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

Rabearison, T. J., Félix-Faure, J., Guillemette, F., Garneau, M., Martineau, C., Astorg, L., Chantigny, M., Favreau, V., Malko, J., Roy, A. et Maire, V. (2026). Permanent land use and microbial contributions shape soil organic carbon stabilization in lake floodplains. Soil Biology and Biochemistry, 220 . Article 110199. ISSN 0038-0717 DOI 10.1016/j.soilbio.2026.110199

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Résumé

Abstract

Floodplain ecosystems play a key role in soil organic carbon (SOC) storage, as they integrate inputs from both vegetation and deposited sediments. Promoting land uses with low anthropogenic disturbances helps maintain the function of these ecosystems as soil carbon (C) sinks. However, the tipping points along a disturbance gradient where land use transitions generate the largest SOC losses or gains remain unclear, though they are key for effective land use management and climate change mitigation. Because flood events can mobilize and enhance the loss of labile C, determining the main origin of stable SOC, whether from plants or soil microorganisms, is also important to identify the optimal combination of land use, vegetation, and soil type for SOC stabilization in floodplains. We examined how SOC stabilization and origin vary in the floodplain of Lake Saint-Pierre, Québec, Canada 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 at the same elevation, we quantified SOC stocks, mineral-associated organic matter - C (MAOM-C), soil δ13C and sugar biomarkers. Driven by land use change, variations in plant inputs were associated with changes in topsoil SOC storage. Forested swamps had the highest MAOM-C due to greater plant biomass inputs that increased both microbial- and plant-derived C. Across all land uses, microbial-derived sugars, particularly of fungal origin, were more abundant in MAOM than plant-derived sugars. Notably, MAOM remained below its saturation capacity. Soil C pools, including MAOM-C, and both microbial- and plant-derived C, increased nonlinearly with decreasing disturbance, with a tipping point occurring at the transition from temporary to permanent meadows. Our results highlight the importance of increasing both microbial- and plant-derived C inputs to promote SOC stabilization, while emphasizing the persistent key role of fungal metabolism in floodplain soils.

Type de document:	Article
Mots-clés libres:	Soil organic matter Carbon stabilization Carbon origin Tipping point Wetland Climate change
Date de dépôt:	08 oct. 2026 13:26
Dernière modification:	08 oct. 2026 13:26
Version du document déposé:	Version officielle de l'éditeur
URI:	https://depot-e.uqtr.ca/id/eprint/13158

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