DISSERTATION RESEARCH: Assessing urbanization impacts on canopy epiphyte biodiversity and function in Pacific Northwest forests.

论文研究：城市云中的冠层：评估城市化对太平洋西北森林冠层附生植物生物多样性和功能的影响虽然规模相对较小，太平洋西北部森林树冠上生长的地衣和苔藓对森林的运作有很大的影响。它们的一个作用是在这些森林生态系统中进行养分循环。地衣和苔藓虽然重要，但对城市污染的沉降物特别敏感。初步研究表明，暴露于城市污染物可能导致太平洋西北部森林树冠中苔藓和地衣群落的急剧变化，包括完全丧失非常敏感但具有生态重要性的地衣，这些地衣可以从空气中捕获氮。虽然这些地衣的极端敏感性使它们特别容易受到大气污染的影响，但迄今为止，还没有研究评估城市环境的蔓延对这些森林冠层地衣群落的影响，也没有研究评估营养物质在冠层中的使用情况。这一点尤其重要，因为整个太平洋西北地区的运输和运输来源的污染物增加。这项研究将创造重要的新的理解日益增长的城市环境对附近的树冠和太平洋西北部森林生态系统的影响。这里获得的结果将有助于估计森林通过污染获得多少氮。总的来说，这些努力将帮助研究人员和政府机构在太平洋西北部快速增长的城市中心周围确定有被破坏风险的树冠区域。与人类改变生态系统有关的生物多样性丧失是全球的一个主要问题，全球城市地区的迅速扩张助长了这种丧失。城市化可以用广布的通才物种取代特有物种，造成一个同质化的生态系统，从而对生态系统功能产生影响。虽然许多研究已经确定土地使用变化是陆地生物多样性丧失的主要驱动因素，但迄今为止，相对较少的研究探讨了城市空气羽流的迁移和暴露于顺风生态系统如何也可能导致现代生物多样性丧失。太平洋西北部以其许多原始的、标志性的针叶林而闻名，这些针叶林拥有巨大的生物量和林冠附生植物（地衣和苔藓）的生物多样性。最近，太平洋西北地区经历了快速的人口增长和许多特有的树冠附生植物物种是非常敏感的城市化的影响（增加活性氮和重金属沉积）。本研究旨在评估城市引起的附生植物群落结构的变化如何影响太平洋西北地区森林生态系统的过程，通过研究冠层附生植物群落的变化如何影响冠层氮循环。本研究将解决冠层cyanolichen固氮率如何在一个既定的区域城市化梯度的变化，并解决整体贡献的苔藓相关的固氮潜力在花旗松树冠层，以前未确定的冠层固氮源在太平洋西北森林。

---------------------------------------------------------DISSERTATION RESEARCH: Canopies in the urban cloud: assessingurbanization impacts on canopy epiphyte biodiversity and function inPacific Northwest forestsWhile relatively small in size, the lichens and mosses growing in forest canopies in the Pacific Northwest have a big impact on how the forest works. One role they perform is the cycling of nutrients in these forested ecosystems. Although important, lichens and mosses are especially sensitive to the fallout from urban pollution. Preliminary studies indicate that exposure to urban pollutants may lead to dramatic shifts in the moss and lichen communities in forest canopies of the Pacific Northwest, including the total loss of very sensitive, yet ecologically important, lichens that can capture nitrogen from the air. Although the extreme sensitivity of these lichens makes them particularly vulnerable to atmospheric pollution, to date there has been no study to assess the impacts of the spread of urban environments on these forest canopy lichen communities or how nutrients are used in the canopy. This is particularly important as transportation and transportation-sourced pollutants increase throughout the Pacific Northwest. This research will create important new understanding of the impacts of growing urban environments on nearby tree canopies and forested ecosystems of the Pacific Northwest. The results obtained here will be useful to estimate how much nitrogen forests receive through pollution. Collectively, these efforts will aid researchers and government agencies in identifying canopy areas at risk of being damaged around the rapidly increasing urban centers in the Pacific Northwest. Biodiversity loss associated with human alteration of ecosystems is a major planetary concern, and rapid expansion of global urban areas contributes to this loss. Urbanization can replace endemic species with widespread generalist species, creating a homogenized ecosystem with resulting impacts on ecosystem function. While many studies have identified land-use change as the main driver of terrestrial biodiversity loss, relatively few studies, to date, have explored how the transport and exposure of urban air plumes to downwind ecosystems may also be driving modern biodiversity loss. The Pacific Northwest is known for its many pristine, and iconic, coniferous forests that harbor an immense biomass and biodiversity of canopy epiphytes (lichens and mosses). Recently, the Pacific Northwest has experienced rapid population growth and many endemic tree canopy epiphytic species are extremely sensitive to the increasing effects of urbanization (increasing reactive nitrogen and heavy metal deposition). This research aims to assess how urban-induced shifts in epiphyte community structure influence Pacific Northwest forest ecosystem process by examining how community shifts in canopy epiphytes affect canopy nitrogen cycles. This study will address how rates of canopy cyanolichen nitrogen fixation vary across an established regional urbanization gradient and address the overall contribution of moss-associated nitrogen fixation potential in Pseudotsuga menziesii tree canopies, a previously unidentified source of canopy nitrogen fixation in Pacific Northwest forests.