In the past, an approximate spatial characterization of the risks to California forests from ozone was developed by other investigators using existing forest resource and ozone databases and expert-estimated sensitivities for tree species. Potential impact was the primary product. Others have employed GIS-based risk assessment approaches; however, this approach requires much calibration and evaluation with on-the-ground measurements of mature tree response to ozone. In regard to the measured impacts of ozone on pines in the mixed conifer forest type in the Sierra Nevada and the mountains of southern California, there is a nearly 30-year record of the assessments at specific locations. Within the last 5 years, the assessment of ozone injury to ponderosa (Pinus ponderosa Dougl. ex Laws.) and Jeffrey (P. jeffreyi Grev. & Balf.) pines has been improved by a descriptive procedure called the ozone injury index (OII). This procedure has been used between 1991 and 1994 to assess the condition of ponderosa and/or Jeffrey pines using approximately 50 trees at each of 33 sites throughout the north to south extent of the Sierra Nevada, and including the San Bernardino mountains. Average ozone-caused foliar damage for all 4 years showed an increase from north to south in California. Crown position class had an influence on ozone injury amount; dominant (D) and open grown (OG) trees have generally lower Oils (less injury) than codominant (CD) and intermediate (I) trees. The survey procedure confirmed ozone injury only if the distinctive chlorotic mottle symptom was present. However, the survey also recorded an upper leaf surface necrotic spotting called weather or winter fleck which is seen on needles that have been exposed to at least one winter period. The exact cause of winter Reck is unknown. Survey results show the intensity to be less in regions with relatively little photochemical pollutant exposure than in regions with moderate to high levels of pollutant exposure. The significance of winter fleck could be substantial, since it intensifies with each winter and diminishes the amount of healthy mesophyll tissue available for photosynthesis. Future assessments of the risk of ozone injury to the mixed conifer forest type should incorporate further developments in spatial analysis techniques, and ground truth should be provided by actual mature tree injury information from forest plots.

EcologyVolume 63, Issue 2 p. 598-598 Article Air Pollution and Forests Paul R. Miller, Paul R. MillerSearch for more papers by this author Paul R. Miller, Paul R. MillerSearch for more papers by this author First published: 01 April 1982 https://doi.org/10.2307/1938988Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume63, Issue2April 1982Pages 598-598 RelatedInformation

Hourly ambient ozone exposure data and crown injury measurements were gathered in the Sierra Nevada and San Bernardino Mountains of California to develop relationships between the Ozone Injury Index (OII), the Forest Pest Management Index (FPM), chlorotic mottle, fascicle retention (OII index components) and cumulative ambient ozone indices for Pinus ponderosa Dougl. ex Laws and Pinus jeffreyi Grev. and Balf. Eleven sites located in the mixed conifer forest near ambient ozone monitoring sites were evaluated annually for 4 years. Four other sites in the San Bernardino Mountains were evaluated for 1 year. Analyses showed OII to be functionally equivalent (r2 = 0.96) to the FPM, and to depend only on fascicle retention and chlorotic mottle (R2 = 0.95) of the fourth whorl (or if four whorls are not present at the site, then the last whorl present for the majority of trees). Significant associations were found between OII and 4-year 24-h. summer SUM0, SUM06, W126 and HRS80 ozone indices. Three sites had higher levels of cumulative chlorotic mottle for individual whorls and larger numbers of trees with visible crown injury than other sites with similar cumulative ambient ozone levels. Including an indicator variable to discriminate between these two groups of sites increased R2 and decreased root mean square (RMSE) for all indices, especially SUM0 (R2 = 0.93, RMSE reduced by 46%).