The role of mesophyll CO₂ diffusion in modulating the response of photosynthetic carbon uptake to CO₂ enrichment of a mature temperate forest
This project seeks to refine our understanding of how mesophyll recistance (rm) responds to environmental changes and whether plants can adjust rm over time. By combining advanced experimental techniques with mathematical models, the study will examine both immediate and long-term acclimation to elevated CO₂. The insights gained will improve the representation of photosynthesis in land surface models (LSMs), reducing uncertainty in predictions of vegetation carbon uptake and strengthening our ability to model climate–carbon cycle interactions.
The main aim of this project is to provide a new mechanistic understanding of leaf-level photosynthetic processes and adapt it to better constrain the carbon balance in future LSMs. We will achieve this by determining the mechanisms behind the variability of rm in response to the environment and whether plants can acclimate rm under long-term conditions.
To this end, we will advance the methodology to quantify rm under varying environments. We will integrate detailed experiments with mathematical modelling approaches to assess both instantaneous and acclimation responses to environmental changes, in particular to e[CO2]. The three key objectives of this project are: (1) Set up an experimental system that will allow us to separate rm into its functional components. This will be the basis to gain a mechanistic understanding of the variability of rm on a physiological level; (2) Assess the short-term responses of rm and its components to environmental variables such as [CO2], light and temperature in plants grown under controlled environments; (3) Test how these responses change with long-term acclimation to e[CO2] under controlled glasshouse conditions (in tree saplings) and the natural environment of BIFoR-FACE (in mature trees).
Applying these results to LSMs will allow us to better predict carbon uptake of plants in general and that of mature forest ecosystems in particular. The project ultimately aims at minimising the uncertainty in the magnitude of vegetation carbon uptake, the most important climate – carbon cycle feedback. It maps to, and thus links, the NERC research areas ‘Environmental physiology’ and ‘Biogeochemical cycles’.