UPSC SeminarAndrew D. Friend
Department of Geography, University of Cambridge, Cambridge, UK
Title: Tree growth, the global carbon cycle, and climate
Host: Totte Niittylä
More information: https://www.geog.cam.ac.uk/people/friend/
Abstract of his talk:
The global natural land surface has been a substantial net sink of anthropogenic CO2 over recent decades (e.g. equivalent to 29% of fossil fuel plus land-use emissions over 2012-2021), reducing the rate of climate change. It is believed that forested ecosystems are a major contributor to this sink. However, we have a poor understanding of the causes of this imbalance, and hence have low confidence in our ability to predict future atmospheric CO2. The carbon balance of the land surface is typically viewed as being controlled by photosynthesis and heterotrophic respiration. However, plant growth (and hence carbon storage) is under direct control by biological factors and the environment independently of photosynthesis, suggesting current paradigms are at best incomplete. It is notable that global vegetation models disagree strongly on the relative attribution of the net land sink to different processes (especially to CO2 fertilization), and it is possible that this problem is at least partly due to their over-emphasis on photosynthesis parameterisations. Our research aims to improve understanding of controls on plant growth and how to incorporate this understanding into global models, shifting them away from the photosynthesis paradigm. We have developed a detailed model of xylogenesis that has provided insights into how wood formation is controlled, and are exploring formulations for coupling growth and photosynthesis at the whole-plant level in a new conceptual framework. Our model development is being supported by experimental and observational investigations into the physiological controls on wood formation at tissue and whole-plant levels in the hybrid poplar clone T89. Initial results from our new approach to modelling global vegetation carbon fluxes will be presented and remaining gaps in our understanding outlined.