higher than that on the other sites, and increased by 5.2 μg·m^-3 since 2020, mainly due to the large increase of alkane quality concentration from 27.3 μg·m^-3 to 44.6 μg·m^-3；the quality concentration fluctuations of TVOC in September 2020 and 2021 were both significant and irregular, with overall high quality concentration levels in the middle and late stages. Ozone sensitivity analysis showed that ozone formation in Zhongshan City was VOC-limited in September 2020, while it was controlled by a transition regime in September 2021. According to the precursor reduction simulation, emission cut of NO_x and VOCs following a ratio of 1:3 or 1:2 would be a more conducive measure for ozone control. Analysis of ozone formation potential (OFP) at online and offline monitoring stations during the observation period showed that isoprene, m/p-xylene, toluene, o-xylene, 1, 2, 4-trimethylbenzene, and ethylene were the dominant species for ozone formation in Zhongshan City. Source apportionment results showed that vehicle exhaust and oil volatile were the largest sources of VOCs in Zhongshan City in both 2020 and 2021, accounting for 37.4% and 32.4%, respectively, while solvent use source was the largest source of OFP, accounting for 23.6% and 22.2% in 2020 and 2021, respectively. In summary, in order to effectively alleviate the ozone pollution in Zhongshan City, it is recommended to focus on the control of vehicle exhaust, oil volatile sources and solvent use sources.

Owing to the interactions between environmental factors, different conclusions can be drawn about the relationships among soil microbial biomass carbon, nitrogen, and their influencing factors. Thus, it is important to increase research in different ecosystems. To explore the dynamics of soil microbial biomass during the growing season in the Qinghai alpine grassland and the relative contribution of water and heat factors to spatial changes in soil microbial biomass, we conducted studies on the plots set up by the Sanjiangyuan Grassland Ecosystem National Observation and Research Station. The results showed that: (1) The alpine steppes located in the central and western regions of Qinghai Province, especially the Hoh Xil region, had the lowest microbial biomass, while there was relatively high microbial biomass in alpine meadow, alpine meadow steppe, and warm steppe. (2) The seasonal dynamics of soil microbial biomass carbon and nitrogen varied in different regions, and the central western and eastern regions of Qinghai Province exhibited significantly different trends. (3) Using an enhanced regression tree model to quantitatively evaluate the relative contributions of water (soil water content, relative humidity of air, precipitation, and evapotranspiration) and heat (soil temperature, air temperature, and net radiation) factors to microbial biomass changes, it was found that, compared with other water and heat factors, the soil water content (P=0.000) and soil temperature (P=0.000) had the greatest impact on microbial biomass carbon and nitrogen, and both were positively correlated. On the vertical gradient of the soil, the influence of the water factor (63.58%-76.62%) on the change of microbial biomass was greater than that of the heat factor (23.38%-36.42%), but its contribution decreased with depth in the soil layer. Over the whole region, the heat factor (52.11%-81.84%) contributed most to the variation in microbial biomass in the eastern and central regions, while the water factor (66.33%-95.19%) controlled the variation in microbial biomass in the western regions. We conclude that the soil microbial biomass of alpine meadow, alpine meadow steppe, and temperate steppe was significantly higher than that of alpine steppe in Qinghai. The soil water content and soil temperature were the main factors controlling variations in soil microbial biomass. The impact of the factors on the variation of soil microbial biomass across the region showed a transition from the heat factor in the east to the water factor in the west. This study provides a reference for exploring the soil carbon nitrogen cycle and its influencing factors in Qinghai alpine grassland in the context of climate change.

