Search Results (150)

Land cover, topography, precipitation, and socio-economic factors exert both direct and indirect influences on urban land surface temperatures. Within the broader context of global climate change, these influences are magnified by the escalating intensity of the urban heat island effect. However, the interplay and underlying mechanisms of natural and socio-economic determinants of land surface temperatures remain inadequately explored, particularly in the context of cold-region cities located in the northern temperate zone of China. This study focuses on Changchun City, employing multispectral remote sensing imagery to derive and spatially map the distribution of land surface temperatures and topographic attributes. Through comprehensive analysis, the research identifies the principal drivers of temperature variations and delineates their seasonal dynamics. The findings indicate that population density, night-time light intensity, land use, GDP (Gross Domestic Product), relief, and elevation exhibit positive correlations with land surface temperature, whereas slope demonstrates a negative correlation. Among natural factors, the correlations of slope, relief, and elevation with land surface temperature are comparatively weak, with determination coefficients (R²) consistently below 0.15. In contrast, socio-economic factors exert a more pronounced influence, ranked as follows: population density (R² = 0.4316) > GDP (R² = 0.2493) > night-time light intensity (R² = 0.1626). The overall hierarchy of the impact of individual factors on the temperature model, from strongest to weakest, is as follows: population, night-time light intensity, land use, GDP, slope, relief, and elevation. In examining Changchun and analogous cold-region cities within the northern temperate zone, the research underscores that socio-economic factors substantially outweigh natural determinants in shaping urban land surface temperatures. Notably, human activities catalyzed by population growth emerge as the most influential factor, profoundly reshaping the urban thermal landscape. These activities not only directly escalate anthropogenic heat emissions, but also alter land cover compositions, thereby undermining natural cooling mechanisms and exacerbating the urban heat island phenomenon. Full article

In recent years, China has experienced growing impacts from extreme weather events, emphasizing the importance of understanding regional atmospheric moisture dynamics, particularly Precipitable Water Vapor (PWV), to support sustainable environmental and urban planning. This study utilizes ten years (2013–2022) of Global Navigation Satellite System (GNSS) observations in typical cities in eastern China and proposes a comprehensive multiscale frequency-domain analysis framework that integrates the Fourier transform, Bayesian spectral estimation, and wavelet decomposition to extract the dominant PWV periodicities. Time-series analysis reveals an overall increasing trend in PWV across most regions, with notably declining trends in Beijing, Wuhan, and southern Taiwan, primarily attributed to groundwater depletion, rapid urban expansion, and ENSO-related anomalies, respectively. Frequency-domain results indicate distinct latitudinal and coastal–inland differences in the PWV periodicities. Inland stations (Beijing, Changchun, and Wuhan) display annual signals alongside weaker semi-annual components, while coastal stations (Shanghai, Kinmen County, Hong Kong, and Taiwan) mainly exhibit annual cycles. High-latitude stations show stronger seasonal and monthly fluctuations, mid-latitude stations present moderate-scale changes, and low-latitude regions display more diverse medium- and short-term fluctuations. In the short-term frequency domain, GNSS stations in most regions demonstrate significant PWV periodic variations over 0.5 days, 1 day, or both timescales, except for Changchun, where weak diurnal patterns are attributed to local topography and reduced solar radiation. Furthermore, ERA5-derived vertical temperature profiles are incorporated to reveal the thermodynamic mechanisms driving these variations, underscoring region-specific controls on surface evaporation and atmospheric moisture capacity. These findings offer novel insights into how human-induced environmental changes modulate the behavior of atmospheric water vapor. Full article

