Temporal-spatial variation and regulatory mechanism of carbon budgets in territorial space through the lens of carbon balance: A case of the middle reaches of the Yangtze River urban agglomerations, China

As China’s largest cross-regional urban agglomerations, the middle reaches of the Yangtze River urban agglomerations (MRYRUA) possess both significant societal carbon source volume and ecological carbon sequestration capacity. Nevertheless, with the uncontrolled expansion of urban energy consumption activities and the industry migration from eastern coastal regions to inland cities, the carbon budget pattern of territorial space is increasingly unbalanced in the MRYRUA. To achieve low-carbon regulation, this study utilized land use and energy consumption data from 31 cities within the MRYRUA to establish a “carbon source-carbon sink” quantification and spatiotemporal exploration model, revealing the spatial-temporal variation of carbon budgets from 2005 to 2020. Furthermore, we developed a carbon balance indicator analysis system by employing the carbon offset rate (COR), carbon productivity (CP), Gini coefficient, ecological support coefficient (ESC), economic contribution coefficient (ECC), and functional zoning was performed. Finally, using the GM (1,1) model, we derived the carbon budget pattern for 2050 and explored the differentiated regulatory mechanisms under the carbon balance perspective. The results indicated that: (1) The MRYRUA’s territorial carbon budgets have increased annually, displaying a spatial distribution pattern with the highest values in the central region, followed by the northwest, and the lowest in the southeast near water bodies. The spatiotemporal differentiation effects manifest as an east–west axial development trend, with spatiotemporal clustering effects demonstrating a propensity for outward dispersion from the northern hot spot radiation core. (2) The MRYRUA’s COR has consistently remained below 10% and decreased annually, while the CP has shown a yearly increase at an accelerating rate. The ESC and ECC exhibit evident spatial heterogeneity among cities. In response to the carbon emission economic benefits and carbon sequestration ecological carrying capacity reflected by carbon balance indicators, each city was classified into low-carbon economic zones, carbon intensity control zones, carbon sink functional zones, and high-carbon optimization zones. (3) From 2020 to 2050, the polarization trend of the carbon budget pattern continues to intensify. Subsequently, we have established a differentiated territorial spatial carbon balance regulatory mechanism. This mechanism strengthens the leading role of low-carbon economic zones in the green low-carbon transition, moderately retains the carbon sink functional zones in the southeast with solid carbon fixation capabilities, and promotes the transition of the northern carbon intensity control zones and high-carbon optimization zones to low-carbon economic zones. The research findings provide a scientific basis for formulating territorial spatial planning policies from a carbon neutrality perspective

Assessment and Management Zoning of Ecosystem Service Trade-Off/Synergy Based on the Social–Ecological Balance: A Case of the Chang-Zhu-Tan Metropolitan Area

Clarifying the trade-offs/synergies of ecosystem services is crucial for achieving a win-win situation in economic development and ecological conservation. Past studies have lacked research on ecosystem service functional management zones that integrate socio-economic factors and ecological conservation, particularly based on predictive scenarios. Based on the above, this study innovatively established a multi scenario simulation model and framework (EST-EMZ) for the study of ecosystem service (ES) trade-off/synergy and ecological management zoning, combining remote sensing and socio-economic data from 2000 to 2020 in the Chang-Zhu-Tan Metropolitan Area (CZTMA). The model evaluates the dynamic trade-offs/synergies among different ecosystem services under various scenarios, aiming to seek the optimal management approach for enhancing the functionality and optimizing the structure of ESs in the future of the CZTMA. The results indicate the following: (1) From 2000 to 2020, the Ecosystem Service Value (ESV) of the CZTMA gradually declined from 601.57 billion yuan to 584.65 billion yuan. Under the three future scenarios, the ESV also decreased, with the Ecological Conservation Scenario (ECS) experiencing the most minor decline, and the Economic Priority Scenario (EPS) witnessing the most substantial decrease. (2) In the historical period and the 2030 predicted scenarios, there is a predominant synergy among paired ESs in the CZTMA. Throughout the study period, the region’s dominant ecosystem service bundle (ESB) is the high-service ecological regulation bundle, primarily located in the northeastern, western, and southern areas dominated by forests. (3) Based on ESV and urbanization intensity (UI), five different ecosystem management zones were identified: water balance zone (WBZ), coordinated improvement zone (CIZ), ecologically weak zone (EWZ), ecological conservation zone (ECZ), and ecological derivative zone (EDZ). Corresponding management and protection strategies for ecosystem services were proposed. The research findings offer potential solutions for optimizing land use and managing the trade-offs of ESs in metropolitan areas

Human Settlement Resilience Zoning and Optimizing Strategies for River-Network Cities under Flood Risk Management Objectives: Taking Yueyang City as an Example

