Urban forest plant diversity affects soil organic carbon by regulating functional genes in Nanning

Urban forests serve as reservoirs of soil organic carbon (SOC) within ecosystems and play a critical role in the carbon (C) cycle. However, the regulatory mechanisms underlying SOC dynamics across urbanization gradients in urban forests remain poorly understood. In this study, we investigated the interrelationships among plant diversity, SOC and its oxidation-stable fractions, and functional genes across an urbanization gradient encompassing an urban center (UC), subcenter, suburb, and exurb. Our findings revealed that urbanization significantly enhanced plant diversity and altered SOC dynamics. UC exhibited higher plant diversity and increased concentrations of active SOC fractions. Although urbanization did not significantly affect microbial α-diversity, it selectively enriched the relative abundance of specific taxa. C sequestration-related functional genes, particularly K15635 and K01965, were strongly associated with the regulation of SOC dynamics in the urban forest. Our findings underscore the importance of conserving diverse tree communities to enhance the C-sequestration function of urban forests.