Drought impacts agricultural production and regional sustainable development. Accordingly, timely and accurate drought monitoring is essential for ensuring food security in rain-fed agricultural regions. Alternating drought and flood events frequently occur in the Heilongjiang River Basin, the largest grain-producing area in Far East Asia. However, spatiotemporal variability in drought is not well understood, in part owing to the limitations of the traditional Temperature Vegetation Dryness Index (TVDI). In this study, an Improved Temperature Vegetation Dryness Index (ITVDI) was developed by incorporating Digital Elevation Model data to correct land surface temperatures and introducing a constraint line method to replace the traditional linear regression for fitting dry–wet boundaries. Based on MODIS (Moderate-resolution Imaging Spectroradiometer) normalized vegetation index and land surface temperature products, the Heilongjiang River Basin, a cross-border basin between China, Mongolia, and Russia, exhibited pronounced spatiotemporal variability in drought conditions of the growing season from 2001 to 2023. Drought severity demonstrated clear geographical zonation, with a higher intensity in the western region and lower intensity in the eastern region. The Mongolian Plateau and grasslands were identified as drought hotspots. The Far East Asia forest belt was relatively humid, with an overall lower drought risk. The central region exhibited variation in drought characteristics. From the perspective of cross-national differences, the drought severity distribution in Northeast China and Inner Mongolia exhibits marked spatial heterogeneity. In Mongolia, regional drought levels exhibited a notable trend toward homogenization, with a higher proportion of extreme drought than in other areas. The overall drought risk in the Russian part of the basin was relatively low. A trend analysis indicated a general pattern of drought alleviation in western regions and intensification in eastern areas. Most regions showed relatively stable patterns, with few areas exhibiting significant changes, mainly surrounding cities such as Qiqihar, Daqing, Harbin, Changchun, and Amur Oblast. Regions with aggravation accounted for 52.29% of the total study area, while regions showing slight alleviation account for 35.58%. This study provides a scientific basis and data infrastructure for drought monitoring in transboundary watersheds and for ensuring agricultural production security. Full article

Although belowground litter decomposition critically influences lacustrine wetland soil carbon dynamics, the organ-specific microbial mechanisms driving soil organic carbon (SOC) accumulation remain unclear. Existing research has predominantly focused on aboveground litter, leaving a significant gap in the understanding of how roots and rhizomes differentially regulate carbon cycling through microbial community assembly and survival strategies. This study took Phragmites australis (a plant characteristic of lacustrine wetland) as the research object and examined how decomposing belowground litter from different organs affects microbial-mediated SOC accumulation through a one-year in situ field incubation in Jingyuetan National Forest Park, Changchun City, Jilin Province, China. Our findings reveal that root litter exhibited the highest decomposition rate, which was accelerated by intermittent flooding, reaching up to 1.86 times that of rhizome. This process enriched r-strategist microbial taxa, intensified homogeneous selection, and expanded niche width, directly promoting SOC accumulation. Rhizome litter decomposition enhanced dispersal limitation, promoted K-strategist microbial dominance, and indirectly modulated SOC through soil acidification. Mixed-litter treatments significantly enhanced SOC accumulation (up to three times higher than single-litter treatments) through synergistic nutrient release (non-additive effects < 0.04) and reinforced microbial network interactions. SOC accumulation varied significantly with the flooding regime as follows: non-flooded > intermittent flooding > permanent flooding. This study provides new insights into the microbially driven mechanisms of plant-organ-specific decomposition in the carbon cycling of wetland ecosystems. Full article

Innovative solutions are needed for urban flooding exacerbated by climate change. In light of this, this study developed an integrated framework for urban wetland flood control that combines Morphospatial Pattern Analysis (MSPA), minimum cumulative resistance (MCR) modeling, and complex network theory for optimizing an ecological network of flood control and mitigation wetlands in Changchun, China. The results show that the optimized ecological network significantly improved connectivity and flood mitigation efficiency. The node degree increased from 2.737 to 3.433, and the average clustering coefficient exhibited an increase from 0.074 to 0.231, enhancing material flow efficiency. Robustness analysis revealed that the optimized network’s connectivity robustness improved by 12.6%, 18.4%, and 24.1% under random, malicious, and controlled attack scenarios, respectively. Additionally, ecological corridors with a width of 30–50 m were identified as the optimal range for water conveyance potential, effectively dispersing peak runoff and reducing flood risk. This study provides both a transferable methodology for flood-resilient planning and specific policy actions, including priority conservation of high-betweenness nodes and restoration of fragmented wetlands, offering practical solutions for high-density cities facing similar climate challenges. Full article

