Quantitative identification on spatial mismatch characteristics between supply and demand of carbon sequestration services.

Exploring the mismatch between supply and demand (SD) for carbon sequestration services (CSS) is essential for achieving the "double carbon" goal. However, more studies are needed on the traits of the spatial mismatch between SD in mountainous cities. We used the CASA model and the IPCC emission factor approach to address this issue and quantify the SD of CSS in Chongqing. Second, we established a matching relationship model for the SD of CSS in Chongqing. Finally, we applied the Structural Equation Model with the Partial Dependence Plots model to reveal the influencing factors and internal mechanisms of spatial mismatch between the SD of CSS in Chongqing. The outcomes confirmed a decrease in fashion in the total supply of CSS in Chongqing and growth in fashion in general demand from 2000 to 2020. The SD mismatch was mainly concentrated inside the central city and other built-up areas. The SD mismatch area had increased by 390%, indicating a continuous upward trend. In exploring the factors influencing the mismatch between the SD of CSS in Chongqing, supply is mainly positively influenced by NDVI, and demand and supply-demand relationships are influenced by population density and LUCC. We proposed policy suggestions to alleviate the spatial mismatch and practical significance for achieving the "double carbon" goal and promoting sustainable development.

An ecological scenario prediction model for newly created wetlands caused by coal mine subsidence in the Yanzhou, China.

The ecological model we developed can simulate the state of wetlands and predict ecosystem development by varying both parameter settings and forcing functions. The newly created wetland resulting from large-scale coal mining is a distinct type of wetland, but existing ecological models for this wetland type are limited in number and scope. The Yanzhou coalfield, located in Shandong Province in China, contains a typical newly created wetland that came into being after coal mining subsidence. We developed an ecological model for this wetland that estimates values for four state variables: phytoplankton biomass (A), zooplankton biomass (Z), sediment biomass (D), and hydrophyte biomass (H). Analysis of the results showed that the model was sensitive to changes in nutrient loading. As nutrient loads increased, plankton biomass increased, and the ratio of zooplankton biomass to phytoplankton biomass (Z/A) decreased. We defined three prediction scenarios for the wetland and calculated their eco-exergies to compare the ecological effects for each scenario. The most effective measures to improve the state of the ecosystem are to reduce the subsidence depth and to decrease nutrient loading.

Spatiotemporal evolution trend and decoupling type identification of transport carbon emissions from economic development in China.

Carbon emissions are a major concern in China, and transportation is an important part of it. In this paper, data on China's 30 provinces' transport carbon emissions from 2005 to 2019 were selected to construct a spatial autocorrelation model and identified the decoupling types, which revealed the relationship between transport carbon emissions and economic development. This study suggests a regulation strategy for provincial transport carbon emissions in China based on the contribution rates of transport carbon emission variables. According to the findings, transport carbon emissions of China indicated a slow rise from 2005 to 2019, the annual growth rate has fluctuated downward, and petroleum products have been the most major source. The geographical correlation of transport carbon emissions has gradually improved, and the transport carbon emission intensity has become more significant. Differences in the transport carbon emission intensity slightly increased, which were significantly regionally correlated. There were seven forms of decoupling between yearly provincial transport carbon emissions and economic development, with weak decoupling accounting for the largest proportion, 45.24%. Decoupling was achieved in 83.33% of the provinces in the period of 2005-2019. As a consequence of factor decomposition, the energy intensity, transport intensity, and economic structure played an overall inhibitory role, while the carbon emission intensity, economic scale, and population played promoting roles. The economic scale was the most important influencing factor.

How can multiscenario flow paths of water supply services be simulated? A supply-flow-demand model of ecosystem services across a typical basin in China.

