Faster-and-tighter nitrogen cycle supports mature forest productivity under elevated CO₂.

Authors

Manon Rumeau, Carolina Mayoral, Fotis Sgouridis, Michaela K Reay, Yolima Carrillo, Richard J Norby, Liz Hamilton, Iain P Hartley, Gianni Micucci, Emma Sayer, A Rob Mackenzie, Sami Ullah

Published in

Science advances. Volume 12. Issue 31. Pages eaed2732. Jul 31, 2026. Epub Jul 29, 2026.

Abstract

Rising atmospheric carbon dioxide (CO₂) concentration could enhance forest carbon (C) uptake, but nitrogen (N) is thought to progressively constrain this effect. Yet, significant biomass gains were demonstrated in a mature oak forest after 6 years of Free Air CO₂ Enrichment. This study investigates whether changes in soil N fluxes explain these gains. We show that enhanced N mineralization and ecosystem N conservation support increased productivity under elevated CO₂ (eCO₂). In situ net and gross N ammonification was enhanced by ∼30%, with a pronounced effect at oak budburst. Higher N ammonification rates were associated with increases in both fine root biomass and soil respiration. Gross nitrification was reduced, revealing a faster-yet-tighter cycle facilitated by plant-soil interactions. Hence, forest N cycling can adapt to support C uptake under eCO₂, but in the longer term, this capacity may be constrained by soil-accessible organic N stocks and reductions in anthropogenic N deposition.

PMID:
42525776
Bibliographic data and abstract were imported from PubMed on 13 Oct 2026.

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