The effects of acid rain on nitrogen fixation in Western Washington coniferous forests

✍ Scribed by Robert Denison; Bruce Caldwell; Bernard Bormann; Lindell Eldred; Cynthia Swanberg; Steven Anderson

• Publisher: Springer Netherlands
• Year: 1977
• Tongue: English
• Weight: 695 KB
• Volume: 8
• Category: Article
• ISSN: 0049-6979
• DOI: 10.1007/bf00156721

✦ Synopsis

We investigated both the current status of N 2 fixation in western Washington forests, and the potential effects of acid rain on this vital process.

Even the low concentrations of SO 2 presently found in the Northwest are thought to have an adverse effect on N2 fixation by limiting the distribution of the epiphytic N2-fixing lichen, Lobaria pulmonaria, which is found mainly in deciduous forests. A close relative, L. oregana, was found to be the major N 2 fixer in old-growth coniferous forests. It fixes less N 2 following exposure to H2SO 4 of pH 4 or less.

A more serious threat to N 2 fixation than acid rain is the practice of deliberately suppressing red alder to keep it from competing with Douglas fir. Also, L. oregana is a late successional species and does not develop in forests where short cutting cycles are practiced.