Heavy metal pollution of farmland soils is a serious environmental problem. The accurate estimation of heavy metal pollution levels of farmland soils is very crucial for sustainable agriculture. Concentrations of heavy metal elements (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in farmland soils at 186 sampling sites in the Baghrash Lake Basin, NW China, were determined and analyzed based on the pollution index (P_i), the geo-accumulation index (I_geo), the enrichment factor (EF), the ecological risk index (ER), and the environmental risk index (I_er). The results of these five different estimation methods were compared and discussed. The obtained results indicated that the average concentrations of all the heavy metals in the farmland soils of the study area were lower than the Soil Environmental Quality of China (GB 15168–2018) levels, but the average concentrations of Cd, Cr, Ni, Pb, and Zn exceed the corresponding background values. Significant differences in estimation results existed between the five estimation methods. Based on the identified concentrations, the average P_i, I_geo, and EF values of the heavy metals in farmland soils decreased in the order of: Zn > Pb > Cd > Cr > Ni > Cu > As, whereas the average ER values decreased in the order of: Cd > As > Cu > Pb > Ni > Cr > Zn, and the average I_er values decreased in the order of: Cd > Cu > Zn > As = Pb > Cr > Ni. The pollution class values with different estimation methods were ranked as: P_i > I_geo = EF > ER = I_er. The obtained results suggest that the most appropriate estimation method and soil background values of farmlands should be used for better understanding the environmental quality of farmland soils. Overall, the EF and ER methods are recommended for assessing heavy metal pollution risks of farmland soils.

The values of farmland ecosystem services are composed of several components: provisioning service value, regulating service value, supporting service value and cultural service value, so it is important to make a full assessment of the values of farmland ecosystem services for agriculture and farmland protection. Here, we assessed the values of farmland ecosystem services in Qingdao City in 1997, 2002, 2007, 2012 and 2017 by using various methods (market value method, carbon tax method, afforestation cost method, substitute cost method, equivalent factor method, etc.) based on establishing an assessment index system for the farmland ecosystem services value. The results show that the total yearly value of farmland ecosystem services increased from 499.74×10⁸ Yuan to 681.74×10⁸ Yuan in the period of 1997–2017, and the yearly value of farmland ecosystem services per hectare increased from 6.57×10⁴ Yuan to 9.73×10⁴ Yuan. The product provisioning service, carbon fixation service and oxygen release service, as well as the soil conservation service, are the main farmland ecosystem services, and the proportions of these four ecosystem service values to the total value of farmland ecosystem services in Qingdao City were large and kept increasing. Some countermeasures are put forward to adequately use the indirect service value of the farmland ecosystem and provide improved well-being for humans, such as protecting and wisely using farmland, developing agriculture that is rooted in local conditions, promoting agricultural production efficiency, speeding up construction of modern agriculture gardens, deepening the supply-side structural reform of agriculture, developing agricultural eco-tourism, etc.

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon (MBC) and nitrogen (MBN) contents and their seasonal dynamics in five forest types (a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon (TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.

In order to provide a theoretical basis for the protection and development of T. ciliata germplasm resources, we studied the genetic diversity of T. ciliata by using SSR (Simple Sequence Repeat) primers to evaluate the genetic diversity of 192 T. ciliata germplasm samples from 24 populations of 5 provinces. DataFormater, Popgene, NTSYS, TFPGA and other software were used for genetic data conversion, genetic parameter estimation, dendrogram construction and genetic variation analysis. The results showed that: 1) a total of 17 alleles (N_a) were detected in seven pairs of primers, with an average of 2.260 for each primer. Among them, the highest numbers of alleles (4) were detected in primers S11 and S422.The mean value of Nei's genetic diversity index (H) was 0.4909, the mean value of Shannon information index (I) was 0.7321, and the mean value of polymorphic information content (PIC) was 0.5182. The mean expected heterozygosity (H_e) and observed heterozygosity (H_o) were 0.1055 and 0.4956, respectively. The Nei′s genetic distances of the populations ranged between 0.0002 and 2.6346, and the mean was 0.5477. The average genetic diversity level (H=0.1044) of the 24 populations was lower than that of the species (H=0.4909). 2) The genetic differentiation coefficients (F_st) varied from 0.2374 to 0.9148, with an average value of 0.7727. The mean of population gene flow (N_m) was 0.0735, indicating a low level of genetic exchange between populations, and suggesting that the genetic variation mainly came from within populations. 3) With the UPGMA method, the 24 populations were clustered into 3 groups at Nei's genetic identity (0.99): the populations from Guizhou Province and Guangxi Zhuang Autonomous Region were clustered into one group, the populations from Hunan Province were in another group, and the populations from Hubei Province were in the third group. The Mantel test analysis showed a significant correlation between Nei's genetic distance and geographic distance (r=0.6318, P=0.009<0.05). The genetic diversity of the 24 populations of T. ciliata was at a low level. Geographic isolation was the main reason for genetic differentiation among T. ciliata provenances. In the protection of germplasm resources of T. ciliata, emphasis should be placed on breeding genetic resources from the populations with higher genetic diversity (P14, for example). As for the populations with low genetic diversity, an ex-situ protection strategy as well as ecological and timber objectives, should be taken into account to maximize the conservation and utilization of the diversity of T. ciliata.

