Permanent land use and microbial contributions shape soil carbon stabilization in lake floodplains

We examined how SOC storage and stabilization vary in the floodplain of Lake Saint-Pierre, along an anthropogenic disturbance gradient of six land uses: conventional and improved croplands, temporary and permanent meadows, marshes, and forested swamps. In all 6 land uses, we quantified SOC stocks, mineral-associated organic matter - C (MAOM-C), particulate organic matter - C (POM-C), soil δ13C and sugars.

Land use effects on SOC storage and stabilization were most pronounced in the topsoil (0-10 cm), with forested swamps showing the highest vegetation biomass, SOC, and MAOM-C. According to sugar analyses, microbe-derived inputs were more abundant in MAOM, which is more stable than POM, whereas plant-derived C dominated the latter. Soil C pools increased with decreasing disturbance, with a tipping point occurring in the transition from temporary to permanent meadows.