Ecosystems provide many benefits to humans, and among them, water supply is crucial for human survival and development. This research focused on the Yangtze River Basin as the research area, quantitatively evaluated the temporal-spatial dynamic changes in the supply and demand of water supply services and determined the spatial relationship between the supply and demand regions of water supply services. We constructed the supply-flow-demand model of water supply service to quantify its flow. In our research, the Bayesian model was used to establish a multiscenario model of the water supply service flow path to simulate it and clarify its spatial flow path, flow direction and flow magnitude from the supply region to the demand region and determine its changing characteristics and driving factors in the basin. The results show that (1) In 2010, 2015 and 2020, the amount of water supply services showed a decreasing trend and was approximately 133.57 × 1012 m3, 129.97 × 1012 m3 and 120.82 × 1012 m3, respectively. (2) From 2010 to 2020, the trend of the cumulative flow of water supply service flow decreased each year and was 59.814 × 1012 m3, 56.930 × 1012 m3, 56.325 × 1012 m3 respectively. (3) Under the multiscenario simulation, the flow path of the water supply service was generally the same. The proportion of the water supply region was the highest under the green environmental protection scenario, at 73.8 %, and the proportion of the water demand region was the highest under the economic development and social progress scenario, at 27.3 %. (4) The provinces and municipalities in the basin were divided into three types of regions according to the matching relationship between supply and demand: catchment region, flow pass-through region and outflow region. The number of outflow regions was lowest, accounting for 23.53 %% of the regions, while the number of flow pass-through regions was the highest, accounting for 52.94 %.

Constraint relationship of ecosystem services in the Yangtze River Economic Belt, China.

Understanding the relationship among ecosystem services (ESs) is essential to promote ESs management and sustainable development. The relationship between ESs is mutual and can be expressed in terms of trade-offs, synergy, and constraints. The paper selected the InVEST model to assess the water yield (WY), soil conservation (SC), food production (FP), net primary productivity (NPP), and habitat quality (HQ) of the Yangtze River Economic Belt (YREB) and used the constraint line method to analyze the relationship of paired ecological services at three scales: landscape, watershed, and land category. The following conclusions were drawn: (1) during the study period, the spatial changes of the five ecological services in the YREB did not change much, but the spatial distribution of the ecological services was different. (2) From 2000 to 2015, the constraint line of YREB paired ecological services had a high degree of fit. Under the three levels of landscape, watershed, and land category, the YREB has a variety of constraint types, including negative lines, logarithms, paraboloids, humped shapes, and rectangles. (3) At the three levels, the constraint lines between FP, NPP, WY, and SC and HQ were stable rectangular constraints; WY-SC was hump shaped, FP-NPP, FP-SC, FP-WY, NPP-WY, and NPP-SC changed with the scale, showing different spatial scale changes. (4) The paired ESs directly determined the ecological constraint curve but under the combined effect of other factors, which would affect or change the constraint line. We discussed the effects of weather, topography, and economy on the constraint relationship, and found that all have different degrees of influence.

Integrating ecosystem services and landscape connectivity to construct and optimize ecological security patterns: a case study in the central urban area Chongqing municipality, China.

Rapid urbanization is often accompanied by the irrational utilization of natural resources and environmental degradation. Ecological security pattern (ESP) is an effective way for rational allocation of resources, which is conducive to achieving sustainable development. Taking the central urban area Chongqing municipality as the study area, ecological sources were identified by integrating ecosystem services and landscape connectivity. Combining natural and anthropogenic factors, a resistance surface was constructed and modified, and four ecological function zones were determined. Ecological corridors were extracted and prioritized by Linkage Mapper and the gravity model, and ecological nodes were also obtained. A network connectivity assessment was performed to compare the connectivity of ESPs before and after optimization. The results showed that ESPs included 2453.72 km2 of ecological sources, 189 ecological corridors, 69 ecological nodes and 4 ecological function zones. The ecological sources primarily consisted of forestland, cultivated land and water bodies in Jinyun, Zhongliang, Tongluo, Mingyue and other mountainous areas, with the maximum distribution index value at the tenth level of the terrain niche index gradient. The Yangtze River and Jialing River were also the most important ecological sources. Ecological corridors were mainly dominated by forestland and cultivated land. Ecological nodes were concentrated in Yubei, Banan and Jiulongpo districts. The optimized ESPs had higher network connectivity and closure, with a more uniform distribution of ecological corridors, and included 2461.95 km2 of ecological sources, 218 ecological corridors and 72 ecological nodes. Finally, recommendations for sustainable development were proposed. This study provides a theoretical reference for decision-making related to ecological protection and urban planning.

How can an ecological compensation threshold be determined? A discriminant model integrating the minimum data approach and the most appropriate land use scenarios.