The freeze-thaw cycle (FTC) is an important factor that affects the physicochemical and biological properties of alpine grassland soils. The deposition and degradation of grazing livestock dung during freeze-thaw period may also be affected by the complex and significant effects of FTCs. However, the effects and mechanisms of FTCs on dung degradation and nutrient changes in alpine grassland remain unclear. In this study, a 30-day indoor freeze-thaw simulation experiment was conducted by using yak and Tibetan sheep dung collected from the seasonal freeze-thaw alpine grassland in the northern Tibetan plateau. Dung samples were collected to analyze the physicochemical properties and nutrient concentration after 0, 5, 15, and 30 days of FTCs, respectively, so as to investigate the detailed influences of repeated FTCs on dung degradation and major nutrient dynamics. The results showed that 1) the moisture content and dry matter content of yak dung significantly decreased during the first 15 days of FTCs (P<0.05), and the moisture content of sheep dung decreased by 82.6% in the first 5 days of FTCs. This decrease could be attributed to the repeated FTCs of fresh dung that easily damage the physical structure of dung pats at the initial stage and therefore accelerate the loss of moisture content and dry matter content. 2) The concentration of ammonium nitrogen (NH₄⁺-N) of yak dung reached its maximum after 5 days FTCs (415 mg·kg⁻¹), while the nitrate nitrogen (NO₃⁻-N) concentration of yak and sheep dung significantly decreased across the first 15 days FTCs (P<0.05). The increased organic nitrogen mineralization and enhanced denitrification rate at the early stage of FTCs may be the primary reasons for the brief increase in NH₄⁺-N concentration and sustained decrease in NO₃⁻-N concentration. 3) The concentration of AP in yak dung significantly decreased by 21.2% (P<0.05) from 15 to 30 days of FTCs, while the concentration of AP in Tibetan sheep dung fluctuated throughout the entire experimental period, indicating that yak dung pat AP was variously influenced by later-stage FTCs, whereas particulate sheep dung AP was subject to more complex and variable influences from FTCs across the whole experiment. In summary, repeated FTCs tend to induce changes in the block structure, physicochemical properties, and microbial characteristics of yak and sheep dung to various degrees, thereby resulted in significant variation in the nitrogen and phosphorus migration, transformation, and active nitrogen and phosphorus nutrient concentrations. The conclusions of this study can provide theoretical references for optimizing the management of livestock dung in grassland during the seasonal freeze-thaw period and promoting the healthy development of grassland ecosystems.

Per- and polyfluoroalkyl substances (PFASs) are a diverse group of emerging persistent organic pollutants (POPs) known for their versatile applications, complicated properties, and associated ecological and health risks through environmental pollution. While previous published reviews have summarized the sources and distribution of PFASs in soil and water ecosystems, this paper aims to fill the crucial gap by a systematic overview of their sources, spatial and temporal distribution, and human health risk assessment in the atmospheric environment. Sources of PFASs in atmosphere include the industrial production and application of fluoropolymers, product consumption, waste treatment, volatilization and sublimation from soil and water environments. The PFASs accumulate in atmospheric particulate matters, showing significant concentration variations across regions and seasons, influenced by the industrial activities, population density, and meteorological parameters. Typically, PFASs have a broader spatial distribution with low concentrations during warm seasons, while the pollution levels are higher and concentrated near emission sources in winter. Over the past decade, the concentration of atmospheric PFASs in China has decreased, but their types have significantly increased, mainly due to the impact of policy measures shifting towards the production of PFASs substitutes. Atmospheric PFASs can enter the human body and induce health risks through the exposure pathways of inhalation, skin uptake, and oral ingestion. Currently, inhalation exposure assessment models are mainly used to assess their health risks. Pollution prevention and control measures in developed regions, such as the United States and Europe, have achieved some reduction in PFAS emissions to environment, but they mostly targeted at single substance, and production is gradually moving towards substitutes with unclear risks. Looking ahead, future research on atmospheric PFASs should delve into the transport and transformation mechanisms, synergistic effects and toxicity risks with other pollutants (e.g., particulate matters), establishing long-term monitoring networks and quantitative source apportionment methods, revealing their health effect mechanisms in depth, and developing systematic and comprehensive human health risk assessment models.

Microplastic pollution, as a new type of ecological and environmental problem, is becoming a big challenge faced by the world. The threat and potential risk of microplastic pollution to ecosystem is becoming a hot research topic in the current environmental field. The microplastic-based compound pollution with various pollutants in the environment is more serious than the microplastics pollution alone, so research on the internal mechanism of microplastic composite pollution and the relevant prevention and control strategies taken are more complex than those for microplastic pollution. In this paper, we divided the microplastic-based compound pollution with other pollutants in soil environment into two categories based on the pollution sources, including endogenous pollution (e.g., toxic additive released from microplastic) and exogenous pollution (e.g., heavy metals, persistent organic pollutants, antibiotics). Three main paths of microplastic-based compound pollution in soil were summarized as follows: The first one was microplastics adsorbing common major pollutants, such as heavy metals, persistent organic pollutants, and antibiotics in soil environment; the second one was microplastics forming biofilms with soil microorganisms; the third one was microplastics releasing toxic additives and causing joint pollution. We also analyzed the interaction processes of microplastic pollution with the above-mentioned pollutants and itself-released additives and the relevant influencing factors, as well as their combined ecotoxic effects. Finally, some future research development trends in soil microplastic-based compound pollution areas were presented. This paper aims to provide some references for further understanding of microplastic-based compound pollution in soil and exploring its interaction mechanisms, conducting risk assessments and identifying control strategies.

