Forestry effects on riparian areas

Past forestry practices were developed and applied at the stream-reach scale. New forestry focuses on a landscape scale to provide wood products while maintaining ecosystem and community processes. The effect of all forestry practices (e.g., logging, road building, planting, thinning, and slash) on the riparian areas is considered since these areas are part of the landscape. In new forestry, more effort is directed in the planning effort to define site objectives and to understand the implications of each site objective at the landscape scale. This planning provides management with greater flexibility in applying forestry practices to all areas of the landscape as well as in the riparian areas. New forestry is implemented by using the different forestry practices to finesse the stream-reach scale to meet the established objectives in terms of the functional relationship at the landscape scale. FOREST RIPARIAN HABITATS Logging and other forestry-related activities have profound influences on riparian areas and streams How important these riparian systems are with respect to the total forest can be summarized in terms of plant diversity, wildlife habitat, developed recreation, and lumber yield (Figure 1). The example describes the relative importance of riparian areas as natural resources that are typical for a forest on the western slopes of the Cascade Range. The potential for lumber yield is less in riparian areas when compared to good, mesic upland sites due to saturated soils late into the growing season or cobbly soils that tend to be overdrained. An acceptable functional definition for riparian areas was presented in the paper by Hawkins.' Many of the functional relationships associated with riparian areas extend well beyond what would be considered a "normal" riparian-area boundary and up the hillslope. If the concept is to manage by objectives, then practical boundaries must encompass elements of the upland, e.g., the sources for coarse woody debris input to the stream. 'See Hawkins, this volume, page 3. Functional links exist among upland elements, the riparian area, and the channel Often these links between forest riparian vegetation and channel elements are illustrated in the context of an aquatic organism-centered model (Figure 2). Structural links also exist. Some of the attributes of a forest riparian area include diversity in physical structure that results in a richness of biological species. The vertical and horizontal diversity of physical structures provides an abundance of edges. These differences can be illustrated by comparison of narrow, deeply incised channels to wide valley channels with significant floodplains. The frequency of the disturbance regime in a wide valley contributes to the vertical and horizontal heterogeneity. Tree-stand ages differ markedly between riparian areas developed on contrasting geomorphic surfaces. Valley landforms influence stream ecosystems by providing a variety of physical substrates to produce riparian vegetation diversity, a longitudinal spatial distribution, and complex strata of riparian vegetation. Disturbance regimes associated with stream/riparian systems tend to be linear: upstream disturbance influences downstream structure and function. Thus we need to have a basinwide, rather than simply a stream-reach, perspective when considering the management of riparian areas.