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

---------------------------------------------------------论文研究：城市云中冠层：城市化对西北太平洋森林冠层附生植物生物多样性和功能的影响评估西北太平洋森林冠层中生长的地衣和苔藓虽然规模较小，但对森林的运作方式有很大的影响。它们的一个作用是在这些森林生态系统中循环养分。地衣和苔藓虽然重要，但它们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地区森林冠层苔藓和地衣群落发生巨大变化，包括能够从空气中捕获氮的非常敏感但具有重要生态意义的地衣的全部丧失。尽管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扩张对这些森林林冠地衣群落的影响，也没有研究评估林冠如何利用营养物质。这一点尤其重要，因为整个太平洋西北地区的交通和交通来源的污染物都在增加。这项研究将对不断增长的城市环境对太平洋西北地区附近树冠和森林生态系统的影响产生重要的新认识。这里得到的结果将有助于估计森林通过污染吸收了多少氮。总的来说，这些努力将帮助研究人员和政府机构确定太平洋西北部快速增长的城市中心周围有被破坏风险的冠层区域。与人类改变生态系统有关的生物多样性丧失是全球关注的一个主要问题，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，形成同质化的生态系统，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利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向顺风生态系统的运输和暴露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，这些针叶林蕴藏着巨大的生物量和生物多样性的冠层附生植物（地衣和苔藓）。近年来，太平洋西北地区人口增长迅速，许多特有的林冠附生物种对城市化的影响（活性氮和重金属沉积的增加）极为敏感。本研究旨在通过研究冠层附生植物群落变化对冠层氮循环的影响，评估城市诱导的附生植物群落结构变化对西北太平洋森林生态系统过程的影响。本研究将研究冠层蓝藻固氮速率如何在已确定的区域城市化梯度中变化，并研究西北太平洋森林冠层固氮源——蒙氏伪杉树冠层中苔藓相关固氮潜力的总体贡献。

---------------------------------------------------------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.