Urban Ecosystems Research Articles

Surplus or deficit? Quantification of carbon sources and sinks and analysis of driving mechanisms of typical oasis urban agglomeration ecosystems

The relationship between carbon sources and sinks, along with their balance, is a crucial indicator for assessing ecosystem health. Ecosystem protection mitigates climate change and promotes the carbon cycle balance. Consequently, to effectively assess the status of carbon sources and sinks in an oasis ecosystem, this study utilized remote sensing and statistical data to estimate the natural carbon sources and sinks, energy carbon emissions(ECE), and carbon surpluses or deficits in the urban agglomeration of the northern slopes of the Tianshan Mountains(UANSTM) for a period 2000–2022 from a perspective of the natural-social-economic system. The driving mechanisms were analyzed using the optimal geodetector model (OPGD) and generalized divisia index method (GDIM). The results show(1) throughout the study period, natural carbon sources and sinks in the UANSTM exhibited a distribution pattern that diminished from the Tianshan Mountains axis northward and southward, accompanied by a fluctuating increase over time. ECE predominantly occurred in urban built-up areas and adjacent cultivated lands, totaling an increase of 88.48 × 104 TgC. (2) The change trend showed an overall predominance of carbon sources, with the rate of increase of carbon sources being greater than that of carbon sinks. Grassland-cultivated land and construction land interaction area exhibited significant changes in carbon sources and sinks. (3) During the study period, the UANSTM experienced a consistent carbon deficit, averaging −68.11 TgC annually. Spatially, this deficit evolved from discrete points to linear and then to areal patterns. (4) Precipitation and elevation were the primary determinants of natural carbon sources and sinks. Whereas GDP with a contribution of 50.4%,was the predominant driver of ECE across each prefecture-level city. Development of policies that synergize regional natural and socioeconomic systems is an important means of achieving a carbon balance. The results of this study provide a reference for adding a research paradigm on carbon sources and sinks in oasis urban agglomerations and for low-carbon development.

Evaluating the role of recalcitrant dissolved organic matter in bacterial community dynamics in urbanized freshwater ecosystems

Dissolved organic matter (DOM) and recalcitrant dissolved organic matter (RDOM) play distinct roles in shaping microbial communities. However, characterizing these roles is difficult, especially in ecosystems subjected to varying degrees of anthropogenic influence. This study investigated the molecular compositions and ecological impacts of DOM and RDOM in the Fen River, Shanxi Taiyuan, comparing pristine upstream regions with highly urbanized downstream areas. Using 16S rRNA gene sequencing and LC-MS-based metabolomics, we observed significant shifts in microbial community composition, diversity, and metabolic functions. Upstream communities, characterized by higher diversity, were dominated by Bacteroidota, Proteobacteria, and Cyanobacteria, while downstream communities, influenced by pollution, exhibited increased expression of genes related to amino acid metabolism. Fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that upstream DOM contained higher proportions of complex, high molecular weight compounds, including significant proportions of carboxyl-rich alicyclic molecules (CRAM) and island of stability (IOS) compounds, which play key roles in long-term carbon storage and microbial carbon sequestration. In contrast, downstream DOM was characterized as having lower aromaticity and more saturated compounds, with reduced proportions of CRAM and IOS, reflecting the impact of anthropogenic activities. These findings underscored the critical roles of CRAM and IOS in regulating DOM stability and microbial communities, further highlighting the need for targeted pollution control strategies to preserve ecosystem function in urbanized water bodies.

Trophic activity of pedofauna in two gardens of Saint-Petersburg (experience of using the express bait-lamina test methid)

The plant and soil cover of cities functions as their ecological framework. Soil invertebrates play an important role in urban ecosystems. Trophic activity of pedofauna is an integral indicator of its condition. The trophic activity of macroand mesopedofauna in the soils of the gardens of the Russian Museum (St. Petersburg) was determined by the express method baitlamina test. The average values of the degree of consumption of bait by pedobionts amounted to 10.9 ± 1.6% for the Summer Garden and 8.5 ± 3.5% for the Mikhailovsky Garden. The variability of trophic activity indices between different sample areas was established – in the Summer Garden it varies from 2 ± 6.2% to 21.8 ± 8.4%, and in the Mikhailovsky Garden – from 2.8 ± 4.5% to 19.3 ± 8.8%. Differences in trophic activity within the vegetation season were noted. The lowest degree of bait consumption (less than 2%) was observed in the driest and hottest months in the middle of the vegetation period, and the highest (within 19–22%) – at the beginning and end of the vegetation period under the most favorable hydrothermal conditions.

