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了解影响森林地区对流层臭氧变率的过程。新的分析工具将用于收集有关大气-冠层气体交换和有关的臭氧生态反应的综合观测资料。领导这项工作的跨学科科学家团队在大气化学、景观和有机生态学以及陆地-大气交换方面具有专业知识，在先进仪器设计和野外和实验室环境中使用方面也具有广泛的实验专业知识。该项目的结果有可能通过更好地代表生态系统对臭氧污染的反馈来改进空气质量模型。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）、同分异构体分解臭氧活性生物源有机化合物（BVOCs）和冠层电导和二氧化碳交换的关键生态系统参数进行的冠层光合作用观测相结合。这些相同的变量将通过类似的仪器在叶级实验室实验中测量，在典型的当地环境条件范围内，使用在VFL突出的植物物种，其中将引起扰动以测试生态系统反馈。拟验证的三个假设是：(1)臭氧通量与直接检测叶绿素分子荧光的SIF技术之间的相互作用是可直接测量的，独立于臭氧通量和气孔导度之间的相互作用，对臭氧寿命的影响是可区分的；(2)林冠的臭氧通量通常由测量稀疏但活性高的BVOCs控制。这些挥发性有机化合物引起的林冠臭氧通量的变异可以通过它们的分子特性和浓度来量化；(3)：植物对臭氧的吸收会导致3种可探测的、重要的臭氧-生态系统反馈中的一种或多种：(a)臭氧吸收会降低气孔导度，导致相对于植物的吸收，臭氧寿命更长；(b)臭氧吸收通过破坏光合作用降低冠层BVOC浓度，导致更长的臭氧寿命以抵抗冠层内化学氧化；(c)臭氧的吸收增加了BVOC的排放，导致臭氧在冠层内化学氧化的寿命缩短。该研究结果有望为大气成分与生态系统功能之间的关系提供新的观测约束。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.