Collaborative Research: RUI: Will climate change lead to system shifts on tropical mountains?: the interplay of epiphyte losses on host tree function, microclimate, and hydrology

热带山地云林 (TMCF) 因其极高的生物多样性以及这些森林在当地和区域水循环中发挥的关键作用，成为值得研究和保护的重要生态系统。由于云底上升和干旱条件加剧，低地地区的森林砍伐和全球海洋表面温度的升高间接威胁着这些森林。附生植物，即生活在其他植物表面的植物，几乎覆盖了 TMCF 中的所有树木表面，并且由于其捕获和临时储存水分的能力很强，对生态系统功能做出了重大贡献。不幸的是，这些植物是最容易受到预计气候变化影响的生态系统组成部分。 TMCF 中附生植物的丧失将导致生物多样性的大量丧失以及人类水资源的不稳定。这项工作旨在填补 TMCF 中对附生植物和森林功能反馈理解的重要空白，并将为土地利用和保护工作者以及关心长期水安全的热带山地地区自然资源管理者和政府提供重要数据。许多本地和美国的工人和学生将接受现场和实验室技术培训，所有参与者将定期举办培训活动和交流。将创建附生植物花园和配套课程，并将其放置在当地学校，以提高对云林附生植物和水循环之间联系的理解和认识。由于气候的快速变化，热带山地云林（TMCF）正面临威胁，事实上，最近的研究表明，该生态系统预计在未来几十年内将大幅收缩。该提案解决了以下问题：TMCF 中多样化和丰富的附生植物群落的丧失将如何影响树木健康、能量平衡和水文功能？研究人员提议进行首次大规模附生植物去除实验，其中森林和牧场中的树木将被剥夺整个附生植物群落。将在去除附生植物的树木内部和之下测量冠层小气候（气温、相对湿度、叶子湿度、风速、太阳辐射）以及生长、水分关系（水势、液流、气孔特征、碳同位素）和生态水文参数（土壤湿度、径流、茎流）的变化，并与具有完整附生植物群落的配对树木进行比较。使用配备集成多光谱成像系统的高精度无人机，将进行直接现场测量与遥感参数（NDVI、气温、叶子含水量）相结合。将开发附生植物与寄主树木水关系的数值模型，并将其与陆地表面水文模型相结合，以扩大实地测量规模并预测附生植物损失对区域能源预算和冠层水循环的影响。实地工作将在哥斯达黎加中部蒙特维多地区的五个地点进行。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Tropical Montane Cloud Forests (TMCFs) are important ecosystems to study and conserve due to their exceedingly high biodiversity as well as the critical roles these forests play in local and regional water cycling. Deforestation in lowland regions and increases in global sea surface temperatures indirectly threaten these forests due to the lifting of the cloud base and an increase in drought conditions. Epiphytes, i.e. plants that live on the surfaces of other plants, cover nearly all tree surfaces in the TMCF and contribute substantially to ecosystem function due to their high capacity to capture and temporarily store water. Unfortunately, these plants are the most vulnerable ecosystem components to projected changes in climate. A loss of epiphytes in the TMCF would lead to substantial biodiversity loss as well as a destabilization of water resources for human populations. This work aims to fill an important gap in the understanding of feedbacks among epiphytes and forest functions in the TMCF, and will provide important data for land-use and conservation workers as well as natural resource managers and governments in tropical montane regions concerned with long-term water security. A number of local and US-based workers and students will be trained in field and lab-based techniques and regular training events and exchanges will take place amongst all the participants. Epiphyte gardens and accompanying curriculum will be created and placed in local schools to increase understanding and awareness of the connectivity between epiphytes and water cycling in the cloud forest. Tropical Montane Cloud Forests (TMCFs) are under threat due to rapid changes in climate and in fact, recent work suggests that this ecosystem is predicted to contract substantially in the coming decades. This proposal addresses the question: How will a loss of the diverse and abundant epiphyte communities in the TMCF impact tree health, energy balance and hydrologic function? The investigators propose to conduct the first large-scale epiphyte removal experiment, in which trees in forest and pasture will be stripped of their entire epiphyte community. Changes in crown-level microclimate (air temperature, relative humidity, leaf wetness, wind speed, solar radiation) as well as growth, water relations (water potential, sap flow, stomatal traits, carbon isotopes) and ecohydrological parameters (soil moisture, throughfall, stemflow) will be measured in and under the trees stripped of their epiphytes and compared with paired trees with intact epiphyte communities. Direct field-based measurements will be coupled with remotely sensed parameters (NDVI, Air Temperature, Leaf Water Content) using a high-precision drone outfitted with an integrated multispectral imaging system. A numerical model of epiphyte-host tree water relations will be developed and coupled to a land-surface hydrology model to scale up the field-based measurements and predict the effect of epiphyte loss on regional energy budgets and canopy water cycling. Field work will take place in five locations in the Monteverde Region of Central Costa Rica.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.