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

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

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.