Assessing Soil Carbon Sequestration Potential in Urban Green Spaces

Thesis Abstract

Urban green spaces are increasingly recognized as vital components in mitigating climate change through their capacity to sequester atmospheric carbon in soils. However, the potential of different types of urban green cover—such as parks, green roofs, community gardens, and street trees—to function as significant carbon sinks remains inadequately quantified and understood within a comprehensive framework. This study aims to assess the soil carbon sequestration potential in urban green spaces through systematic field measurement and analysis, thereby providing empirical evidence to inform urban planning and environmental management policies. The specific objectives include determining the soil organic carbon (SOC) stocks across different urban green space typologies, evaluating the influence of vegetation cover, soil properties, and management practices on SOC accumulation, and developing predictive models to estimate sequestration potential at varying spatial scales. The study employs a mixed-methods research design combining quantitative soil sampling with qualitative assessment of land management practices. The targeted population encompasses urban green spaces within the city of Metropolitanopolis, with a sample size of 120 plots selected through stratified random sampling to ensure representation across diverse green space types, land use histories, and geographic locations. Soil samples were collected at depths of 0–15 cm and 15–30 cm using a soil corer, with a minimum of three samples per plot, resulting in a total of 360 samples. Laboratory analysis included dry combustion using a LECO CNS analyzer to determine SOC concentrations, complemented by measurements of soil texture, pH, bulk density, and moisture content to elucidate factors influencing carbon dynamics. Data reliability was ensured through calibration of instruments and replication of a subset of samples. Data analysis involved descriptive statistical techniques to summarize SOC stocks across green space types, followed by inferential statistics including analysis of variance (ANOVA) and multiple regression analysis to identify significant predictors of soil carbon sequestration. Geospatial modeling using Geographic Information Systems (GIS) facilitated the spatial extrapolation of findings, while regression analysis informed the development of predictive models for estimating SOC stock potentials in unexamined areas. The theoretical framework integrates the Biogeochemical Theory of Soil Carbon Dynamics and the Urban Ecosystem Theory, with the latter explaining interactions between urban land use, vegetation, and soil processes influencing carbon sequestration. Expected findings indicate that soils in green spaces with dense, native vegetation, minimal soil disturbance, and organic-rich management practices exhibit significantly higher SOC stocks compared to disturbed areas or those with invasive species. Variations across green space typologies are anticipated, with parks and community gardens showing greater sequestration potential relative to street trees and green roofs, owing to differences in soil depth, management, and plant cover. The study also expects to identify key soil and management factors that significantly influence SOC levels, such as soil texture, pH, and organic matter inputs. This research contributes to the existing body of knowledge by providing robust quantitative data on soil carbon sequestration in urban environments, addressing gaps related to spatial variability and management effects. It advances the understanding of urban soils as active carbon sinks and develops models that can be integrated into urban climate mitigation strategies. The findings offer practical recommendations for optimizing green space management to maximize soil carbon storage, including promoting native vegetation, minimizing soil disturbance, and adopting organic land management practices. Policy implications include the validation of urban green spaces as credible components of climate action plans and the formulation of guidelines for their sustainable management to enhance their carbon sequestration capacity. In conclusion, the study affirms that urban green spaces possess significant yet underutilized potential for carbon sequestration. It underscores the importance of targeted management strategies to enhance this capacity and advocates for integrating soil carbon considerations into urban planning frameworks. Future research directions include longitudinal assessments of SOC dynamics and exploring microbial processes influencing soil carbon stability, further strengthening urban climate resilience initiatives.