Modeling Ozone Flux to Forests Across an Ozone Concentration Gradient in the Sierra Nevada Mountains, CA.

EPA Grant Number: R826601
Title: Modeling Ozone Flux to Forests Across an Ozone Concentration Gradient in the Sierra Nevada Mountains, CA.
Investigators: Goldstein, Allen H. , Panek, Jeanne A.
Institution: University of California - Berkeley
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 1998 through October 31, 2002
Project Amount: $621,367
RFA: Ecological Indicators (1998) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems


Tropospheric ozone is a pollutant which is responsible for forest damage worldwide. It is a potent oxidant which invades foliage through stomatal pores and impairs normal physiological function. Currently, there exist extensive ozone monitoring networks which measure ozone concentrations in remote forested locations throughout the US and Europe, however the physiologically relevant measure of potential ozone effects on forest health is the ozone flux, the amount of ozone which actually enters the foliage. We propose a method of utilizing routinely-measured meteorology to model ozone flux from ozone concentrations. We plan to develop this approach along a well-documented ozone concentration gradient in the Sierra Nevada Mts. of CA. Here, peak ozone flux is decoupled from peak ozone concentration both diurnally and seasonally, thus estimates of ozone dose (ppm-hours) do not adequately describe the times when forests are vulnerable to damage, nor the magnitude of the physiologically-relevant ozone. From our eddy flux work in a ponderosa pine stand, we have observed that peak ozone flux occurs in the early summer, while peak ozone concentrations occur in the late summer. Daily peak ozone flux precedes peak ozone concentrations by 2-4 hours.


Our model of canopy conductance will follow the approach of the FOREST-BGC (Forest Ozone Response Study-BioGeo Chemistry) family of models, but will be employed on an hourly time step to capture diurnal decoupling of ozone peak flux and concentration. Furthermore, we will test the use of foliage e13C as a proxy for stomatal conductance. To validate our modeling and e13C approach, we will measure gas exchange directly at 4 sites along the gradient and compare modeled to measured values of stomatal conductance and canopy conductance, and with these estimate ozone flux (ozone concentration canopy conductance). At the site where we have an eddy flux correlation tower we can further compare modeled values of canopy conductance, ozone deposition velocity and ozone flux with directly measured values. We will also use the physiology data to demonstrate that foliar e13C is an adequate proxy for stomatal conductance. Although visible injury has been measured on ponderosa and Jeffrey pine along the Sierra ozone gradient, no comprehensive physiological study has been established to complement that work. Such a study is necessary to link ozone damage to forest physiological processes such as water and carbon cycling.

Expected Results:

The methods described in this proposal will contribute to the accurate monitoring of California forest health in response to ozone pollution and should be applicable to forests in any place where there is ongoing ozone and meteorological monitoring.

Publications and Presentations:

Publications have been submitted on this project: View all 19 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 8 journal articles for this project

Supplemental Keywords:

forest ozone damage, modeling forest response, carbon isotopes, forest physiological processes, carbon cycling, water cycling, ozone deposition, pollution stress, RFA, Scientific Discipline, Air, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Forestry, Ecological Effects - Environmental Exposure & Risk, tropospheric ozone, Ecological Indicators, stressors, meteorology, forest ecosystems, ozone, ecosystem indicators, carbon storage, forests, pine trees, Sierra Nevada Mountains, atmospheric contaminants, California (CA), meteorological fluctuations

Relevant Websites: Exit EPA icon Exit EPA icon

Progress and Final Reports:

  • 1999 Progress Report
  • 2000 Progress Report
  • 2001 Progress Report
  • 2002
  • Final Report