Soil pore architecture regulates carbon persistence via anaerobic microsites

Orly Mendoza , John Koestel, Luca Bragazza, Thomas Guillaume, Benita Putlitz, Adriano Sofo, Mohammad Yaghoubi, Heleen Deroo, Emily Lacroix, Marco Keiluweit, Georges Ndzana, Stéphanie Grand, Meret Aeppli 

Enhancing soil organic carbon (SOC) persistence in agricultural soils is a promising lever for climate mitigation, but realizing this potential depends on management practices that reliably promote SOC stabilization. Physical protection of organic compounds within soil aggregates is widely invoked to explain carbon stabilization under no-till farming, yet the role of pore architecture in regulating oxygen supply to microorganisms and its consequences for SOC turnover remains mechanistically unresolved. Here we show that no-till management promotes SOC persistence by selectively expanding a microbially accessible pore domain prone to oxygen limitation, thereby fostering anaerobic microsite development independently of soil texture without suppressing bulk carbon decomposition. Integrating pore network imaging, oxygen transport measurements, microbial functional gene quantification, and carbon mineralization experiments, we demonstrate that no-till specifically expands the 1–30 µm pore domain and elevates anaerobic microbial functional potential, while soil texture governs bulk oxygen supply and carbon turnover. These findings reframe physical protection as an oxygen-mediated, pore-scale mechanism responsive to agricultural management that complements mineral-associated carbon stabilization, with implications for soil carbon modeling under changing land management and climate.