Tracing a family of trees

THE HIDDEN FOREST By Jon R. Luoma Henry Holt 228 pp, $29.95

TO write the life of a forest, where do you begin and end? If you're not careful, you may end up just where you started.

That's not the result with Jon Luoma's "The Hidden Forest: the Biography of an Ecosystem."

The author states that his book is "a story of discovery." It is indeed; it's an account of some of the ecological revelations that have emerged from American forests in recent years.

Luoma, a contributing editor of Audubon magazine, goes to the scientists who study our forests for a living and reports what they've found.

America's oldest, shaggiest, and most commercially valuable forests occur on the wet coasts of the Pacific Northwest. In 1948, the US Forest Service set aside 16,000 acres just west of Eugene, Ore., as the Andrews Experimental Forest. They assigned a small staff of investigators to find out how it operated, in order to improve management of federal timberlands.

As Luoma explains, what these researchers and their successors learned was that reigning crop-based models of timber extraction - models that recommended cutting every tree in a tract, dragging away all the deadwood, and replanting from scratch - were a prescription for long-term decline.

They found, for instance, that lichens that grow only high up in old trees are critical to the transport of nitrogen to soils, and that seedlings can't prosper without help from vast webs of microscopic fungi that colonize their roots. Both lichens and fungi recover slowly from clearcuts, especially when the cuts involve removal of downed logs from the forest floor.

Here was information damaging to Forest Service doctrine concerning the uselessness of old-growth, and part of Luoma's story is political, detailing how policymakers sought to limit the reach of research they had funded.

As the hills were bared, environmentalists began to ask whether public lands were being managed for the public interest. It seemed that all the region's resources - salmon, water, wildlife, even roads and homes huddled under steep slopes - stood to lose when the woods went to market.

The science of "The Hidden Forest" is fascinating, and it hangs together on the strength of its reporting. Read it to get an idea of what's happening around you next time you take a walk in the woods.

*Thomas Palmer is the author of "Landscape With Reptile."