Mechanistic responses of phosphorus-limited forests to CO₂ enrichment

Project leader, researchers and collaborators: Prof Ben Smith, Dr Catriona Macdonald, Prof David Ellsworth, Prof Anja Ramming, Dr David Wårlind

Funding period: 2022-2026

Funding agency: Australian Research Council

Project summary: Forests around the world absorb up to around a quarter of emissions from fossil fuel burning. This significantly slows CO₂ increase in the atmosphere, helping to dampen climate change.

However, we are still unsure of the geographic distribution of this so-called carbon sink, the processes and environmental factors that control it, and whether we can rely on forests to continue to absorb emissions under ongoing and future climate change.

These knowledge gaps hinder mitigation and adaptation planning, such as the protection of those forests that constitute the largest current and potential reservoirs for carbon. A key gap concerns the role of phosphorus, crucial in limiting the productivity of Australian woodlands as well as many tropical forests.

At EucFACE we are undertaking research that aims to close this vital knowledge gap. By initiating a CO₂ x P experiment we are investigating how P cycling and availability interact with elevated atmospheric CO₂ concentrations to control tree physiology and growth.

Further, we are examining the downstream effects on key above- and below-ground pools and fluxes of the carbon and phosphorus cycles. By assimilating data and insights from our experimental measurements in a process-based ecosystem model, we will encode new mechanistic understanding that allows us to extrapolate how rising CO₂ concentrations may impact the growth and carbon balance of forests on different soil types and in different climate zones of Australia and the world.

In this way, our research contributes to a better understanding of the future fate of the global forest carbon sink, and the scientific evidence base to underpin the sustainable management of the forests and their carbon stocks.