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Old-Growth Forests in the N orthem
James R. Habeck
DcparUnent of Botany University of -Montana
Missoula, Montana 59812
202 Natund Areas JmJlrnaH
ABSTRACT: Old-growth forests still remain in significant amounts in the northern Rocky Mountains on federal forest lands; old growlh in private ownership has mostly been destroyed. U.S. Forest Service personnel of the NOJ1hem Region (a USDA Forest Service subdivision encompassing northern Idaho, Montana, and the western Dakotas) arc developing their plans to fulfill the management goals specified by the National Forest Management Act of 1976. Old-growth ecosystems arc being preserved on national forests within wildernesses, road less areas, research natural areas, and other special interest areas. In addition, U.S. Forest Service personnel arc designating special management areas 10 provide habitat for wildlife that requires or prefers old-growth forests. The U.S. Forest Service's efforts in old-growth conservation, from natural area prog;ams to specially designated old-growth management units, arc described for the northern Rockies. The perpetuation of viable popUlations of wildlife species lhal arc dependent on old-growth conditions has become the focal point in developing old- groWtJ1 management plans for federal foresLs located in the northem Rocky Mountains. However, olel-growth forests have their own intrinsic ecological value independent of wildlife considerations and deserve conservation in a system of land allocations that represents the range of ecosystems found in the northern Rockies. Such a system would provide for the long-term needs of planL
useful in generating enthusiasm, but it can detract from the concept that old- growth forests have their own intrinsic value, that is, that the composite of living forms exhibiting mature stages of interaction with each other and their environment should be recognized and accepted as valued pieces of the landscape's total biotic divcrsity. Jones (1984) agrces, stating that "Witll our present knowledge of the old-growth situation, we should probably be maintaining old growth because of ilS importance as a unique ecosystem rather than basing needs on individual species." Old growth on national forcst lands has come under scrutiny because the National Forest Management Act (NFMA) of 1976, Section 6(g), requires forest managers to provide [or biotic diversity. Federal regulations inter~ preting this directive specify that managers are to maintain viable populations of plants and animals, including species that may require or prefer old-growth habitats to complete their life cycles. Old-growth ecosystems were addressed in a symposium at the 1983 Socicty of American Foresters' national convention. At that time Tceguarden (1984) stated that rules and regulations currently in place went beyond the NFMA's statutory language, and he provided an in-depth analysis of the origins of the old-growth/wildlife can troversy.
Below is a gcneral review of the Northern Region's management program for old growth followed by a discussion of several specific efforts that involve the use of special management areas for diversity maintenance.
NORTHERN ROCKY MOUNTAIN FOREST VEGETATION
Vegetation Types a",1 DislrHlution
The northern Rocky Mountains support considerable vegetative diversity, from the moist maritime forest types in north- ern Idaho and northwestern Montana to the montane ai1d subalpine zones typical of the northern Rocieies. The distribution
Volume 8 (3), 1988
of forest vegetation is correlated with complex environmental gradients, with rainfall, slope, aspect, and elevation being most influential (Habeck 1987, Peet 1988). A gcneralized ordering of forest zones follows: Zone '1 ~ cotton- wood (Populus spp.) - dominant in riparian sites; Zone 2 - dry conifer/ woodland types featuring ponderosa pine (Pinus ponderosa) (Figure 1) and limber pine (P. Jlexilis); Zone 3 - montane/ inland maritime zone composed of Douglas-fir (Pseudotsuga menziesii), western larch (Larix occidentalis) (Fig- ure 2), grand fir (Abies grandis), western redcedar (Thuja plicata) (Figure 3), west- ern hemlock (Tsuga heterophylla), west- ern white pine (Pinus monticola) (Figure 4), paper birch (Betula papyriJera), and aspen (Populus tremuloides); and Zone 4 ~ subalpine and timberline zones with subalpine fir (Abies lasiocarpa), spruce (Picea enge/mannii and hybrids of P. engelmannii/P. glauea), whitebark pine (Pinus albicaulis), mountain hemlock (Tsuga mertensiana), lodgepole pine (Pinus contorta), and alpinc lareh (Larix lyallil) (Habeck 1987).
What is Old Growth?