Variation in flower morphology associated with higher bee diversity in urban green spaces.

Urbanization is a leading threat to biodiversity, but scientifically informed management of urban ecosystems can mitigate negative impacts. For wild bees, which are declining worldwide, careful consideration of flower choice in public and private green spaces could help preserve their diversity. While floral density and species richness are both linked to wild bee diversity, the mechanisms underlying these relationships are not fully understood. Here, we tested two hypotheses relating the influence of floral trait composition to bee species richness, which we have termed the within-trait diversity and optimal floral trait hypotheses. Specifically, we assessed whether variation in bee richness relates to variation in the weighted variance (trait diversity) and mean (optimal trait) of floral traits observed in urban green spaces across the city of Montreal, Canada. Our analyses focused on two floral traits relating to pollinator feeding success: nectar sugar concentration and corolla length. After accounting for variation in floral density among sites, bee richness was positively related to community-weighted variance in corolla length, supporting the within-trait diversity hypothesis. These findings suggest that management practices that increase the diversity of flower morphologies in urban green spaces can promote the persistence of wild bee communities in cities.

Beyond Composting Basics: A Sustainable Development Goals—Oriented Strategic Guidance to IoT Integration for Composting in Modern Urban Ecosystems

IoT-based composting provides clear advantages over conventional urban composting in areas such as enhanced monitoring, efficiency, resource utilization, and management. Bibliometric analysis of 121 publications on IoT-based urban composting identified critical research gaps and emphasizes the necessity for a strategic framework for full implementation and execution of sustainable development goals-oriented IoT-based composting in modern cities across. Under the key theme of IoT-based urbanized composting automation, 16.5% of publications focus on urbanized composting automation but overlook the system’s scalability. The lowest mean citations of 72.7 (22.3% of publications) in intelligent composting process optimization show the lack of broader applications. A total of 28.9% of total publications focus on urban composting sustainability assessment but lack IoT integration in their scope. The composting process, pollution, environmental impact, cost, and life cycle analysis of modern city composting share 19% and 13.3%, respectively. However, both key themes lack real-time monitoring, operation, and economic feasibility for scalable models. The article highlights a fragmented landscape providing sustainable development goals-oriented strategic guidance for the full implementation and execution of IoT-based composting facilities in modern city ecosystems. The article comprehensively explains the budgetary constraints, scalability, data management, technological compatibility, privacy, security, and regulatory compliance essential for sustainable operation.

Advancing Sustainability in Urban Planning by Measuring and Matching the Supply and Demand of Urban Green Space Ecosystem Services

As global cities rapidly develop, the realization of sustainable urban development has become a pressing global concern. As a critical component of the urban built environment, urban green spaces are essential for maintaining the sustainability of urban ecosystems by offering a variety of ecological benefits. However, there are some problems in the design and construction of urban green framework, which often disregard the real needs of residents and hinder the sustainable development of urban areas. Therefore, urban planning that takes into account the supply and demand relationship of urban green space is considered to be a key technology that should help to improve residents’ happiness and promote urban sustainable development. This paper takes Zunyi City as an example; selects six indicators; combines UAV images, population, economic, and environmental data to evaluate ecosystem services valuation existing green space in the city; and analyzes its social and ecological needs. Affected by land utilization and development density, the supply value showed low spatial density characteristics in the central urban area and high spatial distribution characteristics in the surrounding urban area. The correlation between demand value and population density is the largest, and the distribution pattern is similar to that of population density. The supply-demand ratio in the study area is −0.54, indicating a severe imbalance between supply and demand. The correlation analysis between the comprehensive supply and demand ratio and each influencing factor shows that the correlation with population density is the largest. The combination of supply and demand maps addresses a major problem in planning, namely, ensuring that communities have priority in providing urban green space based on society’s need for ecosystem services. In addition, these maps will help develop the best green space planting plans to meet the specific needs of different communities. Taken together, the findings can help city planners and decision makers improve the layout of urban green areas, increase ecosystem service potential, and improve urban environmental quality and sustainability.

