Forest and Stream Management in the Oregon Coast Range

Forest and Stream Management in the Oregon Coast Range
Author: Stephen D. Hobbs
Publisher:
Total Pages: 336
Release: 2002
Genre: Nature
ISBN:

This major volume presents a wealth of fundamental and applied research on managing Coast Range forest and stream ecosystems. Written primarily for managers and resource specialists, the book will also appeal to policymakers, resource scientists, forest landowners, the conservation community, and students interested in forestry, fisheries, and wildlife sciences.

Watershed-scale Vegetation Patterns in a Late-successional Forest Landscape in the Oregon Coast Range

Watershed-scale Vegetation Patterns in a Late-successional Forest Landscape in the Oregon Coast Range
Author: Michael C. Wimberly
Publisher:
Total Pages: 356
Release: 1999
Genre: Forest ecology
ISBN:

Knowledge about vegetation patterns and ecological processes in unmanaged, late-successional watersheds is needed to provide a foundation for forest management strategies aimed at conserving native biodiversity. I examined influences of environmental variability and disturbance history on forest structure and composition in the Cummins Creek Wilderness, located on the central Oregon coast. Climatic and topographic variables explained the majority of hillslope community composition, while fire history explained most of the variability in hillslope forest structure. Forest structure and composition in riparian areas was related to a climatic gradient as well as position in the stream network. The abundance of two fire-sensitive species, Tsuga heterophylla (western hemlock) and Picea sitchensis (Sitka spruce), decreased with distance from old-growth patches, possibly reflecting a seed dispersal gradient that occurred following fires 80 to 140 years ago. I developed predictive maps of understory conifer patterns using remote sensing, aerial photographs, digital elevation models and stream maps. I predicted P. sitchensis regeneration based on distance from the coast and topography, and T. heterophylla regeneration based on crown size, percent hardwood composition, topography, and distance from old-growth patches. Although I found statistically significant relationships between understory patterns and GIS predictor variables, the models explained only low to moderate amounts of the overall variability. Landscape-scale simulations of T. heterophylla showed that population expansion through gap-phase recruitment was limited by short seed dispersal distances in closed-canopy forests, the requirement for canopy gap disturbances to facilitate overstory recruitment, and the lag between recruitment and reproduction. Although fine-scale habitat features can influence the amount of regeneration in a gap when seed sources are present, the fire regime may ultimately control the abundance of T. heterophylla at the landscape scale through dispersal limitations. Brief increases in fire frequency can cause a sustained decrease in the amount of T. heterophylla on the landscape once fire frequency is reduced below a threshold value. Our results emphasize the complexity and diversity of forest vegetation at the watershed scale. Environmental variability, disturbance history, and dispersal limitations have all played a role in creating the current landscape patterns in the Cummins Creek Wilderness.

Contextual Systems Description of an Oregon Coastal Watershed

Contextual Systems Description of an Oregon Coastal Watershed
Author: Brigitte Goetze
Publisher:
Total Pages: 348
Release: 1988
Genre: Watershed management
ISBN:

Many resource management controversies indicate disagreement about the possible intended and unintended effects of management actions on ecosystems. Researchers have documented a variety of negative effects on specific ecosystems, e. g. the degradation of salmonid habitat due to mass wasting (Hagans et al. 1986). While the effects of some management actions are reversible, others change systems capacities and are therefore irreversible, e.g. the poisoning of Kesterson Wildlife Refuge with selenium due to agricultural practices (Schuler 1987). The difference between reversible and irreversible management effects is often a matter of scale. Management actions that are out of concordance with the properties of a system have the potential to irreversibly change a system if applied over large spatial and temporal scales. Using the method of contextual watershed classification (Warren 1979) the concordance of forest management with the properties of the Yaquina drainage (an Oregon coastal watershed of 220 sq. mi. size) and its environmental class (the North-central Coast Range) are evaluated. For this purpose, the watershed and its environment are classified according to five components: climate, substrate, biota, water, and culture. Properties are selected that are rather invariant and general, and therefore reflect the potential capacities of system and environment. The climatic, geologic, geomorphic, and hydrologic characteristics are compared to trophic relationships and life history traits of selected tree species in an attempt to understand the biophysical relationships in the forest environment that dominates the watershed. It is found that commonly applied harvest regimes are out of concordance with the biophysical environment and thus have the potential to lead to resource loss. Alternative management practices that would be more concordant with resource properties are proposed. The influence of dominant world views (namely mechanism, realism, rationalism, individualism, utilitarianism, and elitism) on the forest planning process and on the opinions of community leaders is evaluated. It is found that forest management practices, although they are out of concordance with the biophysical environment, are in concordance with the larger cultural environment and the perceptions and opinions of local community leaders. Hence, adopting new practices that are more concordant with the biophysical environment will be difficult. The major hindrance is located in the economic sphere. Concerns relating to the economical sphere are discussed and a probable route to more concordant resource use is proposed.

Debris Flow Characteristics Associated with Forest Practices in the Central Oregon Coast Range

Debris Flow Characteristics Associated with Forest Practices in the Central Oregon Coast Range
Author: Christine L. May
Publisher:
Total Pages: 242
Release: 1998
Genre: Debris avalanches
ISBN:

Debris flows in the Pacific Northwest play a major role in routing wood and sediment stored on hillslopes and in first- through third-order channels to higher order channels and valley floors. Forest practices on steep, unstable slopes and removal of riparian trees along low-order streams can affect the frequency, magnitude, and composition of debris flows. The quantity and quality of debris flow deposits provides sediment and wood fundamental to the development of the receiving channel. Field surveys document characteristics of the initiation site, runout zone, and deposit of 53 debris flows in the Siuslaw Basin of the central Oregon Coast Range, during the winter of 1996. Landslides that initiated debris flows in clearcuts had a higher frequency, larger average volume, and runout zones that affected a greater length of stream channel than landslides from forested slopes. This difference resulted in an increase in the total volume of sediment mobilized by the debris flow, and a greater proportion of this sediment came from hillslope sources. Debris flows initiated at roads had an order of magnitude greater volume of sediment compared to non-road-related failures. Debris flows of equivalent size that traveled through a forested channel delivered only a slightly greater volume of large wood, than those through clearcuts. Size-class distributions of wood in the deposit and trees on the hillslope were not well correlated. The average diameter of wood in the deposit was greater than the diameter of trees currently present on the surrounding hillslopes. This difference reflects the legacy of large woody debris stored in low-order channels and valley floors. Large trees along the edge of the runout zone is also an important component in the recovery of these low-order channels, which were transformed into a bedrock state. Large trees along the edges of forested slopes are already supplying wood to these channels, and were the only mechanism observed for trapping large volumes of sediment. This mechanism for retaining sediment in high gradient, low-roughness channels is not available in clearcuts, which now contain the greatest proportion of bedrock channels. Forest practices, by altering the frequency, magnitude, and composition of the debris flow, may alter the long-term potential for developing complex channel morphology and high-quality aquatic habitat.