Collaborative Research: Dry in the sky? Ecophysiological Strategies and Drought Tolerance among Tropical Montane Cloud Forest Canopy Epiphytes

附生植物是一种以其他植物为食的植物，其多样性和丰度在热带山地云雾林（TMCF）中达到顶峰。在这个生态系统中，附生植物扮演着重要的生态系统角色，因为它们从雨和雾中拦截并保持营养和水分，并为许多鸟类、动物和昆虫提供食物和资源。由于这些植物无法从地下获得土壤和水分，它们特别容易受到气候变化的影响，包括云层高度的增加和干旱。这项研究将确定附生植物群落在多大程度上容易受到降水或云量减少和森林破碎化加剧的影响。该项目还将为哥斯达黎加蒙特韦德的生态旅游经营者制定树冠生态学培训方案。该地区每年接待超过10万人参加树冠探险运动，但很少有游客或导游了解TMCF的总体重要性，特别是附生植物群落的重要性。该小组还将为蒙特维德地区的当地研究和教育机构提供培训和演讲，包括蒙特维德保护区、蒙特维德研究所和当地高中。尽管有证据表明，林冠群落作为一个整体对生态系统过程很重要，但关于林冠群落抵御预计的气候变化和/或因毁林而增加的暴露能力的信息很少。在TMCF中，冠层的生长形式有很大的变化，这可能在它们对降水减少或云底高度增加的脆弱性方面有所不同。虽然已经努力了解个别物种对干旱胁迫的反应，但对干旱胁迫反应的变异性和植物应对预计未来干旱条件的能力知之甚少。通过在这个高度多样化但研究相对不足的系统中工作，本研究将增加对植物生态生理学基本主题的理解：植物对干旱的多种反应方式。六个地点的小气候变化提供了一个独特的机会，可以识别不同功能群的干旱胁迫响应，并确定这些特征是否随环境变化而变化，或者是塑性响应。功能形态特征、水分关系、水分利用和对干旱的脆弱性将在整个梯度上进行测量，以记录暴露于不同小气候下植物生态生理策略的变化。还将利用稳定同位素沿梯度评估光合作用策略。开阔牧场树木的冠层群落也将被研究，因为在给定的降水条件下，这些暴露的群落往往会经历更大的水压力，并可能提供关于冠层群落如何可能受到干旱压力或森林破碎化增加的影响的见解。为了评估一系列功能性状对抗旱性的作用，将对来自森林和牧场的三个地点（最潮湿、中间、最干燥）的一组常见物种进行操纵干旱实验。

Epiphytes, plants that live on other plants, reach their peak of diversity and abundance in Tropical Montane Cloud Forests (TMCF). In this ecosystem, epiphytes play important ecosystem roles because they intercept and hold on to nutrients and water from rain and mist and provide food and resources for many birds, animals and insects. Because these plants do not have access to soils and water from the ground, they are particularly vulnerable to changes in climate, including increases in cloud height and drought. This research will determine the degree to which epiphyte communities are vulnerable to decreases in precipitation or cloud cover, and increased forest fragmentation. This project will also develop a training program in canopy ecology for ecotourism operators in Monteverde, Costa Rica. This region hosts over 100,000 people per year for canopy adventure sports but few tourists or guides get information on the importance of the TMCF in general and the epiphyte community specifically. The team will also provide training and presentations to local research and educational institutions in the Monteverde region including the Monteverde Reserve, the Monteverde Institute and local high schools.Despite evidence that the canopy community as a whole is important to ecosystem processes, there is little information regarding the ability of this community to withstand projected changes in climate and/or increases in exposure due to deforestation. In the TMCF, there is great variation in growth forms in the canopy that may differ in their vulnerability to decreases in precipitation or increases in cloud base heights. Although efforts have been made to understand individual species responses to drought stress, little is known about variability in drought-stress responses and the ability of plants to cope with projected future drought conditions. By working in this hyper-diverse, but relatively understudied system, this research will increase the understanding of a fundamental topic in plant ecophysiology: the diverse ways plants respond to drought. Variability in microclimate across the six sites provides a unique opportunity to identify suites of drought-stress responses across functional groups and determine whether these traits vary, or respond plastically, to changes in the environment. Functional morphological traits, water relations, water use, and vulnerability to drought will be measured across the gradient to document variation in ecophysiological strategies in plants that are exposed to different microclimates. Photosynthetic strategies will also be evaluated along the gradient using stable isotopes. Canopy communities in open pasture trees will also be studied because these exposed communities tend to experience greater water stress within a given precipitation regime and may provide insights on how canopy communities are likely to be affected by increases in drought stress or forest fragmentation. To assess the role of suites of functional traits on drought resistance, a subset of common species from three of the sites (wettest, intermediate, driest) from both forests and pastures will be subjected to a manipulative drought experiment.