The spatiotemporal distribution patterns and impact factors of bird species richness: A case study of urban built-up areas in Beijing, China

This study aims to investigate the distribution patterns of bird species in urban built-up areas and their impact factors from multiple dimensions, including spatiotemporal distribution, environmental changes, and anthropogenic disturbances, as well as overall distribution and local hotspots. Leveraging geographic distribution data of 383 bird species from 70 families and 21 orders, the study recorded dynamic changes in bird distribution within urban built-up areas characterized by highly heterogeneous core areas and suburban areas. It examined species distribution across different seasons and land cover types, evaluated population fluctuations based on migratory behaviors, and assessed the relative abundance of bird families and species in hotspot areas. Additionally, this study employed three tree-based machine learning algorithms—Decision Tree (DT), Random Forest (RF), and Extreme Gradient Boosting (XGBoost)—to investigate the influence of environmental factors on bird species distribution within urban built-up areas. The findings showed that, temporally, the number of observed bird species in the study area peaked in May and September, while the lowest numbers of species (54.83 %) and individuals (5.45 %) were recorded during the high-temperature period from June to August. Spatially, (1) woodlands, including stable mature forests, unstable juvenile forests, and sparse vegetation, recorded the highest frequencies of bird observations (2,053 times), bird species (369 species), and bird individuals (38,623 individuals); (2) comprehensive parks, where bird species demonstrated higher adaptability to anthropogenic disturbances, experienced a more significant decline in species richness compared to country parks; and (3) the number of bird species in hotspot areas located in the core areas, which developed earlier, has decreased annually, while the number of species in suburban areas, which developed later, has increased annually. In terms of impact factors, water area (WA), point of interest kernel density (DPOI), relative humidity (RH), green space area (GSA), and nighttime light pollution (NL) were identified as the five most important environmental factors affecting bird species richness. These results suggest that although birds exhibit some adaptability to environmental changes and anthropogenic disturbances, species distribution remains significantly impacted. This research aims to provide a planning framework for future urban development that promotes biodiversity and adaptability, thereby bolstering the resilience of urban ecosystems.

Urban ecosystem services research in Russia: Systematic review on the state of the art.

Research on urban ecosystem services (ES) covers many regions globally, yet significant gaps remain in several areas, including Russia. Furthermore, the number of publications on Russian ES is still very low, and most of them focus on ES assessment on the national level which results in an incomplete understanding of ES provision in Russiancities. To fill this gap, 197 publications on urban EShave been systematically reviewed. Thosemostly included researchon urban ESin Russia as well as in other cities of the world that represented case studies within international collaborations of Russian scientists with other partners. The paper presents the main aspects of the ES concept adoption and operationalizing in the Russian scientific discourse, by providing an overview of the current research on the relationships between humans and urban ecosystems. Spatially, the majority of studies focused on large cities;herewith field surveys, statistical analysis, expert evaluations, and mappingwere oftenused as the main research methods. Four key challenge areas have been revealed: anthropogenic pressure on soils and vegetation, urban green spaces (UGS) and their quantity and quality for ES provision, thevalue of ES assessment for urban planning, and payments for ES. To address these challenges, future research should focus on the role of urban ES for cityresilience and sustainability, ecosystem disservices, rural-urban interactions, broader testing and validation of ES mapping and assessment as well as better integration of ES in economic, regulatory and compensation mechanisms.

