NSFDEB-NERC: Addressing the plant growth C source-sink debate through observations, experiments, and modelling

Fossil fuel combustion, a primary contributor to rising atmospheric CO2 levels, is the main driver of climate change. Nevertheless, the rate of CO2 increase is slower than expected because the land and oceans together absorb approximately 50% of annual CO2 emissions. Some field studies indicate that a large portion of the land surface uptake is due to increasing tree growth, with the causes, locations, and future behaviour of this CO2 uptake remaining highly uncertain.

A common hypothesis suggests that increased CO2 levels boost plant photosynthesis and carbon uptake, while others argue that tree growth is not primarily limited by photosynthesis but by other factors like cell division rates, nutrients, or water supply. If true, this suggests that future CO2 uptake by land may be lower than currently assumed, leading to higher rates of climate change. Understanding plant responses to CO2 is crucial for policymakers to accurately predict the impacts of CO2 emission controls.

Therefore, the project aims to significantly improve our understanding of this fundamental issue using a unique combination of observations, experiments, and modelling. It will focus on mature individuals of white pine, red maple, and red oak growing in Harvard Forest, Massachusetts. This is an international collaborative project, with the modelling and detailed wood development work led by the University of Cambridge and the field and laboratory carbon measurement work led by Harvard University.