In order to promote the technology development and progress of the ecological natural restoration and its effective application in the field of national ecological construction, the concept, effects and application conditions of ecological natural restoration are systematically sorted out, and the concept, scope and technical methods of artificial promotion of ecological natural restoration are discussed, and the key directions for further research are prospected, given that the national policy attaches great importance to ecological natural restoration. Through the comparisons of technical points of ecological natural restoration, artificial promotion of natural restoration and artificial restoration, it is suggested that the artificial promotion of natural restoration mode need to take limited artificial treatment measures to improve the efficiency and quality of natural plant restoration. Conventional ecological restoration methods can be regarded as artificially promoted ecological restoration measures, while the degree of manual intervention needs to be defined. The ratio between the proportion of the area under artificial measures and the coverage ratio of the local natural vegetation of the artificial promotion of natural restoration mode should be considered based on the concept of ecological carrying capacity. Therefore, it is necessary to construct two systems of vegetation provenance area and propagation area under the artificially promoted natural restoration mode. The provenance area could provide long-term provenance conditions for the natural restoration of vegetation in the untreated area through the process of vegetation planting area selection, adaptive plant selection and vegetation construction. The roughness of the planting propagation area would be improved through surface micro-topography shaping to promote the interception of natural seeding, plant germination and plant growth. At last, it is expected that research on vegetation establishment, soil improvement, and micro-topography shaping at key nodes, targeted technical research under typical fragile ecological areas or adverse environmental conditions, as well as technical specifications and assessment indicators, will become important research directions for artificial promotion of natural restoration in the future.

Net primary productivity (NPP) is the basis for characterizing the material and energy cycle of the ecosystem, which is one of the important components of regional and global carbon cycle. In order to reveal the spatiotemporal change characteristics and driving mechanism of NPP in China from 2001 to 2020, based on MOD17A3HGF data products, the spatiotemporal change and future development trend of NPP in China were analyzed by Sen trend analysis, Mann-Kendall significance test and Hurst index. The relative roles of climate change and human activities in the process of NPP change were quantitatively analyzed by using correlation and residual analysis methods. The results showed that (1) China’s NPP presented a spatial distribution pattern of high in the southeast and low in the northwest, showing a fluctuating upward trend in time, with an upward rate of 2.86 g·m^-2·a^-1. The spatial change remained unchanged. The area with a significant increase in NPP was significantly larger than the area with a significant decrease. In the future, 84.38% of China's regional NPP will continue to increase or change from a decreasing to an increasing trend. (2) NPP was positively correlated with precipitation and temperature as a whole, of which precipitation had a more significant impact on NPP. The areas with significant positive correlations between NPP and precipitation were mainly distributed in the north of the Yangtze River. The areas with significant positive correlations with temperature were mainly distributed in the central and north of the Qinghai Tibet Plateau, the southeast of the Yunnan Guizhou Plateau, the southeast coastal area and the south of Shandong. (3) Both climate change and human activities played an important role in the NPP improvement areas, but there were significant spatial differences in their relative roles in NPP improvement areas. The vegetation improvement areas dominated by climate change were mainly concentrated in the northeast, north China, Sichuan Basin and the middle and lower reaches of the Yangtze River plain, while the vegetation improvement areas dominated by human activities were mainly concentrated in central, southwest and northwest China. The impacts of climate change and human activities on vegetation degradation were relatively consistent in spatial distribution. The impacts of climate change on NPP degradation areas were slight, but human activities were the main factors causing NPP degradation.

