Scaling tropical giants: Understanding how tree height influences the function of the world tallest tropical rainforest species

项目背景：热带森林中储存的大量碳受到相对较少的非常大的树木的强烈影响。平均而言，直径70厘米的树木含有25-45%的碳储量，但在热带森林中所占的比例还不到4%。2019年，亚马逊地区突破性地发现了超过80米高的树木，比亚马逊地区以前记录的其他树木高约30米，尺寸与婆罗洲发现的龙脑树更相似，后者是世界上已知最大的被子植物树，高达100米。然而，在未来更热、更干燥的热带气候下，这些热带巨人的持久性仍不确定。从根到叶的路径较长，重力的影响更大，在将水输送到高大树木顶部的过程中，产生了更高的阻力，这导致高大的树木比矮小的树木更容易受到气候变化的影响。然而，目前，我们对高大的树木如何适应它们的水运系统来实现如此远距离的水运输，以及它们是否真的能够适应它们的水运系统来完全补偿与如此高相关的增加的水力压力，缺乏基本的了解。更好的理解将使我们能够更好地预测大型热带树木的气候耐受阈值。项目目标和方法：目标：解决关于热带高大树木的水运系统如何适应以使其达到超过80米的高度的关键科学空白。具体目标：评估世界上最大的热带物种的关键植物性状如何随高度变化评估结构和功能的变化是否使较大的树木更容易受到气候变化的影响这些目标将通过在婆罗洲热带雨林的广泛实地活动来实现，也可以选择去巴西亚马逊的网站，那里有最近发现的巨型亚马逊热带树种diizia excelsa。然而，这些目标是广泛的，如何实现这些目标的具体方法将通过候选人与主管团队共同设计一个前沿的实地研究计划来确定，以指定重点研究问题，测量什么以及如何测量。由于该奖学金将补充现有的nerc资助的研究项目，它涉及加入一个由15名世界知名科学家组成的团队，他们的专长包括植物水力学、植物解剖学、树木建筑学、热带森林动力学和植被建模。这为候选人在设计他们的研究时提供了一种研究专长。

Project Background:The immense quantities of carbon stored in tropical forests is strongly influenced by a relatively small number of very large trees.On average trees with a diameter >70cm contain between 25-45% of the stored carbon, but represent <4% of the number of trees in tropical forests. 2019 saw a ground-breaking discovery of trees in the Amazon exceeding 80m tall, ~30m taller than other trees previously recorded in Amazonia and more similar in size to the dipterocarp trees found in Borneo, the family containing the largest known angiosperm tree in the world, standing at >100m tall. However, the persistence of these tropical giants under future hotter, drier tropical climates remains uncertain.The impact of the higher resistances associated with getting water to the top of tall trees, which is generated by longer paths from root-to-leaf and greater impacts of gravity, results in taller trees being likely to be disproportionately 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.Project Aims and Methods:Aim: Address a critical science gap regarding how the water transport systems of tall tropical trees adapt to allow themselves to reach heights in excess of 80 meters.Specific Objective:Evaluate how key plant traits change with height in the world's largest tropical speciesEvaluate if the changes in structure and function make larger trees more vulnerable to changes in climateThese objectives will be met through extensive field campaigns in Bornean tropical rainforest, with the option to also sites go to sites in the Brazilian Amazon, housing the recently discovered giant Amazonian tropical tree species Dinizia excelsa.These objectives are however broad and specifics of how they can be addressed will be determined through the candidate co-designing a cutting-edge field research programme with the supervisory team, to specify focal research questions, 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.