The impact of reduced human activity on air quality in seven major Chinese cities was investigated by utilizing datasets of air pollutants and meteorological conditions from 2016 to 2021. A Generalized Additive Model (GAM) was developed to predict air quality during reduced-activity periods and rigorously validated against ground station measurements, achieving an R² of 0.85–0.93. Predictions were compared to the observed pollutant reductions (e.g., NO₂ declined by 34% in 2020 vs. 2019), confirming model reliability. Transfer learning further refined the accuracy, reducing RMSE by 32–44% across pollutants when benchmarked against real-world data. Notable NO₂ declines were observed in Beijing (42%), Changchun (38%), and Wuhan (36%), primarily due to decreased vehicular traffic and industrial activity. Despite occasional anomalies caused by localized events such as fireworks (Beijing, February 2020) and agricultural burning (Changchun, April 2020), our findings highlight the strong influence of human activity reductions on urban air quality. These results offer valuable insights for designing long-term pollution mitigation strategies and urban air quality policies. Full article

Tourism is a critical driver of economic growth, particularly in BRICS+ nations, where it contributes significantly to GDP and fosters multilateral cooperation. However, challenges such as limited direct air connectivity, regulatory barriers, and financial constraints hinder seamless travel experiences and impact tourism and trade. This study investigates the potential of direct air transport links among BRICS+ nations to alleviate these challenges, focusing on economic benefits, policy recommendations, and sustainability implications. Using a mixed-methods approach, including policy analysis and economic impact modeling, the findings reveal that enhanced air connectivity could reduce logistical inefficiencies, promote cultural exchange, and drive sustainable economic growth. This study concludes with strategies for implementing direct air routes and collaborative frameworks to advance the sustainable development goals of BRICS+ countries. Full article

Understanding the characteristics of urban plant multidimensional diversity and urban green spaces (UGSs) landscape patterns is the central theme of urban ecology, providing theoretical support for UGSs management and biodiversity conservation. Taking Changchun, a provincial city, as an example, a total of 240 plots were surveyed using the stratified random sampling method. We studied the effects of the urban park construction period on plant multidimensional diversities, landscape patterns of green spaces, and their associations in Changchun City, Northeast China. The results indicated that total woody species and tree species diversity attributes were both the highest in the construction period of 2001–2020 and lowest in the construction period before 1940. However, shrub species diversity attributes were completely the opposite. Diameter at the breast height (DBH) diversity index (H_d) was the highest in the construction period before 1940 and lowest in the construction period of 2001–2020. However, the height diversity index (H_h) showed the opposite trend. Phylogenetic structures of total woody species and tree species showed divergent patterns in parks constructed before 1940 and 1940–2000 period, while that in 2001–2020 period could not be determined. In contrast, the phylogenetic structure of the shrub species clustered across all construction periods. Landscape pattern metrics varied significantly among different construction periods. Total Area (TA) was the highest in the construction period of 2001–2020. The structural equation model (SEM) revealed that construction periods exerted significant direct effects on both multidimensional diversities and landscape patterns of green spaces. Specifically, construction periods indirectly affected tree species diversity through structural diversity and influenced shrub species’ phylogenetic diversity through shrub species diversity. What is more, Patch Density (PD), Edge Density (ED), and Aggregation Index (AI) correlated with H_h, which had a direct effect on the Shannon–Wiener diversity index of tree species (H′_t). Overall, the results indicated that species diversity can be enhanced through regulating landscape patterns, rationally selecting tree species, and optimizing plant configuration. These above results can provide scientific references for the configuration of plant communities and selection of tree species in urban parks, and offer important guidance for urban biodiversity conservation and enhancement. Full article

