OREGON STATE UNIVERSITY

'New Forestry' techniques gain another advocate

05/20/1997

CORVALLIS - Another vote for the techniques of "new forestry" has come from some of the least noticed, but fairly important, parts of the forest ecosystem - the lichens and mosses that live on trees.

Two recent studies at Oregon State University have confirmed that the selective thinning and green tree retention often used in new forestry can play a significant role in saving and repopulating lichens and mosses.

This and other research is reiterating how important these "epiphytes" and "bryophytes" are, for everything from soil fertility to animal habitat and Mother Nature's own type of flood control.

"Many flowering plants, shrubs and trees will resprout from roots or seed banks following a clearcut and slash burn," said Bruce McCune, an OSU associate professor of botany. "But epiphytes - the lichens and mosses that live on the trunks and branches of trees - are almost totally destroyed by this type of forestry. And we're finding that many of the species don't come back very fast."

One study just published in the journal Conservation Biology examined how young, even-aged conifer forests can be enhanced by creative thinning, which included leaving a few hardwoods and remnant trees from previous stands.

It concluded that such an approach created focal points for lichen presence and diversity, which could form the basis for "re-seeding" other nearby trees.

A second study considered the effects of green tree retention that is required in President Clinton's forest plans. It found that old growth associated lichens have a very difficult time dispersing into and colonizing young forests, but that isolated remnant trees foster a more rapid recovery.

According to McCune, lichens and bryophytes perform many functions in forest ecosystems that are critically important but too often ignored.

These mosses, lichens, and "liverworts" play a key role in nitrogen fixation, providing this growth-limiting nutrient to many conifer-dominated forests. They provide food and nesting material for many animal species.

And when they grow into thick mats - almost like a giant sponge - such mosses can play a significant role in absorbing water during rainstorms, releasing it slowly and reducing peak stream flows.

"Our research clearly shows that lichens and mosses perform these functions, although not a lot of work has been done to quantify their importance on a landscape level," McCune said. "And I'm sure there are other roles they play in the forest ecosystem that we don't even understand yet."

Aside from the outright loss of these organisms during clearcutting, McCune said he is also concerned about the way some new forestry approaches are now being implemented - although they still are an important step in the right direction.

"Even when green trees are being left behind during harvest, in many cases for mechanical convenience the trees are in one small clump off to the corner of a clearcut," McCune said. "For purposes of lichen survival and recolonization that's not very effective. Leaving trees more geographically dispersed would be far more desirable."

McCune said he would advocate a mix of isolated trees and small clumps, similar to a common pattern of old trees surviving wildfire.

Research is continuing on why old growth-associated lichens are so slow at colonizing young forests, McCune said.