Relationship between negative air ions and environmental factors in the urban forest parks of Yangzhou in urban and suburban areas

Negative air ions (NAIs) play an important role in human well-being, serving as key indicators of air cleanliness and contributing to both psychological and physiological health. This study aims to investigate the factors influencing NAI concentration in urban and suburban forest parks, enhancing our understanding of the correlation between NAIs and environmental factors. Songjiacheng Urban Forest Park and Runyang Wetland Suburban Forest Park in Yangzhou City were selected as the subjects of this research, and continuous measurements of NAI concentration were conducted over a three-year period. Additionally, seven meteorological factors were monitored. A random forest model was employed to analyze and compare the data from the two forest parks, identifying the environmental factors with significant impacts on NAI concentration. The results indicate that in Songjiacheng Urban Forest Park, NAIs exhibited significant sensitivity to temperature, followed by atmospheric pressure. Conversely, in Runyang Wetland Suburban Forest Park, PM2.5 (particulate matter 2.5) exerted the greatest impact on NAIs, followed by humidity. We conducted a thorough analysis of data to explore the intricate connections between negative air ions and a variety of environmental factors within two urban forest parks. Our findings have significantly broadened our perspective on the characteristics of Negative Air Ions (NAIs) and their management implications within these urban green spaces. This enhanced understanding is pivotal for developing more effective strategies for environmental stewardship and the preservation of these vital urban ecosystems.

Valuing the spatial structure and influencing factors of urban innovation from the perspective of social networks

ABSTRACT Valuing the spatial structural characteristics and evolution mechanisms of urban innovation networks (UIN) is crucial for promoting regional innovation development. This study constructs the UIN for the Yangtze River Economic Belt (YREB) and examines its spatial structural characteristics and driving factors from a social network perspective. The results indicate that: First, the network relationships within the urban innovation ecosystem in YREB continue to expand, enhancing stability, synergy and connectivity. Second, interaction relationships dominate the network, establishing distinct block functions, with provincial capitals serving as core nodes. Third, YREB can be divided into four blocks: the main inflow block, the main outflow block, the bidirectional spider block and the agent block, each exhibiting unique roles within the network. Fourth, increasing network density and connectedness while reducing hierarchy and enhancing efficiency positively impacts urban innovation. Strengthening node centrality characteristics is beneficial for promoting urban innovation. Lastly, proximity is conducive to the formation of UIN. Digital technology and traffic integration are replacing geographical and institutional factors, becoming key elements in the formation of UIN. Therefore, we propose optimising the spatial structure of UIN and shifting the driving paradigm from geographic and institution proximity to the digital technology and traffic proximity.

Integrated assessment of urban green infrastructure multifunctionality: Insights from Stavanger

Optimised contributions of green infrastructure (GI) to urban ecosystem services are strongly related to its multifunctionality. The challenge, however, is that the concept of multifunctionality still needs to be transformed into an operationalised assessment to evaluate current performance, which is instrumental in supporting spatial planning and policy strategies. Using the case of Stavanger City (Norway), the study conducted a spatial assessment of the multifunctionality of the urban green infrastructure. The study used a comprehensive set of 27 function indicators estimated for each of the 156 spatial units classified by their type, age, size, and biophysical characteristics. Correlation patterns among indicators and how the average and effective multifunctionality related to unit characteristics were analysed using correlation and multivariate approaches.The study demonstrated weak correlations between function indicators but revealed some potential trade-offs and function bundles. Notably, bundles related to tree cover (e.g. C sequestration, stormwater retention) had negative relationships with facilitation measures. There was a large overlap in functions between GI types associated with public green spaces and parks. Moreover, the characteristics of green infrastructure units, like size and age, primarily affected multifunctionality through effects on function indicators. Regarding the city-wide multifunctionality, we found some turnover and subsetting of functions among units, supporting multifunctionality at larger spatial scales. However, the average contributions from different GI types were similar. The study highlights the need to understand correlation patterns among function indicators and function bundles as critical to benefit from synergies and avoid unintentional trade-offs when designing and managing urban green areas.

