Impact of Urbanization on Soil Microbial Diversity and Functionality

Thesis Abstract

Urbanization significantly alters soil environments, leading to changes in microbial communities that are critical for maintaining soil health and ecosystem functions. However, detailed empirical data on how increasing urban land use impacts soil microbial diversity and functionality remain limited. This study aims to evaluate the effects of urbanization on soil microbial communities, focusing on their diversity, functional potential, and enzyme activities across different land-use types within the metropolitan region. The specific objectives are to quantify microbial diversity indices, assess functional gene abundance, and analyze enzyme activity levels in soils from urban, peri-urban, and rural areas. The research adopts a comparative cross-sectional design, collecting soil samples from fifteen sites—five from each land-use category—representing various degrees of urban development. A total of 150 soil samples (10 per site) will be analyzed. Standardized soil sampling methods will be employed, with samples subjected to DNA extraction followed by high-throughput sequencing techniques such as Illumina MiSeq to characterize microbial taxonomic diversity. Quantitative PCR (qPCR) will be used to quantify key functional genes associated with nutrient cycling, including nitrogen fixation, nitrification, and carbon degradation. Enzyme activities related to these processes, such as urease, dehydrogenase, and phosphatase assays, will be measured using spectrophotometric methods. The data analysis will include descriptive statistics, ANOVA to compare microbial diversity and functional parameters across land-use types, and regression analysis to explore relationships between urbanization intensity and microbial metrics. Additionally, multivariate statistical techniques like redundancy analysis (RDA) will be used to relate microbial community composition to soil physicochemical properties. The theoretical framework integrates the Soil Microbial Community Theory and the Urban Ecology Theory, underscoring how urban stressors influence microbial diversity and ecosystem functions. It is hypothesized that urban soils will exhibit reduced microbial diversity and altered functional gene profiles compared to rural soils, accompanied by lower enzyme activities indicative of suppressed microbial processes. Expected findings suggest significant declines in microbial diversity indices and functional gene abundance with increasing urbanization, along with shifts in community composition favoring urban-adapted microbial taxa. These alterations may impair critical soil functions such as nutrient cycling, with implications for urban sustainability and green infrastructure. The study is expected to contribute novel empirical evidence on how anthropogenic land use changes modify soil microbial ecosystems, filling a gap in the understanding of urban soil microbiology in developing metropolitan contexts. Its findings will inform urban planning and soil management practices aimed at conserving microbial biodiversity and ecosystem services essential for resilient urban environments. The main conclusion will emphasize the detrimental impacts of urbanization on soil microbial health and advocate for integrated land-use strategies that promote microbial diversity. Recommendations will include incorporating microbial-friendly practices in urban development, such as in situ soil restoration and green infrastructure planning, and further research to explore long-term dynamics of microbial resilience to urban stressors. Overall, this research aims to advance ecological theory in urban soils and support policy development for sustainable urban landscapes through a microbiological lens.