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

项目背景：热带森林中巨大的碳储量受到数量相对较少的大型树木的强烈影响。直径> 70厘米的树木平均含有25-45%的碳储量，但占热带森林树木数量的4%以下。2019年，在亚马逊河流域发现了一种突破性的树木，高度超过80米，比亚马逊河流域以前记录的其他树木高约30米，与婆罗洲发现的龙脑香树的大小更相似，婆罗洲是世界上已知最大的被子植物树家族，高度超过100米。然而，这些热带巨人在未来更热、更干燥的热带气候下的持久性仍然不确定。由于从根到叶的路径更长，重力的影响更大，因此将水输送到高大树木顶部的阻力更大，导致高大树木可能比小树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其输水系统以实现如此长距离的水输送缺乏基本了解，以及它们是否确实能够适应其输水系统以完全补偿与如此高相关的增加的水力压力。提高认识将使我们能够更好地预测大型热带树木的气候耐受性阈值。项目目的和方法：目的：解决一个关键的科学空白，即高大热带树木的水运输系统如何适应，使其能够达到超过80米的高度。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是通过在婆罗洲热带雨林进行广泛的实地考察，可以选择在巴西亚马逊地区进行实地考察，其中包括最近发现的亚马逊热带巨型树种Dinizia excelsa。这些目标是广泛的，如何解决这些目标的具体问题将通过候选人与监督团队共同设计一个尖端的实地研究计划来确定，以指定重点研究问题，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，其专业领域包括植物水力学，植物解剖学，树木结构，热带森林动力学和植被建模。这为候选人提供了一个研究专业的气息，在设计他们的研究时可以借鉴。

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.