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

热带山地云雾森林(TMCFs)是值得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，并且在当地和区域水循环中发挥着关键作用。低地地区的森林砍伐和全球海洋表面温度的上升间接威胁着这些森林，因为云层上升和干旱状况加剧。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，并由于其高度的捕获和临时储存水分的能力而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人口水资源的不稳定。这项工作旨在填补TMCF中附生植物之间的反馈和森林功能方面的一个重要空白，并将为土地利用和保护工作者以及热带山地地区关心长期水安全的自然资源管理者和政府提供重要数据。许多当地和美国的工人和学生将接受基于现场和实验室的技术培训，所有参与者将定期举行培训活动和交流。将创建附生植物园和配套课程，并将其放置在当地学校，以提高对附生植物与云雾森林中水循环之间的联系的理解和认识。由于气候的快速变化，热带山地云雾森林(TMCFs)正受到威胁，事实上，最近的研究表明，这个生态系统预计在未来几十年将大幅收缩。这项建议解决的问题是：失去林区丰富多彩的附生植物群落将如何影响树木的健康、能量平衡和水文功能？研究人员提议进行第一个大规模的真菌去除实验，在这个实验中，森林和牧场的树木将被剥夺其整个真菌群落。将测量树冠水平小气候(空气温度、相对湿度、树叶湿度、风速、太阳辐射)以及生长、水分关系(水势、树液流量、气孔特征、碳同位素)和生态水文参数(土壤水分、穿透雨、树干流量)的变化，并与具有完整附生植物群落的配对树木进行比较。直接基于现场的测量将与遥感参数(NDVI、气温、叶片水分含量)相结合，使用配备集成多光谱成像系统的高精度无人机。将建立附生植物-寄主树木水分关系的数值模型，并将其与陆地-地表水文模型相耦合，以扩大基于田间的测量并预测附生植物损失对区域能量收支和冠层水循环的影响。现场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智力优势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.