Construction and optimization of ecological corridors in coastal cities based on the perspective of “structure-function”

The contradiction between the demand of urban economic development and ecological environmental protection is becoming more and more prominent, and the reasonable construction of ecological corridors is of great significance for the protection of urban ecosystems. Taking Changle District of Fuzhou coastal city as an example, this study proposes an ecological source identification method from the perspective of “structure-function” by combining Morphological Spatial Pattern Analysis (MSPA) and Remote Sensing Ecological Index (RSEI) methods, and constructs and optimizes ecological corridors by means of the model of Minimum Cumulative Resistance (MCR) and Circuit Theory. The results show that: (1) a total of 20 ecological sources were extracted based on MSPA-RSEI; (2) a total of 31 ecological corridors were extracted based on Linkage Mapper, including 8 Level 1 corridors, 13 Level 2 corridors, and 10 Level 3 corridors; (3) the Pinch Point and Barrier Mapper software was utilized to identify 6.01 km2 and 2.59 km2, respectively, as Level 1 “pinch points” and barrier points within the study area. The land use types of these areas were as follows: The majority of “pinch points” were forested (60.72%), while the majority of barrier points were composed of construction land (55.27%), bare land (17.27%), and cultivated land (13.90%). (4) the optimal width of the corridor was determined by using the buffer zone method and gradient analysis: 30 m for the Level 1 corridor, 60 m for the Level 2 and Level 3 corridors, and the average current density before and after the construction of the eco-corridor was increased from 0.1881 to 0.4992. The results of the study can provide a reference for the decision-making of the ecological construction of the Changle District and the coastal urban areas of eastern China.

Drought in south-west Australia links to urban immigration across multiple avian taxa

Background Urban areas are a significant and rapidly expanding part of the global landscape. Urban expansion occurs alongside climate change, with both linked to declines in native species. However, urban environments can offer alternative resources during extreme climatic events such as droughts. Aims We sought to identify bird species that had an increased presence in the major urban center of south-west Western Australia during a climate anomaly characterized by record low rainfall and high temperatures. Methods Using eBird data, we analyzed changes in the reporting rates of all bird species in the period from January 2019 to August 2024. Generalized linear models were used to assess the influence of cumulative 6-month, 12-month, and 18-month rainfall on species reporting rates. Key results Reporting rates increased dramatically (up to nine times higher than average) around the time of the drought, before reducing back to the average once the drought was broken for four species: (1) the black-shouldered kite; (2) the black-tailed native-hen; (3) the tawny-crowned honeyeater; and (4) the western spinebill. Cumulative 6-month rainfall was a strong predictor for the raptor and the two honeyeaters. Other similar species showed no significant change in reporting rate, suggesting the effect is highly species dependent. Conclusions Multiple different types of birds may utilize urban areas during drought events. Further research is needed to identify what drives movement of wildlife in response to such events, and the type of urban resources the birds are using. Implications Urban ecosystems should be integrated into broader conservation plans to support species through the interacting challenges posed by climate change and urbanization.

Assessment and Dynamic Prediction of Green Space Ecological Service Value in Guangzhou City, China

As an important part of the urban ecosystem, urban green space provides a variety of ecosystem services, including climate regulation, soil conservation, carbon sink and oxygen release, and biodiversity protection. However, existing remote sensing evaluation methods for ecological service value lack the evaluation indicators of ecosystem service value for Guangzhou, China, and the evaluation method depends on the land cover type. Based on remote sensing technology and random forest algorithm, this study addresses these gaps by integrating remote sensing technology with a random forest algorithm to enhance the accuracy and rationality of ESV assessments. Focusing on Guangzhou, China, we improved the ecological service value evaluation system and conducted dynamic predictions based on land-use change scenarios. Our results indicate that the total ESV of Guangzhou’s green space was USD 7.323 billion in 2020, with a projected decline to USD 6.496 billion by 2030, representing a 12.37% reduction due to urbanization-driven land-use changes. This research highlights the noticeable role of green spaces in urban sustainability and provides robust, data-driven insights for policymakers to design more effective green space protection and management strategies. The improved assessment framework offers a novel approach for accurately quantifying urban ecosystem services and predicting future trends.