The investigation of the spatio-temporal evolution of PM_2.5 and its associated risk of population exposure holds paramount significance for environmental risk assessment, habitat enhancement, and the development of precise air pollution prevention and control policies by governmental environmental protection agencies. The Weihe River Basin serves as a crucial industrial base of the country and represents an important part of a national urban agglomeration, as well as the Guanzhong-Tianshui national economic zone. Mitigating the risk of population exposure to PM_2.5 in this region is an inevitable step towards high-quality development. Based on remote sensing inversion data of PM_2.5 and population grid distribution data in the Weihe River Basin from 2000 to 2020, the population exposure risk index was calculated. The temporal evolution characteristics of PM_2.5 quality concentration values and population exposure risk indices were identified using the Theil-Sen Median and Mann Kendall tests, respectively. Additionally, the spatial variation characteristics of these variables were analyzed through the utilization of GIS spatial exploration tools. The results showed that (1) the annual average quality concentration of PM_2.5 in the Weihe River Basin was 47.2 μg·m^-3 from 2000 to 2020. The highest value of 57.6 μg·m^-3 was recorded in 2013, while the lowest value of 31.8 μg·m^-3 was observed in 2020. This indicated a trend of initial increase followed by a decrease. Significance testing revealed a decreasing trend in PM_2.5 pollution levels in the Weihe River Basin. (2) The spatial distribution of annual average PM_2.5 quality concentrations exhibited distinct characteristics, with higher values in the eastern region and lower values in the western region. High values were mainly distributed in the lower reaches of the river basin, such as Xi’an, Xianyang and Weinan. Low values were mainly distributed in the middle and upper reaches of the river basin, such as Tianshui City, Dingxi City, Pingliang City, etc. (3) Overall, the risk level of PM_2.5 population exposure in the Weihe River Basin showed a downward trend from 2000 to 2020. However, the average proportion of the population exposed to more than 35 μg·m^-3 over the years was as high as 96.2%. Between 2000 and 2003, as well as from 2005 to 2014, the entire population in the Weihe River Basin experienced exposure to concentrations of 35 μg·m^-3 or higher. Nevertheless, the extent of high-risk areas decreased from 20.6% in 2000 to 17.1% in 2020. (4) The risk level of PM_2.5 population exposure demonstrated a spatial pattern with higher levels in the east and lower levels in the west, displaying significant spatial variation in the Weihe River Basin from 2000 to 2020. Urban built-up areas such as Weicheng, Qindu, and Weiyang predominantly exhibited a “hot spot” type with higher concentrations. Conversely, the “cold spot” type was mainly concentrated in higher elevation areas in the western part of the basin, including Dingxi, Tianshui, and Pingliang. The findings of this study provide a scientific foundation for formulating a collaborative prevention and control policy in managing PM_2.5 pollution within the Weihe River Basin.

Improving regional carbon sink capacity is a key strategic initiative for China's ecological civilization construction, which is an important measure to promote the green transformation of economic and social development. The Taihang Mountains are the significant ecological barrier in North China, and their ecosystems have efficient carbon sink capacity. It is of great significance to study the spatiotemporal differentiation characteristics of carbon storage in the ecosystem of the Taihang Mountains and the driving mechanism of influencing factors to implement the national “dual carbon” project construction in North China, strengthen the regional oxygen release and carbon sequestration capacity, and even comprehensively improve the quality of the regional ecological environment. In this study, based on the land cover and carbon intensity data of the Taihang Mountains in 2005, 2010, 2015 and 2020, the spatial distribution of carbon storage area was estimated with the InVEST model. On this basis, the main driving factors affecting its spatial differentiation were explored by using geographic detectors, and this paper analyzed its driving mechanism. The results showed that: (1) from 2005 to 2020, the land use types in the Taihang Mountains had been changed significantly. The land use area of forest and construction land increased, and the land use area of farmland and grassland decreased. Farmland and grassland were mainly converted to construction land, while some were converted to forests. (2) The total carbon storage in the Taihang Mountains ranged from 1.48×10⁹-1.50×10⁹ t, with an overall gradual increase. From the perspective of land type, the descending order of the proportion of carbon storage showed that forest>farmland>grassland>construction land>water>unused land. The increases of forest and construction land were the main reasons for the increase in carbon storage. (3) The spatial differentiation of carbon storage in the Taihang Mountains was affected by topographic, environmental and soil factors. Based on Geodetector, the influences of NDVI (0.214-0.280) and soil type (0.151-0.160) on the spatial differentiation of carbon storage were significantly greater than those of other factors. The interaction between the driving factors was stronger than that of a single factor, and the strongest synergistic effect was the DEM synergistic NDVI type (0.368-0.406), which indicated that the role of drivers on the spatial variation of ecosystem carbon stocks needs to be considered in the construction of “double carbon”. This study used Geodetector approach to explore the mechanisms of the driving factors of spatial differentiation in ecosystem carbon storage, and provides a new way for research in the field of ecosystem carbon storage.

