Collaborative Research: Understanding Ozone-Ecosystem Controls and Feedbacks across Landscapes through Leaf- and Canopy-Scale Measurements

这项研究将有助于更好地理解影响森林地区对流层臭氧变化的过程。将使用新的分析工具来收集对大气-树冠气体交换以及与之相关的臭氧生态反应的综合观测。领导这项工作的跨学科科学家团队拥有大气化学、景观和生物生态学、陆地-大气交换方面的专业知识，以及在现场和实验室环境中设计和使用先进仪器方面的广泛实验专业知识。该项目的结果有可能通过更好地反映生态系统对臭氧污染的反馈来改进空气质量模拟。科学家团队计划在弗吉尼亚州中部的弗吉尼亚森林实验室(VFL)收集两年的连续数据，将臭氧通量测量与通过太阳诱导荧光(SIF)观测树冠水平的光合作用、同分异构体分解的臭氧反应性生物有机化合物(BVOCs)以及树冠电导和二氧化碳交换的关键生态系统参数相结合。这些变量将通过叶尺度实验室实验中的类似仪器进行测量，在典型的本地环境条件下，使用VFL中突出的植物物种，其中将诱导扰动来测试生态系统反馈。将被测试的三个假设是：(1)进入树冠的臭氧通量与SIF技术之间的相互作用，直接检测到叶绿素分子的荧光，是可直接测量的，独立于臭氧通量和气孔导度之间的相互作用，并对臭氧寿命有明显的影响；(2)进入树冠的臭氧通量通常由测量稀少但活性很高的BVOCs控制。由这些BVOC引起的冠层臭氧通量的变化可以通过它们的分子特性和浓度来量化；(3)：植物吸收臭氧导致3个可检测到的和重要的臭氧生态系统反馈中的一个或多个：(A)臭氧吸收减少气孔导度，导致相对于植物吸收的臭氧寿命更长；(B)臭氧吸收通过损害光合作用而降低冠层BVOC浓度，导致更长的臭氧寿命，防止冠层内化学氧化；(C)臭氧吸收增加BVOC排放，导致针对冠层内化学氧化的更短的臭氧寿命。这项研究的结果预计将在大气成分和生态系统功能之间的关系上产生新的观测约束。这一奖项反映了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。

This research will help to develop a better understanding of the processes that influence tropospheric ozone variability in forested regions. New analytical tools will be used to collect comprehensive observations of the atmosphere-canopy exchange of gases and the associated ecological response to ozone. The interdisciplinary team of scientists who are leading this effort have expertise in atmospheric chemistry, landscape and organismal ecology, and land-atmosphere exchange, as well as broad experimental expertise in advanced instrumentation design and use in field and laboratory settings. The results of this project have the potential to improve air quality modeling by better representing ecosystem feedbacks to ozone pollution. The team of scientists plan to collect two years of continuous data at the Virginia Forest Laboratory (VFL) in central Virginia, coupling ozone flux measurements with observations of canopy-level photosynthesis by solar induced fluorescence (SIF), isomer-resolved ozone-reactive biogenic organic compounds (BVOCs), and critical ecosystem parameters of canopy conductance and carbon dioxide exchange. These same variables will be measured by analogous instrumentation in leaf-scale laboratory experiments using plant species prominent at the VFL under the range of typical local environmental conditions, in which perturbations will be induced to test for ecosystem feedbacks.The three hypotheses to be tested are: (1) Interactions between ozone flux to the canopy and the SIF technique, that directly detects fluorescence of chlorophyll molecules, are directly measurable, are independent from interactions between ozone flux and stomatal conductance and have a distinguishable effect on the ozone lifetime; (2) Ozone flux to the canopy is often controlled by sparsely measured but highly reactive BVOCs. Variability in ozone flux to the canopy caused by these BVOCs can be quantified by their molecular identities and concentrations; (3): Uptake of ozone by plants leads to one or more of 3 detectable and significant ozone-ecosystem feedbacks: (a) ozone uptake reduces stomatal conductance, leading to longer ozone lifetimes against plant uptake; (b) ozone uptake reduces canopy BVOC concentrations by impairing photosynthesis, leading to longer ozone lifetimes against within-canopy chemical oxidation; and (c) ozone uptake enhances BVOC emissions, leading to shorter ozone lifetimes against within-canopy chemical oxidation. The results of this research are expected to produce new observational constraints on relationships between atmospheric composition and ecosystem function.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.