Roger Dixon

This PhD project investigates how forests respond to rising atmospheric CO₂ and increasing global temperatures, focusing on the critical but underexplored area of leaf thermoregulation. Forests are vital in regulating the global carbon and water cycles, but their resilience to climate extremes is uncertain. The ability of plants to regulate leaf temperature under fluctuating environmental conditions can determine their survival during extreme heat events. Recent studies indicate that tropical forests are nearing dangerous thermal limits, while temperate forests are experiencing increased heat stress. Elevated CO₂ may further increase leaf temperatures and the risk of leaf scorching, independent of heat events. Understanding how forests balance heat, water, and carbon dynamics—from individual leaves to entire canopies—is essential for predicting their future stability and their role in mitigating climate change. The doctoral researcher will use state-of-the-art Free-Air CO₂ Enrichment (FACE) facilities to expose mature woodlands to both warming and elevated CO₂. Research will be conducted at BIFoR-FACE in the UK (temperate), AmazonFACE in Brazil (tropical), and EucFACE in Australia (Eucalyptus), where forest plots have been exposed to high CO₂ for 9, 1, and 13 years, respectively. By installing 'leaf-heaters' and experimentally manipulating temperature, the student will investigate the mechanisms of leaf thermoregulation across different species, climates, and CO₂ levels, and test for interactions between CO₂ and warming. The project aims to assess changes in gas exchange, leaf temperature, critical thresholds, and leaf traits (such as light absorptance and chlorophyll fluorescence) under these conditions, as well as changes in carbon storage dynamics throughout the growing season. The student will collect data on photosynthetic capacity, carbon storage (including non-structural carbohydrate dynamics), and leaf thermal thresholds. The primary objective is to quantify the effects of heat and CO₂ on carbon uptake in different tree species, estimating the total potential carbon storage of various forest types under changing climates. This research will help identify which species are most efficient at capturing carbon during high temperatures and low water availability under variable CO₂, aiding predictions of how different forest types will respond to climate change. The findings will inform policy and forest management strategies, supporting conservation and the use of forests in climate change mitigation. The PhD student will be based at the University of Birmingham within the Birmingham Institute of Forest Research (BIFoR) and the School of Geography, Earth and Environmental Sciences, with collaborative fieldwork at AmazonFACE and EucFACE. The supervisory team includes Dr. Alice Gauthey (University of Birmingham), Dr. Sophie Fauset (University of Plymouth), Prof. Kristine Crous (Western Sydney University), Prof. Tomas Domingues (University of Sao Paulo), and Prof. Roger Dixon (University of Birmingham).