Hawk, Glenn Martin. 1973. Forest vegetation and soils of terraces and floodplains along the McKenzie River, Oregon. Corvallis, OR: Oregon State University. 188 p. M.S. thesis.
A study of the McKenzie River floodplains, terraces and glacialoutwash plains was undertaken to classify and describe the vegetationand soils of a previously little studied synecological unit.
During the summer of 1971, 54 analytic vegetation and soil
plots (stands) were studied. Cover and frequency of all trees, shrubs,herbs and mosses were recorded as well as a soil description foreach stand. Using Braun-Blanquet manual-visual association tablesand computerized SLMORD analysis, four communities were identified.Further analysis of the four communities revealed two sequences ofseral associes leading to the development of two basic habitat types:one a climatic climax and the other a topo-edaphic climax association.
Succession on floodplains, terraces, and glacial outwash plainsappears initially to follow a change from coarse, shallow soils to fine,deep soils. The climatic climax (Tsuga heterophylla/Acer circinatum/Polystichum munitum-Oxalis oregana association) then develops on
floodplains and terraces with deep, fine textured soils. The topo-edaphic climax (Tsuga heterophylla/Berberis nervosa-Gaultheria shallon/Linnaea borealis association develops on terraces and glacialoutwash plains with shallow, coarse textured soils that have largeamounts of stones and cobbles in all horizons of the soil profile.
Further modifications of sites by fire and flooding also createdifferent plant communities which add to the total diversity of forestvegetation occurring on alluvial deposits of the McKenzie River,Oregon.