Collaborative Research: Seeing the forest with the leaves--inferring plant habit and ecophysiology from leaf fossils

合作研究：用树叶看森林——从树叶化石中推断植物习性和生态生理。Kevin Boyce1 &; Maciej A Zwieniecki2 (PIs)1。-芝加哥大学地球物理科学系，伊利诺伊州芝加哥60637.2哈佛大学阿诺德植物园，马萨诸塞州剑桥02138。离体叶片是最常见的植物大化石之一。由于叶片是植物与环境之间的主要界面，因此化石叶片形态已被广泛证明是有关过去气候和大气成分的宝贵信息来源。然而，从叶子的角度来看，叶子所附着的植物就像区域气候一样是其环境的一部分。因此，树叶化石也可以保存有关亲本植物习性和生态以及景观植被结构的未开发的信息财富。该项目的主要目标是利用对叶片结构和生理联系的新兴机制理解，从叶片化石中开发解剖学代理来解释整个植物生态生理的三个参数。1)植物习性——高大的乔木或低矮的灌木——是由叶脉密度的差异提供的，叶脉总数相似。2)在解剖保存的叶类化石中，叶脉和叶脉表面距离的比值提供了对水汽压不足（阳光、暴露的环境或阴凉的林下环境）的适应。3)叶片压缩过程中，碳同化和蒸腾能力由叶脉密度提供。这些工具将在热带和温带森林中进行系统发育和生态多样化的一系列实地测量，并进行温室和生长室实验，以模拟现代世界中不再存在的条件。第一个应用将集中在白垩纪/早期新生代开花植物多样化和晚古生代种子植物多样化的关键化石的生态生理学上，这是他们自己的关键主题，但对于将这些技术引入更大的古生物学界也很重要。关键的一点是，这些代理是基于已知的生理机制，而不仅仅是统计相关性。因此，所有对从泥盆纪的第一片树叶和森林到最近的任何时期的植物进化感兴趣的古生物学家都可以使用它们。这些工具将有助于化石的重建和对生理学和生态学进化的理解。更广泛地说，这项工作将为限制过去的气候和深时间的碳和水文循环提供一种新的方法。

COLLABORATIVE RESEARCH: SEEING THE FOREST WITH THE LEAVES--INFERRING PLANT HABIT AND ECOPHYSIOLOGY FROM LEAF FOSSILSC. Kevin Boyce1 & Maciej A Zwieniecki2 (PIs)1.-Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637.2. Arnold Arboretum of Harvard University, Cambridge, MA 02138.Detached leaves are among the most common of plant macrofossils. Because leaves are the primary interface between plant and environment, fossil leaf morphology has been widely proven to be a valuable source of information regarding past climates and atmospheric compositions. From the leaf's perspective, however, the plant to which the leaf is attached is as much a part of its environment as regional climate. Thus, fossil leaves may also preserve an untapped wealth of information concerning the habit and ecology of the parent plant as well as the vegetation structure of the landscape. The primary goal of this project is to develop anatomical proxies for interpreting three parameters of whole-plant ecophysiology from leaf fossils using the emerging mechanistic understanding of how leaf structure and physiology are linked. 1) Plant habit -tall tree or low shrub- is provided from variance in vein density between leaf compressions with similar total vein number. 2) Adaptation to water vapor pressure deficit -a sunny, exposed environment or a shaded, understory environment- is provided by the ratio of the vein-vein and vein-leaf surface distances in anatomically preserved leaf fossils. 3) Carbon assimilation and transpiration capacities are provided by the density of veins per leaf surface area in leaf compressions. These tools will be established with a phylogenetically and ecologically diverse series of field-based measurements in both tropical and temperate forests, as well as greenhouse and growth chamber experiments to simulate conditions that no longer exist in the modern world. First applications will focus on the ecophysiology of key fossils during the Cretaceous/Early Cenozoic diversification of flowering plants and the late Paleozoic diversification of seed plants - key topics in their own right, but also important for the introduction of these techniques to the larger paleontological community.A crucial point is that the proxies are based in understood physiological mechanisms, not just in statistical correlations. Thus, they will be available to all paleontologists interested in any period of plant evolution from the first leaves and forests in the Devonian through to the Recent. These tools will aid reconstruction of fossils and understanding of the evolution of physiology and ecology. More broadly, this work will provide a new approach for constraining past climates and the carbon and hydrological cycles of deep time.