Urbanization weakens soil carbon stocks but enhances carbon stability through coupled physicochemical and microbial mechanisms in Beijing urban-rural forests.

Urban forest soils are important carbon (C) pools, and their C transformation processes are influenced by environmental changes driven by rapid urbanization. However, the mechanisms underlying soil organic C (SOC) storage and stability remain unclear. In this study, we investigated forest soils along an urban-rural gradient in Beijing from the physical (soil aggregates), chemical (13C NMR), and microbial (metagenomic sequencing) perspectives to elucidate SOC stabilization mechanisms. We found SOC content in urban soils was 20.97% lower than in suburban forests and 31.21% in rural forests, primarily due to reduced litter input and altered C turnover. The proportion of SOC within the silt-clay fraction was increased by 23.76%, indicating greater physical protection. The relative abundance of aromatic C and alkyl C were increased by 2.27% and 2.34%, respectively, suggesting enhanced chemical recalcitrance. Microbial analysis showed a 36.48% reduction in ectomycorrhizal fungi, a 36.28% decline in oxidative enzyme activities, and a 47.36% decrease in genes related to recalcitrant degradation, while genes and enzymes targeting labile C were enriched. These shifts constrained decomposition of recalcitrant compounds, reinforcing SOC persistence. Overall, urbanization reduces SOC storage but enhances SOC stability due to promoting fine-fraction association, chemical recalcitrance, and optimizing microbial community composition. These findings provide new insights into urban soil C sequestration and feedbacks to climate change.

• Publication year

  2025

• Venue

  Environmental Research

• Publication date

  2025-09-01

• Fields of study

  Medicine, Environmental Science

• Identifiers
  DOI 10.1016/j.envres.2025.122901PMID 40975419
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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