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

热带山地云雾林（TMCFs）是研究和保护的重要生态系统，因为它们具有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。低地地区的森林砍伐和全球海面温度的上升，由于云底的抬升和干旱情况的增加，间接威胁到这些森林。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，由于其捕获和临时储存水分的能力很高，因此对生态系统功能有很大贡献。不幸的是，这些植物是最容易受到气候变化影响的生态系统组成部分。TMCF中附生植物的损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中附生植物和森林功能之间反馈的理解方面的一个重要空白，并将为土地使用和保护工作者以及关注长期水安全的热带山区自然资源管理人员和政府提供重要数据。一些当地和美国的工人和学生将接受实地和实验室技术培训，所有参与者将定期举行培训活动和交流。将在当地学校建立附生植物园和相关课程，以提高对云雾森林中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，热带山地云雾林（TMCF）正受到威胁，事实上，最近的研究表明，这一生态系统预计将在未来几十年内大幅收缩。该提案解决了这样一个问题：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？研究人员建议进行第一次大规模的真菌清除实验，在该实验中，森林和牧场中的树木将被剥夺其整个真菌群落。冠层微气候（空气温度，相对湿度，叶片湿度，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（土壤水分，穿透，茎流）的变化将被测量和剥离的附生植物的树木下，并与配对的树木完整的附生植物群落进行比较。直接实地测量将与遥感参数（归一化差异植被指数、气温、叶片含水量）相结合，使用配备有综合多光谱成像系统的高精度无人驾驶飞机。将开发一个附生植物-宿主树木水分关系的数值模型，并将其与地表水文模型相结合，以扩大实地测量，并预测附生植物损失对区域能量收支和树冠水循环的影响。实地工作将在哥斯达黎加中部蒙特韦尔德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知识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.