Phosphorus enrichment does not enlarge the predicted CO₂ fertilization effect on forest carbon sequestration.

Authors

Bin Wang, He Lyu, Xueqian Zhang, Mingkai Jiang, Belinda E Medlyn, David Wårlind, Jürgen Knauer, Katrin Fleischer, Daniel S Goll, Stefan Olin, Xiaojuan Yang, Lin Yu, Sönke Zaehle, Haicheng Zhang, Kristian Schufft, Kristine Y Crous, Yolima Carrillo, Catriona A Macdonald, Ian C Anderson, Matthias M Boer, Mark Farrell, Andrew Gherlenda, Laura Castañeda-Gómez, Shun Hasegawa, Klaus Jarosch, Paul Milham, Raúl Ochoa-Hueso, Varsha Pathare, Johanna Pihlblad, Juan Piñeiro, Sally A Power, Peter B Reich, Markus Riegler, David S Ellsworth, Benjamin Smith

Published in

Proceedings of the National Academy of Sciences of the United States of America. Volume 123. Issue 12. Pages e2516152123. Mar 24, 2026. Epub Mar 19, 2026.

Abstract

The capacity of nutrient-limited forests to enhance carbon (C) sequestration under elevated CO₂ (eCO₂) remains a critical uncertainty in C cycle modeling. While existing evidence suggests that low phosphorus (P) bioavailability may constrain CO₂ fertilization effects on plant growth, the extent to which this limitation modulates ecosystem responses to eCO₂ in forests adapted to P-deficient soils remains poorly understood. Here, using eight P-enabled models, we simulated the magnitudes and mechanisms through which P bioavailability interacts with eCO₂, emulating an ecosystem-scale P enrichment experiment at a P-limited Eucalyptus forest undergoing long-term Free-Air CO₂ Enrichment. While models predicted pronounced P effects on tree growth, P enrichment unexpectedly did not increase the CO₂ effects on tree growth and ecosystem C sequestration. Models prioritized either CO₂-driven or P-driven growth, but rarely both. This tradeoff emerged due to model-specific assumptions on 1) partitioning of the extra P in soil labile versus nonlabile pools; 2) plant photosynthetic acclimation to P deficiency; 3) C and nutrient use strategies regulating plant size and allocation; and 4) microbial-driven soil decomposition processes. By generating divergent yet biologically plausible outcomes, these predictions establish critical testable hypotheses for empirical research and highlight multiple P-related pathways that may influence the future land C sink.

PMID:
41855264
Bibliographic data and abstract were imported from PubMed on 13 Oct 2026.

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