Determining the Functional Basis for Increasing Liana Abundance in Neotropical Forests

热带森林曾被认为对全球气候变化具有抵抗力；然而，它们现在正在发生变化。在新热带森林中发生的最大结构变化之一是藤本植物相对于树木的丰度增加。这种发展令人担忧，因为藤本植物大大减少了树木的补充、生长、繁殖、生存和多样性。事实上，最近的证据表明，藤本植物数量增加的影响可能是如此强大，以至于它们改变了全球碳循环，这反过来又对持续的全球气候变化产生了严重影响。尽管藤本植物丰富度的增加可能产生深远的影响，但其原因仍然知之甚少。本研究将使用一系列前沿方法来解决生态学中的一个紧迫问题：什么是导致新热带森林向藤本植物优势转变的推定因素。考虑到热带森林对全球多样性和全球碳循环的重要性，拟议的研究是理解热带森林生态学、这些关键生态系统如何变化以及这些变化最终如何影响全球气候的基础。这项研究的更广泛影响包括为拉丁美洲的学生和生物学家进行教育和国际能力建设，以及指导美国的本科生和研究生。这项研究的结果将通过科学和大众新闻文章向公众传播，包括以专业摄影图像为特色的文章，说明重要的科学概念。鉴于有证据表明藤本植物在新热带森林中正在增加，并且藤本植物具有改变热带森林动态、组成和功能的能力和倾向，拟议的研究迫在眉睫，并将提供关于藤本植物增加速度和导致这些增加的假定因素的关键数据。确定热带森林藤本植物丰度的增加也将有助于更好地了解控制热带植物丰度和分布的因素，这是生态学的基本目标之一。本研究将结合多种方法（大规模人口统计学、精细生理学和生长以及多因素实验操作），确定巴拿马中部正在增加的藤本植物物种，确定解释这些物种增加的一系列形态和生理功能特征，并通过实验测试最可能导致藤本植物增加的因素（干扰、干旱、二氧化碳升高和氮沉积）。通过了解藤本植物增加的原因，该项目将解决重要的基础和应用生态问题。对来自美国和拉丁美洲的研究生和本科生以及生物学家的指导和培训是该项目的一个组成部分。

Tropical forests were once thought to be resistant to global climate change; however, they are now changing. One of the largest structural changes occurring in neotropical forests is the increase in liana abundance relative to trees. This development is alarming because lianas substantially reduce tree recruitment, growth, reproduction, survival, and diversity. In fact, recent evidence indicates that the effects of increasing lianas may be so powerful that they alter the global carbon cycle, which, in turn, has serious implications for continued global climate change. Despite the profound potential ramifications of increasing liana abundance, the causes remain poorly understood. This study will use a series of cutting-edge approaches to address a pressing question in ecology: what are the putative factors responsible for the shift towards liana dominance in neotropical forests. Considering the importance of tropical forests to global diversity and the global carbon cycle, the proposed research is fundamental to understanding the ecology of tropical forests, how these critical ecosystems are changing, and how these changes may ultimately influence global climates. Broader impacts of this research include educational and international capacity building for Latin American students and biologists, and the mentoring of US-based undergraduate and graduate students. Findings of this research will be communicated to the public through both scientific and popular press articles, including articles that feature professional photographic images that illustrate important scientific concepts. Given the evidence that lianas are increasing in neotropical forests and that lianas have the capacity and propensity to alter tropical forest dynamics, composition, and functioning, the proposed study is urgent and will provide critical data on the rate of liana increases and the putative factors responsible for these increases. Determining the increase in liana abundance in tropical forests will also allow a better understanding of the factors that control tropical plant abundance and distribution, one of the fundamental goals in ecology. Through a combination of approaches (large-scale demographic, fine-scale physiology and growth, and experimental manipulation of multiple factors), this research will identify the liana species in central Panama that are increasing, determine the suite of morphological and physiological functional traits that explain the increase in those species, and experimentally test the most likely factors responsible for liana increases (disturbance, drought, elevated CO2, and nitrogen deposition). By understanding the causes of liana increases, the project will address important basic and applied ecological issues. The mentoring and training of graduate and undergraduate students and biologists from both the US and from Latin America is an integral part of the project.