The dense river network and large population in the southern region of China are vulnerable to flooding stress, which challenges the construction of human settlements. This paper analyzes the causes of flood risk and the dilemma of human settlement improvement in river-network cities, introduces the principle of resilience to human settlements, and conducts a quantitative study on the resilience of human settlements in river-network cities with the goal of flood risk management. Taking Yueyang city, a river-network city in the Yangtze River Basin, as the empirical research object, we conduct a flood resilience zoning of the human settlements based on the flood risk assessment model and use the GIS spatial overlay method to correct the resilience of the current human living space against the territorial spatial planning of Yueyang city. Ultimately, we propose a strategy for optimizing human settlements under flood risk management. The results show that (1) the highest-risk and high-risk areas of Yueyang city were mainly located in Dongting Lake and its interconnected water system, the southwest local area and the southeastern fringe, while the low-risk and lowest-risk areas were mainly located in the northeast local area and the northwestern fringe, with low flood stress risk. (2) The spatial system of human settlement resilience was constructed based on the flood risk assessment level. Among them, the human settlement flood resilience zoning of Yueyang city was divided into five categories from low to high: human settlement control zone, restriction zone, buffer zone, construction zone and expansion zone; the flood resilience zoning of Yueyang city’s current living space was divided into three categories from low to high: structure adjustment zone, flood restriction zone and development stability zone. (3) The specific control implementation and execution of the human settlements in Yueyang city mainly focus on the interrelationship between the risk of flooding in the watershed and the development of human activities through zoning regulation and collaborative management to optimize the human settlements. The study results can provide positive intervention and guidance for constructing urban and rural territorial spatial prevention planning and improving human living quality in river-network cities in China

Water-Town Settlement Landscape Atlas in the East River Delta, China

The water-town settlements in the East River Delta of China engage with the aquatic environment, establishing a comprehensive cultural–ecological system. However, rapid urbanization challenges the structural integrity of water-town settlements. Focusing on the East River Delta as the study area, we utilized the Normalized Difference Water Index (NDWI), settlement morphology indicators, systematic clustering, and graph classification methods. We conducted a quantitative analysis of the spatial characteristics of water-town settlements at various scales, followed by formulating a sequence encoding based on landscape factors and constructing a settlement landscape spatial map. We characterized the landscape spatial structure of water-town settlements formed through the gradual evolution of morphological water network structures, retracing a prototype of water-town settlement landscape spatial structures. Results: ① Water-town settlements exhibit distinct uniformity in the landscape spatial features. The settlement landscapes conform to water network patterns, with streets and alleys aligning with water bodies. Crucial elements, including docks, bridges, and waterside farmland, are integral to this landscape. ② Water-town settlements undergo three progressive differentiation phases based on their location. The spatial distribution of settlements reveals three distinct landscape features influenced by the delta’s dynamic interplay between water and land. ③ Various regions exhibit three typical settlement layouts: upstream settlements are mainly clustered and linear, while midstream and downstream settlements, characterized by linear and strip-like features, align with the river’s course. These research findings offer preliminary insights into landscape spatial prototypes, contributing valuable perspectives to the conservation and design of water-town settlements

Large-scale material extrusion-based additive manufacturing of short carbon fibre-reinforced silicon carbide ceramic matrix composite preforms

Large-scale short carbon fibre-reinforced silicon carbide (Csf/SiC) ceramic matrix composites (CMCs) have important applications in the field of aerospace engineering. This study proposed the use of material extrusion based additive manufacturing to fabricate large-scale Csf/SiC CMC preforms. In this paper, we determined how the key material extrusion parameters, including solid loading, nozzle diameter and layer height impact the stability of the additively manufactured Csf/SiC CMCs. The solid loading significantly influenced the stability of the Csf/SiC CMCs, and the slurry with 50 vol.% solid loading was better for additive manufacturing. The layer height played a significant role in the void formation in CMCs. It was appropriate for structure retention to set the layer height as 60–75% of the nozzle diameter. The effect of angle from vertical on the stability of out-of-plane structure was also investigated. When the angle was over 40o, the out-of-plane structure additively manufactured without supports tended to collapse. Large-scale Csf/SiC CMC preforms with out-of-plane structures were finally successfully fabricated. This study is believed to provide some fundamental understanding for the fabrication of large-scale fibre-reinforced ceramic matrix composites

Human GLP-1 receptor transmembrane domain structure in complex with allosteric modulators

The glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR) are members of the secretin-like class B family of G-protein-coupled receptors (GPCRs) and have opposing physiological roles in insulin release and glucose homeostasis. The treatment of type 2 diabetes requires positive modulation of GLP-1R to inhibit glucagon secretion and stimulate insulin secretion in a glucose-dependent manner. Here we report crystal structures of the human GLP-1R transmembrane domain in complex with two different negative allosteric modulators, PF-06372222 and NNC0640, at 2.7 and 3.0 Å resolution, respectively. The structures reveal a common binding pocket for negative allosteric modulators, present in both GLP-1R and GCGR and located outside helices V-VII near the intracellular half of the receptor. The receptor is in an inactive conformation with compounds that restrict movement of the intracellular tip of helix VI, a movement that is generally associated with activation mechanisms in class A GPCRs. Molecular modelling and mutagenesis studies indicate that agonist positive allosteric modulators target the same general region, but in a distinct sub-pocket at the interface between helices V and VI, which may facilitate the formation of an intracellular binding site that enhances G-protein coupling