Scaling Tropical Giants: How Tree Height Influences the Functioning of Some of the World's Tallest Tropical Rain Forest Species

The large carbon stores held in tropical forests is strongly influenced by a small number of very large trees. Trees with a diameter greater than 70cm contain between 25-45% of the stored carbon, but represent fewer than 4% of the number of trees in tropical forests. However, the higher resistances associated with getting water along the longer path from root-to-leaf in tall trees and the greater impacts of gravity, makes taller trees likely to be more vulnerable to climate change, than smaller trees. Currently however, we lack a fundamental understanding of how tall trees adapt their water-transport systems to enable the transport of water over such large distances and whether they can indeed adapt their water transport systems to fully compensate for the increased hydraulic stresses associated with being so tall. Improved understanding will allow us to better predict the climatic tolerance thresholds of large tropical trees. This thesis address's this science gap by evaluating how key plant traits change with height in the world's largest tropical species and if the changes in structure and function with height make them more or less vulnerable to changes in climate. This objectives will be met through extensive field campaigns in Bornean tropical rainforest, with the PhD candidate co-designing a cutting-edge field research programme with the supervisory team, to specify focal research questions, of what to measure and how to measure it. As this studentship will compliment an existing NERC-funded research project, it involves joining a team of 15 world-renowned scientists, with specialisms ranging from plant hydraulics, plant anatomy, tree architecture, tropical forest dynamics and vegetation modelling. This provides the candidate with a breath of research specialism to draw upon, when designing their research.