The widening gap between the supply and demand levels for livestock and poultry products in the Chinese mainland poses a significant challenge to the secure supply of feed grains. Therefore, the accurate prediction of the demand potential for feed grains represents a key scientific issue for ensuring food security in the Chinese mainland. This study is based on an analysis of several factors, such as the Chinese mainland's output, trade volume, apparent consumption of livestock and poultry products, and two different scenarios for predicting the future demand for feed grains are assessed. The results indicate that output and consumption of livestock and poultry products, as well as the country's trade deficit and the pressure of the supply and demand balance with respect to these products, have been increasing in recent years. The analysis predicts that the demand for feed grains in the Chinese mainland will reach 425.5 or 389.6 million tons in 2030 based on the two scenarios. This finding indicates that with the increasing demand for livestock and poultry products in the Chinese mainland, the demand for feed grains will continue to increase, and the shortfall in feed grains and raw materials will expand further, especially dependence on external sources of protein-rich feed grains will remain high.

An accurate understanding of the real situation of energy-related carbon emissions and the main factors driving the carbon emissions increments are crucial for China to realize its emission mitigation targets. Adopting the comparative decomposition of an extended LMDI (Log-Mean Divisia Index) approach, this study decomposed the changes in carbon emissions of Jiangsu, Henan, and Inner Mongolia, which are located in the eastern, central and western parts of China. This analysis led to three main findings. 1) During the period of 1996–2017, the energy-related carbon emissions in the examined provinces exhibited upward trends, but with some differences among the provinces. 2) The influences of driving factors on carbon emissions varied distinctly in different provinces and economic stages. Economic growth had the largest positive effect on provincial carbon emissions increases. From 1996 to 2017, the contribution rates of economic development to emissions growth in Henan, Jiangsu and Inner Mongolia were 307.19%, 205.08% and 161.26%, respectively. This influence was followed by urbanization and population size. 3) Energy intensity played a leading role in facilitating emissions-reduction in the examined provinces, except for during the tenth Five-Year Plan, followed by the energy structure. The effect of rural population proportion was the weakest among all the curbing factors. Furthermore, urban and rural resident′s energy consumption per capita demonstrated relatively minor impacts and disparate directions of influence in the different provinces and economic periods, but began to play increasing roles in driving up provincial emissions changes. For example, residential energy consumption in Jiangsu contributed over 7.9% to the total carbon emission growth in 1996-2017, among which urban residents' per-capita energy consumption contributed more than 3.8%. In view of these findings, policy makers should formulate targeted emission reduction measures that are based on the distinct situations and key factors which affect carbon emissions in each province.

The fragility of ecosystem health has become a key factor hindering the sustainable development of the ecological environment. Through a review of published research from domestic and foreign scholars, starting from the endogenous logic of studies in the field of ecosystem vulnerability (EV), this paper sorts out the literature on the aspects of measurement models, prediction methods and risk assessment, comprehensively defines the research category and scientific framework of EV, and analyzes the research ideas and development trends. We arrived at the following conclusions: 1) The connotation of ecosystem vulnerability not only embodies the change in the vulnerability of the natural environment, but it also reflects the irreversible damage to the ecosystem caused by excessive development and industrial production activities. 2) The setting of ecosystem vulnerability indices should aim to fully reflect the essential features of that vulnerability, which should include the index systems of natural, social, economic and other related factors. 3) There are many types of ecosystem vulnerability measurement methods, prediction models and risk evaluation models, which have different focuses and advantages. The most appropriate method should be adopted for conducting comprehensive and systematic evaluation, prediction and estimation according to the different representation and evolution mechanisms of the chosen research object and regional ecosystem vulnerability. 4) Based on the regional system characteristics, corresponding risk management measures should be proposed, and pertinent policy suggestions should be put forward to improve the ecological safety and sustainable development of an ecologically vulnerable area.

