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--从树叶推断植物习性和生态生理。Kevin Boyce1和Maciej A Zwieniecki2(PI)1.-芝加哥大学地球物理科学系，芝加哥，IL 60637.2。马萨诸塞州剑桥市哈佛大学的阿诺德植物园，离叶是最常见的植物大型化石之一。由于叶片是植物和环境之间的主要界面，化石叶片的形态已被广泛证明是关于过去气候和大气成分的有价值的信息来源。然而，从树叶的角度来看，树叶所依附的植物既是区域气候的一部分，也是环境的一部分。因此，化石树叶还可以保存大量关于母植物的习性和生态以及景观的植被结构的未开发的信息。该项目的主要目标是开发用于从叶片化石中解释全植物生态生理学的三个参数的解剖学代理，利用对叶片结构和生理如何联系的新兴机制的理解。1)植物习性--高大乔木或低矮灌木--是由叶脉总数相近的叶片间叶脉密度的差异提供的。2)对水汽压力不足的适应--阳光充足的裸露环境或阴暗的林下环境--是由解剖保存下来的叶子化石中脉-脉和脉-叶表面距离的比率提供的。3)碳同化和蒸腾能力由叶压缩时单位叶表面积上的叶脉密度提供。这些工具将在热带和温带森林中进行一系列基于系统发育和生态多样性的实地测量，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/早新生代关键化石的生态生理学上，开花植物的多样化和晚古生代种子植物的多样化--这些主题本身是关键的，但对于将这些技术引入更大的古生物界也很重要。关键的一点是，这些替代技术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植物进化时期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和生态进化的理解。更广泛地说，这项工作将为限制过去的气候以及深部时间的碳循环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.