Old-aged stands (more than 200 ycars old) may be formed from any of the conifers listed above. How these "old" trecs might also exist in the old-growth condition is another matter. Northern Region forest planners and others in the Pacific Northwest (Franklin et al. 1981, Franklin and Spies 1984, Whitney 1987) have attempted to detine old growth. At this time no single concept or definition of old growth has been agreed upon; instead, each national forest admin- istration has been creating its own individualized response to the NFMA regulations. Perhaps the reason for this is the difficulty of arriving at a single definition that would apply to the wide range of ecogeographic subdivisions that make up the northern Rockies.
In an effort to provide the Nez Perce and Kootenai national forests with a functional definition and classification of old-growth forests, Pfister (1987) reviewed a number of different usages for the term. Some definitions of old growth
FIGURE 1. Old-growth ponderosa pine (Pinus ponderosa), about 350 years old. Originally maintaincd parklike by low-intensity fires, Douglas-fir (Pseudotsuga menzi- esii) is seen invading the understory. Photograph taken in 1940 near Darby, Montana, Bitterroot National Forest.
Natural Areas Journal 203
FIGURE 2. Fire-generated western larch (Larix occidentalis) stand exhibiting dam- aged and dead snags. Stand age is about 300 years. Invading subalpine fir (Abies lasiocarpa) is seen in the understory. Taken in 1965 at Swan Valley, Montana, Flathead National Forest.
interject structural charactcristics that obviously relate to wildlife requirements; some represent parts of schemes or models of sllccessional vegetation, employing such terms as "climax," "overmature," "terminal stage," and "most tolerant." Another approach suggests only a gcneralized definition with the option of making it morc specific for individual old-growth types. Pfister discovered that i[ the most commonly used old-growth criteria were applied collectively, very few individual stands would actually quali[ y as old growth. His analysis revealed that a [ew features such as diameters and densities
204 Natural Areas Journal
ofliving trees and standing snags, as well as the amount of dead and down material (tons per acre), would provide reliable criteria for defining old growth within the variety of mountJin forest zones on these two national foresL
FIGURE 3. Climax western redcedar (Thuja plicata). about 500 years old, in the vicinity of Ross Creek Scenic Area and Ross Creek Research Natural Area, Kootenai National Forest, Montana. Photograph taken in ] 963.
Douglas-fir groves developed; remnanl' of these, with individual dominants morc than 100 cm in diamctcr, are still present.
The montane zones of northern Idaho and norLhwestern Montana, which experience an inland maritime climate (greater moisture), historically supported climatic climax old-growth forests dominatcd by western reclcedar and western hemlock. These sites burned less often (100- to 200-year intervals), but when fire did oceur they were often of high intensity, destroying much or all of the sland (Habeck 1978, 1985) and creating a patchy mosaic of successional stages. The major seral species in the moist part.;; of the Northern Region are western white
Volume 8 (3), 1988
pine and western larch; magnificent old- growth stands of u1cse species were prescnt at the time of settlement.
Forc8ts of centuries-old trees also occurred within the subalpine zone where fires seldom reached. Amo and Habeck (1972) reported the presence of 500- to 700-year-old alpine larch at timberline in the northern Rockies. Stands of ancient whitebark pine arc present in the same zone. Any definition of old growth must accommodate forest types occupying severe habitats at upper timberline, as well as the limber pine/ponderosa pine outliers in the warm, dry grasslands of eastern Montana.
The onset of modern fire suppression has been equal in importance to logging in altering the abundance of old-growth forests throughout the northern Rockies. A large portion of the original old-aged ponderosa pine and western larch stands in western Montana, having survived logging, have become densely stocked with Douglas-fir, grand fir, or subalpine fir regeneration and are now developing without further fire disturbance toward climax stages dominated by shade- tolerant species. The events and circumstances conducive to generating and maintaining some kinds of old-age forest no longer exist; this is being recognized by forest ecologists developing long-term forest plans.
Natural Areas Journal 205
FIGURE 4. Old-growth seral forest, exceeding 200 years, composed of western white pine (Pinus monticola), western hemlock (Tsuga he/erophyl/a), and grand fir (Abies grandis). Montford Creek Research Natural Area, Coeur d'Alene Nation