Impact of Elevated CO₂ and Temperature on Soil Carbon and Nitrogen Dynamics

Abstract

Elevated atmospheric carbon dioxide (eCO₂) and global warming are key drivers of climate change, with profound implications for soil carbon (C) and nitrogen (N) dynamics. This review synthesizes empirical findings, meta-analyses, and modelling studies to assess how eCO₂ and warming, both individually and in combination, alter soil C and N pools, fluxes, and feedback. Elevated CO₂ enhances plant photosynthesis, biomass production, and belowground carbon inputs, potentially stimulating short-term soil organic carbon accumulation. However, it also modifies microbial activity and nutrient demand, often leading to nitrogen limitation and priming effects that accelerate soil organic matter decomposition. Warming consistently increases microbial respiration and nitrogen mineralization, often resulting in carbon losses, particularly from subsoils. The interactive effects of eCO₂ and warming are frequently non-additive, shaped by ecosystem type, soil depth, moisture availability, and microbial community responses. The review highlights methodological advances including Free-Air CO₂ Enrichment (FACE), whole-profile soil warming, and stable isotope tracing, which have improved mechanistic understanding. Key knowledge gaps remain, particularly in subsoil processes, microbial function, and responses to extreme climate events. Management strategies such as precision nitrogen application, biochar amendments, and conservation tillage offer promising mitigation pathways. Overall, a systems-level, adaptive management approach informed by integrated field experiments and Earth system modelling is critical for enhancing soil resilience under climate change.