Mercury, a global pollutant with high biotoxicity, is widely distributed in soils, water bodies, and the atmosphere. Anthropogenic activities such as industrial emissions and coal combustion release large quantities of mercury into the environment, posing health risks to human populations. Strict implementation of the Minamata Convention and innovative remediation technologies can mitigate escalating environmental and public health risks. This study investigated the spatiotemporal dynamics of mercury in soils and atmosphere across four spatial scales (central city, county, township, and village) within the Changchun urban agglomeration, China. During spring, summer, and autumn of 2023, surface soil and atmospheric mercury concentrations (at 0 cm and 100 cm) were measured using LUMEX RA-915+ at 361 sites. Soil mercury exhibited seasonal variability, with a mean concentration of 46.2 µg/kg, showing peak values in spring and troughs in summer; concentrations decreased by 29.40% from spring to summer, followed by a 27.85% rebound in autumn. Spatially, soil mercury concentrations exhibited a core–periphery decreasing gradient (central city > county > township > village). Average concentrations at county, township, and village levels were 9.92%, 35.07%, and 42.11% lower, respectively, than those in the central city. Atmospheric mercury displayed seasonal variations; mean concentrations at 0 cm and 100 cm heights were 6.13 ng/m³ and 6.75 ng/m³, respectively, both peaking in summer. At 0 cm, summer concentrations increased by 35.61% compared to spring, then declined by 35.96% in autumn; at 100 cm, summer concentrations rose by 49.39% from spring and decreased by 31.08% in autumn. Atmospheric mercury at both heights decreased from the central city to the peripheries, with reductions of approximately 40% at 0 cm and 37–39% at 100 cm. Atmospheric mercury dynamics were significantly correlated with meteorological parameters such as temperature and humidity. Spatial autocorrelation analysis revealed scale-dependent clustering patterns: soil mercury Moran’s I ranked central city > county > village > township, while atmospheric mercury followed township > village > county > central city. Structural equation modeling demonstrated that different spatial scales had a significant negative effect on soil mercury concentrations, atmospheric mercury concentrations at 0 cm and 100 cm, and mercury and its compounds emissions. Organic matter content had a significant positive effect on soil mercury content. Temperature and humidity positively influenced near-surface atmospheric mercury. This multi-scale approach elucidates urban agglomeration mercury dynamics, highlighting core–periphery pollution gradients and seasonal patterns, thereby providing empirical evidence for regional mercury transport studies and providing a scientific foundation for future heavy metal management strategies. Full article

The urban heat island effect, triggered by global warming and rapid urbanization, has negatively impacted residents’ lives. It has been shown that urban green space (UGS) can improve the urban thermal environment. However, the stability and influencing factors of the urban green space cooling effect (UGSCE) in the context of climate change remain unclear. In this paper, we study the area within the Fifth Ring Road of Changchun City, using multi-source remote sensing image data to quantify and analyze the influencing factors of the cooling effect of urban green space and its stability on both regional and patch scales. The results show that on the regional scale, urban green spaces in Changchun have a strong cooling effect on the surrounding environment, which increases with the surface temperature (LST). However, there is a large fluctuation in the cooling effect. On the patch scale, the cooling effect of 35 green spaces showed a small increasing trend from 2013 to 2024. The cooling extent (CE) was more stable across temperatures relative to the cooling intensity (CI). Factors such as the green space area (A), perimeter (P), landscape shape index (LSI), and mean enhanced vegetation index (MEVI) had different degrees of influence on the cooling effect of green space and its stability. Green spaces with a high MEVI had a stronger cooling effect and stability. Based on this, planning suggestions such as increasing vegetation amount, maintaining green space area, optimizing green space morphology, and focusing on blue–green space are proposed to enhance the cooling effect of urban green space and its stability, which would improve the thermal environment of the city and enhance the comfort of residents. This study provides a reference basis for the scientific planning of urban green space and provides a scientific basis and practical guidance for the sustainable development of the city. Full article

