Extent of oxidant air pollution damage to some pines and other conifers in California.

The incidence of oxidant air pollution damage was investigated on 16 native conifer species in California during a 3-year period. The most serious damage was to Pinus ponderosa, P. jeffreyi, P. coulteri, P. radiata, and Pseudotsuga macrocarpa in the south coast and adjoining portions of the southeast desert air basins including the Angeles, San Bernardino and Cleveland National Forests. P. attenuata was slightly affected in the south coast basin. Suspected oxidant injury symptoms were observed on P. contorta, P. lambertiana, P. torreyana, Abies concolor, and Libocedrus decurrens. No injury was observed on P. sabiniana, P. monophylla, Juniperus occidentalis, Sequoia gigantea and S. sempervirens. Choose-and-cut Christmas tree farms, utilizing mostly P. radiata, have experienced significant oxidant injury during the period of these observations. The potential for new, severe forest damage is located in the mixed conifer forests bordering the east side of the San Joaquin Valley air basin and also in scattered stands in the San Francisco Bay and north central coast air basins. 10 references, 1 figure, 1 table.