Ecological compensation has become very common worldwide due to the imbalance in the development of modern society, economy, and the environment and the increased pressure on ecosystem carrying capacity. Nonetheless, the various approaches for quantifying ecological compensation standards differ significantly. Thus, the process for determining a reasonable ecological compensation threshold is important to understand. To ensure the maximization of ecosystem service supply and economic benefit incentives for farmers, this paper constructs a discriminant model of an ecological compensation threshold based on the minimum data approach and the most appropriate land use scenario to define the ecological compensation threshold of the Sloping Land Conversion Program in the upper Yangtze River basin. The results show that with an increase in the compensation price, the proportion of farmers participating in returning farmland to forests and grassland increases, and water conservation increases. However, the discriminant curve first increases to a certain threshold point and then decreases, after which the ecoefficiency rate obtained from the compensation decreases. The ecological compensation thresholds for Chongqing, Sichuan, Yunnan, Guizhou, Hubei, Qinghai, Gansu, Tibet and Shaanxi provinces are 17.74 yuan/m3, 13.79 yuan/m3, 19.1 yuan/m3, 17.79 yuan/m3, 15.28 yuan/m3, 45.14 yuan/m3, 17.23 yuan/m3, 25.2 yuan/m3 and 22.36 yuan/m3, respectively. This research examines ecological compensation standards in different watersheds throughout the world and discusses the relationship between ecological compensation and water conservation. The discriminant model of the ecological compensation threshold can provide a new reference for the implementation and management of ecological compensation policies.

Diversity and Distribution of Riparian Arthropods in the Drawdown Zone of China's Three Gorges Reservoir.

Riparian zones are interesting habitats as they are important transitional zones between terrestrial and aquatic ecosystems, but highly threatened by human disturbances. They support a high arthropod diversity as they experience periodic flooding disturbance and sharp environmental gradients. Their associated arthropod fauna are of high conservation value. Nevertheless, their arthropod diversity remains largely unknown, and its distribution pattern along elevational gradients is poorly understood. Few data are available on the effects of flood regimes and other factors in determining riparian arthropod communities. In this study, we investigated the diversity and distribution of riparian arthropods along an elevational gradient and determined the major factors structuring the arthropod communities in the drawdown zone of the Three Gorges Reservoir, China. Significant compositional and structural changes of riparian arthropod communities were observed along the test elevational gradient. The abundance and richness of riparian arthropods increased with elevation. The relative abundance of predators decreased with elevation, whereas the saprovores and omnivores showed an upward trend along the elevational gradient. Redundancy analysis showed that there were significant interactions between the flood regimes, plant communities, and soil conditions. Among these environmental factors studied, flood duration was the main factor in structuring the riparian arthropod communities. Conservation and restoration strategies should consider flood duration in the operation of large reservoirs because riparian arthropods are particularly sensitive to flood regimes.

CH4 concentrations and fluxes in a subtropical metropolitan river network: Watershed urbanization impacts and environmental controls.

Urbanization and greenhouse gas emissions are of great global concern, especially in developing countries such as China. However, little is known about the relationship between the two. In this study, we examined the influences of the urbanization of Chongqing Municipality, which covers an area of 5494km2, in China, on the CH4 emissions of in its metropolitan river network. The results from 84 sampling locations showed an overall mean CH4 concentration of 0.69±1.37µmol·L-1 and a CH4 flux from the river network of 1.40±2.53mmolCH4m-2d-1. The CH4 concentrations and fluxes presented a clear seasonal pattern, with the highest value in the spring and the lowest in the summer. Such seasonal variations were probably co-regulated by the dilution effect, temperature and supply of fresh organic matter by algal blooms. Another important result was that the CH4 concentrations and fluxes increased with the degree of urbanization or the proportion of urban land use, being approximately 3-13 times higher in urban and suburban areas than in rural ones. The total nitrogen, dissolved oxygen (O%) and possible sewage discharge, which could affect the in situ CH4 production and exogenous CH4 input respectively, were important factors that influenced the spatial patterns of CH4 in human-dominated river networks, while the nitrogen (N) and phosphorus (P) could be good predictors of the CH4 emissions in urban watersheds. Hydrologic drivers, including bottom sediment type, flow velocity and river width, were strongly correlated with the CH4 concentrations and could also affect the spatial variance and predict the CH4 hotspots in such metropolitan river networks. With increasing urbanization, we should pay more attention to the increasing greenhouse gas emissions associated with urbanization.