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VEGETATION CHARACTERIZATION OF THREE CONTRASTING RIPARIAN SITES, WILLAMETTE VALLEY, OR
Citation:
McAllister, L. S., K. A. Dwire, AND S. M. Griffith. VEGETATION CHARACTERIZATION OF THREE CONTRASTING RIPARIAN SITES, WILLAMETTE VALLEY, OR. International Conference on Riparian Ecology & Management in Multi-land Use Watersheds, Portland, OR, August 28-31, 2000. Wigington, PJ; Beschta, RL (ed.), American Water Resources Association, Middleburg, VA, EPA/600/A-00/020 (NTIS PB2000-107427), 2000.
Description:
Much of the native riparian vegetation of the Willamette Valley, Oregon, has been replaced with agricultural crops or invasive non-native plant species. Detailed information about current Willamette Valley riparian vegetation is generally lacking. Plant species composition data are useful in a variety of applications, including condition assessment, environmental monitoring, and restoration planning. The objective of this study was to characterize the vegetation of three contrasting riparian sites occurring in the Willamette Valley. We determined plant species composition and abundance at a non-cultivated herbaceous site and a cultivated site, both located along Lake Creek, an intermittent stream, and at a forested site located along the Calapooia River, a perennial stream. All sites were adjacent to intensively-managed perennial ryegrass seed production fields. Crop agriculture strongly encroaches on the Lake Creek sites, whereas the Calapooia site had received little encroachment from agriculture beyond the forest edge. Seasonal flooding via a system of backwater sloughs made the forested site less suitable for agricultural conversion. At Lake Creek, we inventoried 32 species at the non-cultivated herbaceous site and 18 species at the cultivated site, most of which were non-native. The cultivated site was dominated by wetland-adapted species in the area closest to the creak where perennial ryegrass was absent. Approximately half of the species at the non-cultivated herbaceous site were facultative upland or upland species, and the site was dominated by introduced pasture grasses. In contrast, the 53 species inventoried at the forested site were mostly native and wetland-adapted. The forested site was dominated by Populus balsamifera ssp. trichocarpa T. & G., Pseudotsuga menziessii (Mirbel) Franco, and Acer macrophyllum Pursh, with extensive shrub and herbaceous strata. Results show a range of vegetative conditions found in riparian areas of the Willam