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

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

doi:10.1126/sciadv.aed2732

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

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^*

^*Corresponding author for this work

Geography, Earth and Environmental Sciences

Research output: Contribution to journal › Article › peer-review

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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.

Original language	English
Article number	eaed2732
Number of pages	9
Journal	Science Advances
Volume	12
Issue number	31
DOIs	https://doi.org/10.1126/sciadv.aed2732
Publication status	Published - 29 Jul 2026

Bibliographical note

Publisher Copyright:
© 2026 The Authors, some rights reserved

ASJC Scopus subject areas

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10.1126/sciadv.aed2732Licence: Creative Commons: Attribution (CC BY)

RumeauM2026FasterFinal published version, 1.69 MBLicence: Creative Commons: Attribution (CC BY)

Effects of simulated increase in nitrogen deposition on mature deciduous forests in the UK and Italy: above and belowground responses
Ullah, S. (Principal Investigator)
The Royal Society
31/03/22 → 30/03/24
Project: Research Councils
FACE underground: can trees in mature forests gain greater access to soil nutrients under elevated atmospheric CO2?
Ullah, S. (Principal Investigator)
NATURAL ENVIRONMENT RESEARCH COUNCIL
6/01/20 → 31/10/23
Project: Research Councils
Quinquennial (half-decadal) carbon and nutrient dynamics in temperate forests: Implications for carbon sequestration in a high carbon dioxide world
Ullah, S. (Co-Investigator), Shi, Z. (Co-Investigator), MacKenzie, R. (Principal Investigator) & Mayoral, C. (Co-Investigator)
NATURAL ENVIRONMENT RESEARCH COUNCIL
28/10/19 → 28/06/25
Project: Research Councils

Cite this

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title = "Faster-and-tighter nitrogen cycle supports mature forest productivity under elevated CO2",

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.",

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doi = "10.1126/sciadv.aed2732",

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AU - Rumeau, Manon

AU - Mayoral, Carolina

AU - Sgouridis, Fotis

AU - Reay, Michaela K.

AU - Carrillo, Yolima

AU - Norby, Richard J.

AU - Hamilton, Liz

AU - Hartley, Iain P.

AU - Micucci, Gianni

AU - Sayer, Emma

AU - Mackenzie, A. Rob

AU - Ullah, Sami

PY - 2026/7/29

Y1 - 2026/7/29

N2 - 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.

AB - 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.

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SN - 2375-2548

VL - 12

JO - Science Advances

JF - Science Advances

IS - 31

M1 - eaed2732

ER -

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

Abstract

Bibliographical note

ASJC Scopus subject areas

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Projects

Effects of simulated increase in nitrogen deposition on mature deciduous forests in the UK and Italy: above and belowground responses

FACE underground: can trees in mature forests gain greater access to soil nutrients under elevated atmospheric CO2?

Quinquennial (half-decadal) carbon and nutrient dynamics in temperate forests: Implications for carbon sequestration in a high carbon dioxide world

Cite this

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