The underside of old growth

The debate about management of old-growth forests near Sisters usually conjures thoughts about soaring big, old trees. Old trees are a big part of "old growth" or "late successional forests," but thousands of other species play important roles in these unique forest habitats.

Under the Northwest Forest Plan, federal land management agencies such as the Forest Service are now required to consider many smaller and less charismatic species than the famed spotted owl.

Old growth forests are believed to link thousands of diverse species. Less flashy plant species such as fungi, lichens, mosses, and liverworts play strong roles in nutrient cycling and tree growth.

Many old-growth-related fungi are "mycorrhizal," forming intricate webs of fungal roots, or "hyphae" that interface with other plants. Their host plants include trees, shrubs, orchids and other wildflowers.

The odd red-and-white striped "Candystick" plant - Allotropa virgata - is found occasionally in old forests near Sisters. It lives in a relationship with mycorrhizal fungi since it has no cholorophyll. Fungi often help supply plants with nitrogen and may help carbon compounds move from tree to tree through underground linkages.

Several very rare underground truffles are found in Sister area old-growth forests. Not all truffles are edible but many have intricate relationships with old trees and rodents. One rare truffle that was found in association with old ponderosa pine near the Metolius River has only been found there and in Italy.

Rodents dig and eat truffles, spreading spores throughout the forest.

Drainages coming off the Cascade Mountains support some unusual lichens more commonly found in the lush, wetter old forests of the westside. Westside lichens sneak over to eastside forests in the moist forests near streams or riparian areas. These plants, which grow on tree trunks, branches and down wood, also help fix nitrogen. Some of our rarest lichens grow on large old black cottonwood trees and other hardwoods.

Old growth forests provide a real biodiversity challenge for forest scientists. Intact old-growth habitats are limited and have changed due to fire suppression, logging, and mortality from drought and insects. Many old-growth-dependent species are not well known, are difficult to identify, and may be hard to find.

Management considerations for these species include protecting known sites, regional surveys, and leaving untouched islands during logging of all types of forests. Old forest structures such as big old trees, big dead trees, snags and down wood, are especially valuable to leave undisturbed.

These legacies from previous forests act as refuges for slow-moving and growing species. From these areas, old-growth-dependent species can slowly spread out and colonize younger forests.