Document: REB-3-65-43

Changes in the distribution and amount of late successional/old growth, hardwood and shrub cover types in the coast range of Oregon, 1939-1993.

HESS, R.S.* ¹ and T.A.SPIES ²

Oregon State University, Corvallis, OR, 97331 ¹
USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR, 97331 ²

Abstract:
Characterizing the shifts over time in the distribution and amount of late successional/old growth, shrub, and hardwood cover types in the Oregon Coast Range is critical for many policy and ecological questions. However, existing estimates of change are based on source data that is too coarse to investigate the pertinent interactions of land use history and environment on vegetation patterns. Our objective was to assess the fine-scale changes in landcover and landcover distribution in the Coast Range of Oregon. We examined landcover across multiple ownerships from 1939 to 1993 using aerial photos and GIS. We delineated and interpreted 1500 20-meter plots for landcover on scanned, georeferenced aerial photos. We compared the distribution of landcover types in 1939 and 1993 to a suite of environmental variables, and to ownership. The number of large and very large conifer and mixed conifer plots declined by 63 percent, from 36% to 13% of all plots, during the 54-year period. Ownership of larger conifer stands shifted from private industrial to federal lands. Shrub and hardwood cover declined by 16 percent, from 31% to 25% of all plots. Shrub and hardwood plots occurred on lower slopes closer to streams in 1993. Younger mixed conifer and pure conifer stands showed the greatest expansion in cover, increasing by 210 percent, from 21% to 44% of all plots. Landowners in the Coast Range have altered the cover and distribution of vegetation in diverse ways, shifting the landscape to one dominated by young conifers, and shifting distribution of hardwood and older coniferous stands toward particular ownerships and site types.

Keywords: late successional/old growth forest, landcover change, hardwoods, shrubs, Oregon Coast Range, multi-ownership landscape

This abstract is being presented at: 11:30 AM in session:
Oral Session #59: Plant Communities: Vegetative Analysis.