Understanding tree architecture, form and function in the tropics

树的基本形状和分支结构可以是独特的和特征的，但是没有一致的数据集来量化树的形状如何在物种之间变化，以及它如何与树的其他功能特征相关。了解树木结构和形态的变化对于将树木生理学与树木性能、树木内部和树木之间的水和碳的尺度通量联系起来，以及了解树木生长和死亡的制约因素非常重要。这些主题在生态系统科学领域具有重要意义，特别是考虑到当前和未来的气候变化。因此，令人惊讶的是，树的结构和形式是目前被忽视的研究领域。造成这种忽视的主要原因有两个：1)原位量化树形结构既困难又耗时；2)缺乏将树形参数与生理功能明确联系起来的理论。技术和理论的最新发展现在使我们能够克服这些限制。在本提案中，我们的目标是使用新的地面3D地面激光扫描技术（TLS）结合最近开发的理论框架来测量和比较树形结构。我们将重点放在热带地区，因为（一）热带地区拥有绝大多数阔叶树的多样性，在全球和区域碳和水通量中发挥着不成比例的作用；（二）热带森林的物种多样性很高（通常为每公顷100-250种树种），这意味着我们可以在几乎相同的气候和土壤条件下对大量物种进行采样。使它更有可能发现树木对环境的反应的总体趋势，而不是由特定物种的特性所主导的。具体来说，我们将使用TLS从不同环境的成熟雨林树木中收集高度详细的3D结构信息，从云雾森林到潮湿雨林再到干燥的稀树草原，并从安第斯山脉的云雾森林到亚马逊和非洲的豆科植物为主的森林，通过婆罗洲以龙脑科植物为主的高大森林，再到澳大利亚的古老雨林植物区系，对比生物地理历史。所有的野外地点都是我们已经收集了一些热带树木的叶子和木材特征信息的地点。我们计划实现三个目标：i)使用先进的成像和计算技术定义树形的定量类别，ii)发展对树形与树叶和木材功能性状之间协方差程度的理解，以及树形的系统发育约束和可塑性程度，iii)测试和改进基于代谢缩放的方法，以研究热带树木群落的缩放通量和生产力。在三年的时间里，我们的团队将：1)创建一个从我们的野外活动中收集的分支和冠层特征数据的数据库。2)利用分支结构和冠层结构特征的变化来定义一套分支和冠层特征，从而对树的形态进行分类。3)评估树木内部树形特征的尺度，将树形尺度整合到植物尺度机制框架中。4)探索树形性状与叶片和木材性状之间的联系，确定全树综合经济谱。在这样做的过程中，我们希望在大的空间尺度上对树的形式、功能、系统发育和环境之间的关系有一个机械的理解。我们期望发现，在树木令人眼花缭乱的各种形状和形式背后，隐藏着基于基本、共享原则的非常相似的建筑。

The basic shape and branching structure of a tree can be distinctive and characteristic, yet there exists no consistent dataset quantifying how tree form varies across species and how it is related to other functional traits of a tree. Understanding the variation in structure and form of trees is important in order to link tree physiology to tree performance, scale fluxes of water and carbon within and among trees, and understand constraints on tree growth and mortality. These topics hold great importance in the field of ecosystem science, especially in light of current and future changes to climate. It is surprising, therefore, that tree structure and form are currently neglected areas of study. There are two primary reasons for this neglect: 1) it is difficult and time-consuming to quantify tree structure in-situ and 2) there is a lack of theory that explicitly links tree form parameters with physiological function.Recent developments in technology and theory now enable us to overcome these limitations. In this proposal we aim to use new ground-based 3D terrestrial laser scanning technologies (TLS) in combination with recently developed theoretical frameworks to measure and compare tree architecture. We focus on the tropics, since (i) they host the vast majority of broadleaf tree diversity and play a disproportionate role in global and regional carbon and water fluxes, and (ii) the high species diversity of tropical forests (typically 100-250 tree species per hectare) means we can sample a large number of species under almost identical climate and soil conditions, making it more likely to detect overall tendencies in tree form response to environment that are not dominated by the peculiarity of a particular species. Specifically, we will employ TLS to collect highly-detailed 3D structural information from mature rainforest trees spanning contrasting environments ranging from cloud forests to wet rainforests to dry savanna, and contrasting biogeographical histories from the cloud forests of the Andes through legume-dominated forests of Amazonia and Africa, through the dipterocarp-dominated tall forests of Borneo, to the ancient rainforest flora of Australia. All field sites are locations where we have already collected information of the leaf and wood traits of a number of tropical trees. We plan to achieve three goals: i) definition of quantitative classes of tree form using advanced imaging and computational techniques, ii) development of an understanding of the degree of covariance between tree form and tree leaf and wood functional traits, and the degree of phylogenetic constraint and plasticity in tree form, iii) testing and refinement of metabolic-scaling based approaches to scaling fluxes and productivity of tropical tree communities. Over the course of three years our team will:1) Create a database of branch- and canopy-level trait data collected from our field campaigns. 2) Use variation in branching architecture and canopy structure traits to define a suite of branching and canopy traits that allow for the classification of tree form.3) Assess the scaling of tree form traits within trees and integrate the scaling of tree-form into a mechanistic plant scaling framework.4) Explore the link between tree-form traits and leaf and wood traits to determine a whole-tree integrated economics spectrum. In doing so, we hope to acquire a mechanistic understanding of the relationship between tree form, function, phylogeny and environment over a large spatial scale. We expect to find that behind the dazzling variety of shapes and forms found in trees hides a remarkably similar architecture based on fundamental, shared principles.