Research Projects

Project at a Glance

Project Status: complete

Title: Impact of sulfur dioxide on vegetation: a sulfur dioxide-ozone response model

Principal Investigator / Author(s): Oshima, Ronald J

Contractor: Statewide Air Pollution Research Center, UC Riverside

Contract Number: A6-162-30

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Ecosystem Impacts, Modeling


The Statewide Air Pollution Research Center (SAPRC) at the University of California, Riverside (UCR) has a continuing mission to investigate the effects of air pollutants on vegetation, especially agricultural crops and forests, and to determine the losses in productivity caused by these pollutants. To further this mission, we have continued the Vegetation Loss Assessment Program using state-of-the-art procedures for evaluating air pollutant damage based on modeling and field observations. This research has provided information to be used by the Air Resources Board in assessing the impacts to vegetation of different ozone standards, and as a planning tool for guiding, future research, especially in terms of forest effects from ozone.

The overall project was initiated in early 1985. Phase I in 1985 focused on establishment of comprehensive computer data bases relevant to air pollutant, dose-respoarse data for important California crop species, a critical review of key plant studies, and sponsorship of a workshop to assess current data and address informational needs. Phase II in 1986 and 1987 focused on preparation of a detailed crop loss assessment based on 1984 data, "fine tuning" crop loss assessments with local agricultural input, and work to fill information gaps. Phase III began in 1987 and is continuing. It has emphasized the further refinement of crop loss models, interface of crop loss estimates with economic models to estimate economic losses, implementation of a field verification program to assess ozone exposures and associated crop effects at different locations in the state, and development of procedures and models for assessing losses to forests by focussing on key tree species.

Specific tasks for the 1988-89 were as follows: ( 1) hold a workshop in the San Joaquin Valley to address issues relating to ozone effects on tree fruit and nut crops, (2) evaluate pollutant exposure systems for trees, (3) conduct a field survey of ozone injury to cotton in the San Joaquin Valley, (4) perform a detailed analysis of crop losses in the San Joaquin Valley, (5) revise all databases and carry out a statewide assessment of the effects of ozone on crop productivity in 1986, and (6) prepare and present information on crop and forest losses in California.

The fruit and nut tree workshop was held on November 16, 1988, at the University of California Kearney Agricultural Center. Twenty individuals attended including an industry representative, USDA staff, University of California scientists, California Air Resources Board staff, and county farm advisors. Many useful recommendations regarding future tree fruit and nut crop research were made.

The tree exposure system evaluation considered 51 designs of field chambers, 18 types of open-air field exposure systems, and ten plans for branch chambers. Ten of these systems were considered in more detail for potential for field studies with trees. Finally, three systems were more critically evaluated and analyzed for cost of construction and operation. The final three systems included a large open-top field chamber, a tubular 'ZAPS' system, and a type of branch chamber.

A total of 48 fields were evaluated as part of the San Joaquin Valley cotton survey. The field survey indicated that many factors {other than air pollution were causing injury to cotton during the late summer of 1988. The only definite ozone injury occurred in Kern county, especially southeast of Bakersfield, and possibly in Tulare county.

The San Joaquin Valley crop loss assessment indicated that losses are reduced by over 50% for most crops grown on the west side compared to the east side of the San Joaquin Valley. Statewide losses for 27 crops were determined using crop productivity and ozone concentration data for 1986. Six crops had losses of greater = 15% (dry beans, cantaloupes, cotton, honeydew melons, grapes, and watermelons). The data for the three types of melon is tentative as the loss equation was based on data for muskmelon collected in Indiana. Seven other crops had losses = 6% (alfalfa hay, alfalfa seed, sweet corn, lemons, oranges, potatoes, and spinach). Eight crops had small losses of 1-3% (field corn, grain sorghum, onion, rice, corn-sflage, fresh tomatoes, processing tomatoes, and wheat). Six crops had no losses (barley, broccoli, celery, lettuce, strawberries, and sugar beets).

Future crop loss from ozone projections were made for 1995 and 2010 based on assumptions regarding possible changes in statewide ozone concentrations. Crop yield losses from ozone were estimated to increase by 8-14% for 2010 compared to 1986 for most crops due to an increase in NO, emissions, a precursor for ozone.

Thus, this project continues to provide a comprehensive understanding of the current status of air pollution effects on California vegetation, a needed synthesis of presently dispersed tree and crop response reports in the literature, models of air pollutant vegetation losses specific to the unique California conditions and an on-line program for field assessment of injury.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

Stay involved, sign up with ARB's Research Email Listserver