Vogler, D. R. 1982.
U.S.D.A., Forest Service, Pacific Southwest Region, San Francisco, CA 94111.
Forest Pest Management, Report No. 82-18. (1982)
Ozone injury to pines was first discovered in the southern Sierra Nevada in 1970. Symptoms are now widespread on the Sierra and Sequoia National Forests, yet little is known about ozone's effects at present injury levels. To determine whether height growth of young ponderosa pines is related to severity of symptoms, I surveyed five [pine] plantations on the Hume Lake Ranger District of the Sequoia National Forest in 1978. Ozone had been monitored nearby since 1976, and reached the highest levels to date in the year before the survey. Almost one-half of the trees in the plantations had ozone-injury symptoms, and about 15% were injured on second-year needles; symptoms on current-year needles were very rare, however. I examined two ozone injury rating systems, and found that the severity of needle symptoms was unrelated to height growth at present injury levels. Although the pines declined in height growth in 1977 and 1978, the 1976-77 drought, brush competition, and insect injury probably masked whatever effects ozone may have had. At current pollutant levels in the southern Sierra, ozone does not appear to be an overriding concern in young plantations. Since these pines have been exposed to excess ozone for a few years only, the long-term effects of this exposure are still not known.