Organic fertilizer and biochar play an important role in improving soil quality and soil fertility in medium and low yield fields. Five treatments (CK: no fertilization, NPK: chemical fertilizer only, NPK+M: chemical fertilizer+sheep manure, NPK+B: chemical fertilizer+corn straw biochar, and NPK+M+B: combined application of sheep manure and corn straw biochar) were applied to a corn field once at the first crop growing season in a 5-year field experiment. High-throughput sequencing was used for exploring the impact of adding sheep manure and corn straw biochar on soil microorganism community diversity and function in saline-alkali sandy soil of Xinjiang. The results showed that sheep manure and corn straw biochar could improve the physical and chemical properties of saline-alkali sandy soil, reduce soil pH, and increase the cation exchange capacity and nutrient content. NPK+M+B treatment had stronger effects on the organic matter, available phosphorus and available potassium, which were significantly increased by 87.80%, 125.15% and 59.52%, respectively. Fertilization increased soil EC, but NPK+B treatment and NPK+M+B treatment could alleviate the increase. The analysis of microorganism α diversity showed that fertilization increased Shannon diversity index and Chao and Ace abundance index of the bacterial community in saline-alkali sandy soil. NPK+M+B treatment had the best effect, which led to increases by 6.31%, 57.98% and 57.25%, respectively. The application of chemical fertilizer increased the soil fungal diversity, but sheep manure and corn straw biochar decreased the diversity. NPK+M+B treatment could increase the abundance of Actinomycetes which tolerated saline-alkali, drought, antibacterial and oligotrophic, and reduce the community composition and abundance of potential pathogenic fungi significantly. So, NPK+M+B treatment alleviated the risk of soil-borne fungal diseases and improved the microenvironment of saline-alkali sandy soil. A redundancy analysis identified AK, OM, TP, TK and TN, TK, CEC, AN as the major factors that affected the bacterial and fungal community structure and functional groups. PICRUSt functional analysis showed that fertilization could improve the bacterial metabolic function related to stress resistance, such as salt alkali and drought, etc. FUNGuild function prediction showed that NPK+M+B treatment significantly reduced the proportion of pathotroph fungi. Overall, sheep manure and corn straw biochar changes soil physiochemical properties, optimizes the niches of beneficial soil microbiome and suppresses the number of harmful fungi, and thus helps create a stable and healthy soil microecosystem.

Forest ecosystems are an important resource for China to address climate change and implement its intended nationally determined contributions. It is of great significance to scientifically evaluate the impact of the Natural Forest Protection Project on the characteristics of forest carbon sink/carbon source in the implementation area for consolidating and improving the function of forest carbon sequestration and carbon sink enhancement at the regional scale and coordinating regional eco-economy-society coordinated development. Based on the multi-period and multi-type resource survey and statistics data, using the volume-biomass method, the impacts of Natural Forest Protection Project measures (such as artificial afforestation, forest care, wood reduction, forest patrol, etc.) were included in the estimation process to comprehensively evaluate the impacts of Natural Forest Protection Project on the forest carbon pool in the key state-owned forest region of Daxing’anling in Heilongjiang Province, China during 1998-2018. The results showed that (1) through the implementation of the Natural Forest Protection Project, the cumulative net carbon sequestration in the key state-owned forest region of Daxing’anling in Heilongjiang Province had been 1.32×10⁸ Mg in the past 20 years, which was equivalent to offsetting nearly 12% of the cumulative carbon dioxide emissions of Heilongjiang Province in the same period, and compared with industrial measures such as biomass energy and carbon capture and storage, it had obvious cost advantages. (2) Among the various measures, forest carbon sequestration generated by forest management measures was the largest contribution to the net carbon sequestration in the study area, accounting for 80.0%. (3) Due to the uneven spatial distribution of the artificial afforestation area and wood reduction task, the net carbon sequestration in the study area had a certain degree of spatial heterogeneity. (4) The carbon emission and carbon leakage caused by the implementation of the Natural Forest Protection Project had offset part of the forest carbon sequestration benefit, but the offset proportion was only 0.29%, and the overall benefit of forest carbon sequestration and sink enhancement was not affected. For the post-Natural Forest Conservation Project to continuously and steadily play the role of forest carbon pool in the study area, we suggest strengthening the effectiveness of natural forest protection and restoration, avoiding or reducing the disorderly loss of forest carbon pool, innovating the realization path of natural forest carbon sink value, reducing the uncertain impact of measurement and monitoring, and finally realizing the continuous improvement of forest ecosystem carbon sequestration and sink benefits.