In the face of the urgent need for the coordinated development of regional rural functions and the orderly and efficient integration of urban and rural areas, the problem of how to accurately identify the spatial correlation relationships and characteristics of rural elements among regions in Northeast China has become a key issue that urgently needs to be resolved. The results show the following: (1) The overall spatial correlation network (SCN) in the Northeast region from the perspective of rural element gravity has obvious differences. Each province has generated a strong connection center, and “strip-shaped” connection belts have been formed across provinces and cities. (2) From the perspective of the spatial pattern of the strong connection attributes of rural elements, Heilongjiang Province presents a polygonal “rhombus network”, Jilin Province presents a closed-loop “triangle network”, and Liaoning Province presents an irregular “trapezoid network”. (3) The connection relationships of rural element nodes within the provincial scope show that Yichun is an important hub connecting all directions within the province; Changchun and Siping have become the central nodes connecting the nodes on the northwest–southeast wings; Fuxin and Yingkou have become the central locations connecting the nodes on the southwest–northeast sides. (4) There are four sectors in the network, and the rural element transfer mechanism among the sectors shows that Block I and Block II are net spillover sectors, playing the role of “resource-based” sectors, and transmitting information to the net inflow Block IV through the broker Block III, presenting a “gradient” transmission mode. Full article

Heavy metal pollution in agricultural soils poses a serious threat to food security. Therefore, it is crucial to conduct risk assessments and issue early warnings about high levels of metal contamination for the sustained prosperity of agriculture. To assess the risks, identify the sources, quantify the amounts, and determine the extent of pollution from seven heavy metals, as well as to provide early warnings, 78 soil samples were collected from farmed lands in the Songnen Plain of Jilin Province. The average concentrations of Zn, Cu, Mn, Pb, Cd, Ni, and As were found to be 2.05, 1.5, 0.2, 1.09, 2.68, 1.53, and 1.17 times higher than the background values of Chinese soils, respectively. Source analysis indicated that toxic Pb originates from vehicle exhaust emission, while Cd, Cu, and Ni are attributed to industrial activities. Zn and As are likely associated with agricultural practices, and Mn predominantly stems from natural environmental sources. The geo-accumulation index suggests relatively high, accumulation levels for Zn, Cu, Mn, and Pb. Meanwhile, the single-factor pollution index indicates elevated pollution levels of Zn, Cu, and Cd. Potential ecological risk assessment reveals that certain areas within Changchun and Baicheng cities exhibit higher ecological risks. Notably, Cd has the highest potential ecological risk index (RI) of the seven heavy metals and warrants special attention. By analyzing annual pollutant accumulations, predictions can be made about the heavy metal content in four cities within the Songnen Plain, enabling the issuance of early warnings regarding soil heavy metal risks. The findings suggest that without proactive measures to mitigate heavy metal accumulation in soils, Changchun and Songyuan will reach severe pollution levels by 2031 and 2029, respectively. Full article

Cities in cold regions face significant challenges, including high carbon emissions, intense energy use, and outdated energy structures, making them critical areas for achieving carbon neutrality and sustainable development. While studies have explored the impact of spatial structures on urban carbon emissions, the effects of multi-scale spatial structures remain insufficiently understood, limiting effective spatial planning strategies. This research examines Changchun, a city in a severe cold region, using data from 2012 to 2021, including road networks, land use, nighttime light, and energy statistics. Employing spatial syntax, landscape pattern indices, random forests, and segmented linear regression, this research establishes a carbon emission translation pathway to analyze the nonlinear effects of multi-scale spatial structures. Findings reveal a 26.70% annual decrease in carbon emissions, with winter emissions 1.84 times higher than summer ones. High-emission zones have shifted from industrial areas to transportation, commercial, and residential zones, reflecting growing seasonal variability and structural changes. Spatial complexity increased while connectivity declined. Multi-scale analysis identified a “decrease–increase–decrease” pattern, with macro-scale centrality declining and micro-scale hierarchy rising. These results provide both theoretical and practical guidance for urban planning in cold regions, supporting early carbon neutrality and long-term sustainable development goals. Full article