Similarities and Dichotomies Between Nature-Based Solutions and Green Infrastructure: a Systematic Literature Review

Objective: The study seeks to address the following question: What are the similarities and dichotomies between green infrastructure (GI) and nature-based solutions (NBS) from the perspective of Brazilian researchers, and how do the identified solutions mitigate the depletion of urban ecosystem services? Method: A Systematic Literature Review (SLR) was conducted using the PRISMA protocol in research within the CAPES Journal database. The inclusion and exclusion criteria were original texts, peer-reviewed, published in national and international journals in Portuguese, covering the themes of NBS, GI, informal settlements, and public open space. After reviewing the 90 identified texts, a final selection of 41 texts was made for the SLR. Originality/Value: These texts were analyzed from a novel perspective, bringing together the themes of GI, NBS, ecosystem services protection, and urban land use. Results and Discussion: The study identified the authors’ views on the pressures of urbanization on ecosystem services and the solutions for their protection. It was concluded that the concepts of NBS and GI are often conflated in most approaches and that adopting urbanization associated with nature faces conceptual, operational, and managerial challenges. Research Implications: The research provides insights into the integration of GI and NBS in urban planning to address the challenges of uncontrolled urbanization and the degradation of ecosystem services.

Capturing drought stress signals: The potential of dendrometers for monitoring tree water status.

The severity of droughts is expected to increase with climate change, leading to more frequent tree mortality and a decline in forest ecosystem services. Consequently, there is an urgent need for monitoring networks to provide early warnings of drought impacts on forests. Dendrometers capturing stem diameter variations may offer a simple and relatively low-cost opportunity. However, the links between stem shrinkage, a direct expression of tree water deficit (TWD), and hydraulic stress are not well understood thus far. In this study, we exposed two widespread conifers Pinus sylvestris and Larix decidua to lethal dehydration by withholding water and closely monitored TWD, midday water potential ($\psi $), and midday stomatal conductance ($g_{s}$) under controlled greenhouse conditions. We found strong relationships between the three variables throughout the dehydration process, particularly suggesting the potential for continuous $\psi $ predictions and stomatal closure assessments. However, the relationships decoupled during recovery from severe drought. We also identified TWD thresholds that signal the onset of drought stress and tissue damage, providing insights into stress impacts and recovery potential. While these findings are promising, challenges remain in practically transferring them to field set-ups by suitable TWD normalization. Importantly, we observed that midday $g_{s}$ was drastically reduced when TWD persisted overnight, providing a directly applicable drought stress signal that does not require normalization. In conclusion, while challenges remain, our results highlight the potential of dendrometers for monitoring tree water dynamics. Implementing dendrometer networks could support the development of early-warning metrics for drought impacts, enabling large-scale monitoring in diverse settings, such as urban areas and forest ecosystems.

Spatiotemporal variations in land surface temperature within an urban ecosystem: A comprehensive assessment of land cover change in Düzce, Türkiye

Spatiotemporal variations in land surface temperature within an urban ecosystem: A comprehensive assessment of land cover change in Düzce, Türkiye

Urbanization and plant diversity in urban fringes: Differential responses across life forms

Urban fringe areas, as critical transition zones between urban expansion and natural environments, provide essential ecosystem services that enhance the overall health and sustainability of urban environments. However, previous studies have focused on urban built–up areas while neglecting the unique conditions of urban fringe zones. This study investigated the spatial distribution patterns of plant diversity across different life forms in Jiangdong New District and their responses to urbanization levels. The results indicate that hot and cold spots of diversity for trees and shrubs show similarity, while diversity in herbaceous plants differs significantly. Nighttime light intensity, POI (Point–of–Interest) density, and road density are primary influencing factors, with nighttime light intensity and POI density having the greatest combined impact, and herbs showing the highest sensitivity to these factors. Further analysis reveals that in the northwestern forest, grassland, and farmland mosaic areas, urbanization levels are positively correlated with tree and shrub diversity but negatively correlated with herb diversity. In the southeastern nursery planting area, urbanization levels consistently relate to the diversity of these three plant types. These findings underscore the necessity of adopting diverse conservation and management strategies in urban fringe areas to address the ecological needs and functional contributions of different plant types. This provides new perspectives on urban planning and ecological conservation that can help improve the overall health and sustainability of urban ecosystems.