Phosphorus is a key biogenic element in lakes, and the transformation is driven by a variety of biochemistry reaction. At the late stage of eutrophication, the acetate produced via alga decaying under anaerobic condition can be used as an organic electron donor in the denitrification process, and iron can be used as an electron donor and energy source in the denitrification process. They can pose direct/indirect effect on the phosphorus transformation by affecting the nitrogen transformation. In this study, a sediment-overlying water system using samples from Lake Moshui of Wuhan was set up, where the driving effect of iron and nitrogen on the phosphorus transformation in the presence of organic electron donors (acetate) was investigated via inputting nitrate, iron and acetate into the overlying water. In the presence of different concentrations of acetate, the changes of nitrogen, phosphorus and iron content in the overlying water and interstitial water with time were firstly investigated, then the denitrification enzyme activity and the abundance of nitrate-dependent Fe(II) oxidation bacteria (NDFOB) in the sediment were determined. Furthermore, the form of phosphorus in sediments was explored to clarify the existence form of iron-bound phosphorus. The results showed: (1) The presence of acetate increased the NDFOB abundance and denitrification enzyme activity in the sediments, increasing the NO₃^--N removal efficiency by 22.6%. (2) There was a significant positive correlation between total phosphorus (TP) concentration and total iron concentration (P=0.001). Easily reducible oxides (Fe_ox1) and reducible oxides (Fe_ox2) were the iron forms with the strongest phosphorus adsorption capacity, accounting for 43.8%-54.1% of the total iron content in sediments. (3) The presence of acetate promoted the reduction of Fe(III) in the sediments. Due to the reduction of Fe_ox1 and Fe_ox2 in the sediments, a relatively high content of Fe(II) was produced, accompanied by a drastic decrease of iron-bound phosphorus content. (4) The content of easily reducible iron-bound phosphorus (P-Fe_ox1) in the final sediments was 0.250 mg·g^-1 lower than that in the NO₃^- treated group. Because the presence of acetate inhibited the formation of Fe_ox2 in the sediments, the content of reducible iron-bound phosphorus (P-Fe_ox2) was 0.010 mg·g^-1 lower than that in the NO₃^- treated group, while the total phosphorus concentrations in overlying water and pore water were significantly higher than those in the NO₃^- treated group (P=0.000). These findings contribute to deepen the understanding of the endogenous pollution theory in lakes by elucidating the transformation of phosphorus-iron binding forms in sediments under different mediation.

Dongjiang Lake is one of the important artificial lakes in the middle and lower reaches of the Yangtze River and the largest drinking water source in Hunan Province. Exploring the changes of water quality and their relationships with land use in the watershed can provide scientific basis for ecological protection of the Dongjiang Lake. Based on the water quality monitoring data in two state-controlled sections from 2011 to 2022 and six major estuaries from 2021 to 2022, using statistical analysis and Spearman rank correlation coefficient method, the spatio-temporal changes of water quality in Dongjiang Lake and their relationships with land use change were illustrated.The results showed that (1) during the recent 12 years, the comprehensive index of water environmental pollution in Dongjiang Lake showed an increasing trend and the water quality has decreased from surface Ⅰ to surface Ⅲ over time. The surface water quality in the major estuaries of Dongjiang Lake was between level Ⅲ and Ⅳ and the comprehensive index of water environmental pollution in the estuaries was higher in dry season than in wet season. (2) The area of each land use type in Dongjiang Lake basin followed the order of forest land>cultivated land>water area>construction land>grassland. During the period from 2011?2022, the area of construction land, cultivated land, and grassland increased with the increase in time and the area of forest land and water decreased with the increase in time. (3) The COD, COD_Mn, EC, and water pollution index in state-controlled sections in Dongjiang Lake were positively correlated with the area of cultivated land and construction land and negatively correlated with the area of forest land. However, the DO in the six estuaries was positively correlated with the water area in sub-watersheds in Dongting lake. It can be concluded that the water quality in Dongjiang Lake decreased during the period from 2011 to 2022 and the increase in cultivated land and construction land area and the decrease in woodland area in the basin were the key reasons for the decrease in water quality. Therefore, reducing in use of chemical fertilizer in the whole watershed, facilitating full coverage of urban sewage treatment facilities, continuous implementation of returning farmland to forests or grassland and the ecological restoration in water fluctuation zone of river and lake are recommended to reduce pollutants into the lake and ensure clean water in the Dongjiang Lake.