DISSERTATION RESEARCH: Assessing cloud forest ecotone sensitivity to climate change in space and time

到本世纪末，极地北半球目前出现的显著气候和生态系统变化可能会席卷全球。例如，生物多样性的热带地区预计将变暖1-4摄氏度。热带气候变化已经很明显，表现为冰川融化、降水量减少、气温上升和厄尔尼诺/南方涛动更加频繁。该项目调查了美国夏威夷群岛哈雷卡拉火山上的热带生态系统对气候变化的敏感性。研究区域包含了一个变化的气候特征，即平均信风逆温，那里的云雾森林突然变成了灌木丛。热带山地云雾林具有丰富的特有物种，并提供水捕获和储存的重要生态系统服务，特别容易受到气候变化的影响。为了揭示气候如何影响今天的植被模式，该项目比较了从中高山草原到山地灌丛，再到穿过林线到云雾森林等生境中气候和植被的详细测量。这项研究还使用了保存在湖泊沉积物中的微化石来回顾过去，并调查了过去约10,000年来气候如何影响植被。最后，本研究分析了树心，以确定干旱是否控制了急剧的云雾森林上限。这项研究结合了不同时间尺度的分析，以预测热带生态系统的敏感性。这项研究的结果将指导来自哈雷卡拉国家公园、哈纳维自然区保护区和自然保护协会的管理人员，他们都积极参与控制入侵物种，并在这片独特的景观中保护稀有和濒危物种。

By the end of this century, the striking climate and ecosystem changes currently seen in the polar Northern Hemisphere will likely span the globe. The biodiverse tropics, for example, are projected to warm by 1-4 degrees C. Tropical climate change is already evident, in the form of melting glaciers, declining precipitation, increasing temperatures, and a more frequent El Nino/Southern Oscillation. This project investigates tropical ecosystem sensitivity to climate change on Haleakala volcano in the Hawaiian Islands, USA. The study area brackets a changing climatic feature, the mean trade-wind inversion, where the cloud forest abruptly switches to shrubland. Tropical montane cloud forests, which are rich in endemic species and provide the vital ecosystem service of water capture and storage, are particularly vulnerable to climate change. To reveal how climate affects vegetation patterns today, this project compares detailed measurements of climate and vegetation in habitats ranging from mesic alpine grassland, through montane shrubland, and across the forestline into cloud forest. This study also uses microfossils preserved in lake sediment to look into the past and investigate how climate affected vegetation over the past ~10,000 years. Finally, this study analyzes tree cores to determine whether aridity controls the sharp upper cloud forest limit. This study combines analyses across broadly different time scales to predict tropical ecosystem sensitivity. Results from this study will guide managers from Haleakala National Park, Hanawi Natural Area Reserve, and The Nature Conservancy who are all actively engaged in controlling invasive species and conserving rare and endangered species across this unique landscape.