Reviews and syntheses: Microbial Carbon Fixation in Dryland: A component of Global Carbon Cycle

Abstract. Atmospheric carbon dioxide (CO₂) sequestration is commonly attributed to plant-driven processes, while the contribution of soil microorganisms remains comparatively underexplored. This imbalance is particularly relevant in dryland ecosystems, which cover over 45 % of Earth’s land surface and store a substantial fraction of global soil organic carbon. Despite their vast extent and ecological significance, current frameworks often overlook the metabolic potential of microbial communities inhabiting these environments. In drylands, microorganisms have evolved diverse metabolic strategies to capture and store atmospheric carbon, supported by multiple carbon-fixation pathways that extend beyond the Calvin–Benson–Bassham cycle. Here, we examine microbial carbon fixation in dryland ecosystems as an underexplored component of the global carbon cycle. We highlight the diversity, metabolic flexibility, and stress adaptations of carbon-fixing microbes and discuss the dominant pathways supporting carbon assimilation under arid conditions. By integrating evidence across studies, the findings suggest that microbial processes in drylands can contribute to carbon sequestration in ways not fully captured by plant-centered perspectives. This review provides a framework for incorporating microbial metabolic diversity into current models of terrestrial carbon cycling and highlights its relevance for climate change mitigation strategies.