The dual role of coastal mangroves: Sinks and sources of microplastics in rapidly urbanizing areas

Mangrove ecosystems are vital for coastal protection, biodiversity, and pollution interception, yet their interactions with microplastics in rapidly urbanizing regions remain underexplored. This study investigated the microplastic dynamics in the Maozhou River and Dasha River, along with the coastal Xiwan Mangrove Park in the Pearl River Estuary, the second largest estuary in China. Samples were collected from mangrove and surrounding areas, identifying microplastics using Fourier-transform infrared spectroscopy (FTIR) and Laser Direct Infrared (LDIR) techniques. Microplastic concentrations ranged from 245.8 to 1562.4 n/m³ in water and 374.3 to 7475.3 n/kg in sediments. The Maozhou River exhibited consistent microplastic levels across varying hydrological conditions, while the Dasha River and Xiwan Mangrove showed greater sensitivity to water flow changes influenced by urban land use. During high-flow periods, urban river microplastic concentrations decreased due to dilution, whereas mangrove areas experienced elevated levels in water from urban runoff, upstream retention, and sediment resuspension, suggesting a potential for outward release. Weaker water dynamics led to increased microplastic accumulation in mangrove sediments. The distribution of microplastic types was influenced by multiple urban pollution sources, with synthetic rubbers linked to urban transportation comprising over 50 % of some samples, peaking at 79 %. These findings underscore the dual role of mangroves as microplastic sinks and potential sources, highlighting the significant impact of hydrological conditions on their function. This study offers new insights into microplastic pollution in urban mangrove ecosystems and emphasizes the urgent need for improved management strategies in coastal areas facing rapid urbanization.

Characterization of organic materials in regulating soil carbon sequestration of urban greenspaces: Links to microbial necromass and community composition

Application of organic material is a win-win strategy that effectively boosts soil carbon (C) storage and promotes organic waste recycling in urban ecosystems. However, the divergent responses of C sequestration to organic materials and the underlying mechanisms remain unclear. Using molecular and litterbag methods, this study examined soil organic C (SOC) content, C sequestration efficiency of organic material (CSE-organic material), microbial necromass and community composition in urban greenspaces amended with different types of organic materials. The field experiment had seven treatments: addition of green waste (GreenWaste), green waste compost (GreenWasteCompost), biogas residue (BiogasResidue), biogas residue compost (BiogasResidueCompost), peat (PEAT), biochar (BioChar), and no organic material (Control). Organic materials after 16 months application increased SOC content by 34.1–87.0% compared with the Control and presented CSE-organic material in the order: BioChar > GreenWasteCompost > PEAT > BiogasResidueCompost > GreenWaste > BiogasResidue. Aromaticity index was positively correlated with CSE-organic material, indicating that aromatic C addition had a strong capacity to enhance C sequestration. Microbial necromass increased from 2.7 g C kg−1 in the Control to 3.9–5.0 g C kg−1 under organic materials addition. Bacterial necromass was enriched in the BiogasResidue and BiogasResidueCompost treatments, primarily because of sufficient substrate that facilitated the proliferation and activity of copiotrophic Firmicutes, whereas fungal necromass was 8.8–19.1% higher in the GreenWaste, GreenWasteCompost, and PEAT treatments than that in the BiogasResidue and BiogasResidueCompost treatments, accompanying by an increasing abundance of Ascomycota. However, the contribution of microbial necromass to the increased SOC was negatively correlated with CSE-organic material, suggesting that the input of recalcitrant C weakened the role of microbial necromass in C retention. Overall, this study reveals that the efficiency of organic materials application in promoting soil C accumulation depends largely on recalcitrant C rather than microbial necromass, which highlights the important role of organic waste acting as a C source in achieving urban sustainable development.