Urban surface soil has a unique set of structures and processes that affect surface soil organic carbon density (SOC_density) and its spatial variations. Using Beijing as a case study, and assisted by field investigations and experiments, we analyzed the spatial distribution of SOC_density in different land use types and functional regions, and assessed associated factors such as urbanization level, the physiochemical properties of soil and plant configurations. The present study aims to provide useful information about the mechanisms driving soil organic carbon and climate change in developing and developed areas in urbanized regions like Beijing. Results indicate that P is the main factor positively influencing SOC_density in most regions. Because of the specific interference directly related to human beings in urban areas, with decreases in the urbanization level, more physiochemical factors of soil can influence SOC_density. SOC_density under grasses is not significantly different from that under other plant compositions. Urbanization processes decrease the heterogeneity of the spatial pattern of SOC_density in most land use types, but increased its contents when the area reached a developed level in Beijing. More factors related to human interference and spatial variation of surface soil carbon storage, especially under impervious land in urban areas, should be considered in future studies.

The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming (beginning in 2008) on nutritional quality in three alpine meadows (site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude ash (Ash), ether extract (EE) and water-soluble carbohydrate (WSC) were examined in 2018–2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture (SM). The content of CP decreased with vapor pressure deficit (VPD). The combined effect of SM and VPD was greater than air temperature (T_a) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to T_a, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet.

Phytoremediation technology using aquatic plants is being used increasingly in constructed wetlands to purify wastewater. The physiological responses of water lettuce (Pistia stratiotes) and its effectiveness in removing fluoride (F⁻) from water are described in this article. The results indicate that Pistia stratiotes has the ability to accumulate F⁻. The removal efficiency ranged from 27.79% to 56.32% for the various initial F⁻ concentrations tested, and was highest (56.32%) in the highest initial concentration group 60mg/L. The F⁻ concentrations in control groups (without Pistia stratiotes) changed very little, from –1.135% to –0.007% of the initial concentrations. At the highest removal rate, the bioconcentration factor was 7.84. The rate of purification conformed to the Michaelis-Menten equation, and the correlation coefficients (R²) were all greater than 0.97. The Specific Growth Rates (SGR) of the treatment groups were –8.03% to –1.22%, and the SGR of plants under F⁻ stress decreased during the experimental period. The partial correlation analysis showed that concentrations of F⁻ in water were strongly linearly correlated with peroxidase.

With the emergence of the concept of cultural routes, researchers have increasingly turned their attention to the sustainable development of tourism along cultural routes. The needs for community participation and the ongoing provision of benefits of stakeholders are characteristics of cultural routes. Therefore, the importance of cooperative relations and systematic development among stakeholders in tourism activities along cultural routes has become a subject of interest. This paper selects local government, tourism enterprises and local community residents, all of which play a key role in the Ancient Tea Horse Road cultural route in the south of Yunnan, as the main stakeholders. We use game theory to construct a model to trace interactions between local government and tourism enterprises, between tourism enterprises and community residents, and between local government and community residents. The paper then analyzes the different interests of the three parties and key factors that influence them in the game process. This provided a certain scientific basis for the win-win decisions regarding tourism development made by the three parties. Our results show that the final decision choices of the three parties depend on the initial payoff matrix of the game, and the influence of key parameters. When making decisions about tourism, the government should respect the wishes of local residents, strengthen protections of local traditions, manage the unreasonable behavior of tourism enterprises as they develop tourism, and develop appropriate penalties for violations of regulations. When tourism enterprises carry out tourism development, they should let community residents take the initiative and fully participate in tourism activities, and be sure that income from tourism is fed back to local residents, to ensure that tourism is mutually beneficial. The study shows that conflicts among the three parties originated mainly from differences in interests, but that the three parties also shared common interests. With a goal of coordinating interests, we can establish relevant mechanisms, follow the principle of interest realization, attach importance to supervision and management, strengthen community participation and decision-making, and realize win-win results for the three parties.