U.S.D.A., Forest Service, Region Five, San Francisco, CA
Forest Insect and Disease Management, Report No. 78-1. (1978)
Smog symptoms are common and widespread in much of the southern Sierra Nevada, but the presence of ozone is not currently causing moderate or severe injury to pines on a forest-wide basis. Localized areas with moderately-injured pines do, however, exist, and ozone-sensitive trees will suffer continued injury if past seasonal ozone levels reoccur. Ozone concentrations high enough to produce chlorotic mottle on pines have been measured over a 70-mile portion of the western slopes of the southern Sierra Nevada, but, since 1974, trend plots have not shown any obvious trends in the level of ozone injury. Based on the information from these studies and because of questions still unanswered, the following recommendations are made: 1) conduct a pest damage inventory (PDI) on the Sierra and Sequoia National Forests; 2) continue to monitor ozone levels at selected forest locations, with at least one permanent and continuous monitoring site; 3) establish additional injury trend plots to assess smog effects under a variety of sites, stand characteristics, and ozone concentrations.