Global urbanization has caused enormous challenges that seriously threaten ecological security and the food system. Thus, there is a need for finding an optimal solution for the eco-efficiency of cultivated land use (ECLU) that can promote the development of new-type urbanization, while ensuring the sustainable utilization of limited cultivated-land resources. The quantitative system of multi-scale ECLU used in existing studies is inadequate; it is necessary to establish a measurement system from the perspective of geographical spatial relationship that uses evaluation as a key basis for management. In this study, we considered the Changchun Metropolitan Area and a representative urban–rural transition area as the target regions and customized new ECLU evaluation systems for different scales. The super slack-based measure and gravity and social network analyses methods were applied to evaluate the ECLU and explore the structural characteristics of its spatial association network. The average ECLU value for the Changchun Metropolitan Area was 0.974; the results indicated that most of the study area was eco-efficient. The value of ECLU for the urban–rural transition area varied from 0.022 to 1.323; thus, the highly efficient cultivated land was mainly distributed around the urban built-up area. The spatial association network of ECLU revealed that the overall spatial correlations were relatively weak, with a significant “bipolar” division of ECLU; furthermore, the network hierarchy and stability needed improvement. Moreover, we noted distant attraction capacity and siphoning effects outside regional boundaries. In the Changchun Metropolitan Area, it manifested as a monocentric radiation, with Changchun City as the center. In the urban–rural transition area, the cultivated land in proximity to the newly built urban area was more likely to experience spatial spillover. These findings have important implications for strengthening land-use management and advancing sustainable agricultural development for new-type urbanization. Our study can be used by policymakers and stakeholders to design sustainable urban cities, while improving land-use management and optimizing resource use. Full article

Utilizing the best typhoon track data, district and county scale disaster data in Jilin Province, meteorological data, and geographical data, the combined weighting method of AHP-EWM (Analytic Hierarchy Process–Entropy Weight Method) and game theory is employed to conduct a comprehensive risk analysis and comparison of the disaster risk caused by two typhoons, Maysak and Haishen, in Jilin Province. Game theory enhances precision in evaluation beyond conventional approaches, effectively addressing the shortcomings of both subjective and objective weighting methods. Typhoon Maysak and Typhoon Haishen exhibit analogous tracks. They have successively exerted an impact on Jilin Province, and the phenomenon of overlapping rain areas is a crucial factor in triggering disasters. Typhoon Maysak features stronger wind force and greater hourly rainfall intensity, while Typhoon Haishen has a longer duration of rainfall. Additionally, Typhoon Maysak causes more severe disasters in Jilin Province. With regard to the four dimensions of disaster risk, the analysis of hazards reveals that the areas categorized as high risk and above in relation to the two typhoons are mainly located in the central-southern and eastern regions of Jilin Province. Typhoon Maysak has a slightly higher hazard level. During the exposure assessment, it was determined that the high-risk areas occupied 16% of the gross area of Jilin Province. It is mainly concentrated in three economically developed cities, as well as some large agricultural counties. In the context of vulnerability analysis, regions classified as high risk and above constitute 54% of the overall area. The areas classified as having high vulnerability are predominantly located in Yushu, Nong’an, and Songyuan. From the analysis of emergency response and recovery ability, Changchun has strong typhoon disaster prevention and reduction ability. This is proportional to the local level of economic development. The mountainous areas in the east and the regions to the west are comparatively weak. Finally, the comprehensive typhoon disaster risk zoning indicates that the zoning of the two typhoons is relatively comparable. When it comes to high-risk and above areas, Typhoon Maysak accounts for 38% of the total area, while Typhoon Haishen occupies 47%. The regions with low risk are predominantly found in Changchun, across the majority of Baicheng, and at the intersection of Baishan and Jilin. Upon comparing the disasters induced by two typhoons in Jilin Province, it was observed that the disasters caused by Typhoon Maysak were considerably more severe than those caused by Typhoon Haishen. This finding aligns with the intense wind and heavy rainfall brought by Typhoon Maysak. Full article