- The forest ecosystem is a mosaic of environments, each having a particular set of characteristics and processes that shape the communities of animals and plants that occur there, and circumscribe the opportunities and limitations for land management. In the Cascades of southwestern Washington and northwestern Oregon, environments can be stratified into broad ecological
"zones" based on dominant potential natural vegetation, that reflect macroscale differences in climate (in this area, primarily a function of elevation, topography, and rainshadow effects). On the Gifford Pinchot and Mt. Hood National Forests, six forest zones are recognized: Western Hemlock (lower elevations, west of the Cascade crest and in some riparian areas east of the crest), Pacific Silver Fir (middle elevations on both sides of the Cascades), Mountain Hemlock (upper elevation on both sides), Grand Fir (low to middle elevations east of the Cascade crest in moister sites), Douglas-fir (drier sites east of the crest) and Ponderosa Pine (lowest, driest sites east of the crest).
This publication presents a classification of potential natural vegetation communities, or plant associations, that occur within the Mountain Hemlock Zone on the Gifford Pinchot and Mt. Hood National Forests. These are forests of upper elevations, and include the upper limit of tree growth on major mountain peaks within the area.
Due to the proximity to the Portland-Vancouver metropolitan area, the Mountain Hemlock Zone on both National Forests is expected to provide a both a high level and a wide range of human benefits, including timber production, high quality water, wildlife habitats, recreation opportunities ( especially skiing and backcountry recreation), special forest products such as huckleberries and mushrooms, and more. In addition, the Mountain Hemlock Zone has traditionally been the location within which important Native American activities, such as huckleberry and pinenut gathering, have occurred. Land managers face significant challenges attempting to balance the pressures to continue to meet the expectations of diverse forest users within the context of environmental constraints that exist within the Mountain Hemlock Zone. This Guide attempts to provide a stratification of environments and a discussion of likely management effects in order to help land managers make decisions that fit within the capabilities of individual sites.