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Abstract
We investigated both the current status of nitrogen fixation in Western Washington forests, and the potential effects of acid rain on this vital process. Even the low concentrations of sulfur dioxide presently found in the Northwest are thought to have an adverse effect on nitrogen fixation by limiting the distribution of the epiphytic nitrogen-fixing lichen,
Lobaria pulmonaria, which is found mainly in deciduous forests. A close relative,
L. oregano, was found to be the major nitrogen fixer in old-growth coniferous forests. It fixes less nitrogen following exposure to sulfuric acid of pH 4 or less. A more serious threat to nitrogen fixation than acid rain is the practice of deliberately suppressing red alder to keep it from competing with Douglas fir. Also,
L. oregano is a late successional species and does not develop in forests where short cutting cycles are practiced.
Parent Publication
Citation
Denison, Robert; Caldwell, Bruce; Bormann, Bernard; Eldred, Lindell; Swanberg, Cynthia; Anderson, Steven. 1976. The effects of acid rain on nitrogen fixation in Western Washington coniferous forests. In: Dochinger, L. S.; Seliga, T. A., eds. Proceedings of the first international symposium on acid precipitation and the forest ecosystem; Gen. Tech. Rep. NE-23. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 933-949
