Plant Succession in Temporary Ponds of the Willamette Valley, Oregon

Abstract

The vegetation and factors influencing successionand periodicity in temporary ponds of the Willamette Valley flood plain were studied during 1955-1956 by means of ten transects and eleven quadrats at one temporary pond (railroad), and observational studies at more than 40 temporary ponds. The vegetation of these ponds is characterized by species which occur repeatedly in wet places in the Willamette Valley. Cat-tail (Typha latifolia) and the creeping spike rush (Eleocharis palustris) are the conspicuous plants of temporary ponds in this area. The Submerged Floating stage of temporary ponds contained fewer species of aquatic plants than are usual in Willamette Valley permanent ponds. This reduction in number of species may be the result of the short time that water is present, higher temperatures of shallow water, fluctuating water levels, or changes in the soil caused by the annual drying. The Reed Swamp stage is characterized by the abundant and widespread stands of the cat-tail (Typha latifolia). Marsh speedwell (Veronica scutellata) and water purslane (Ludwigia palustris) are common. Transect data through the reed swamp at the railroad pond show a comparatively high density (4.06 plants per meter). The creeping spike rush (Eleocharis palustris) accounted for almost half of the individual plants in the Sedge Meadow. Transect data showed the Sedge Meadow to have more plants per meter (7.11) than any other stage. Three deciduous trees, cottonwood (Populus trichocarpa), the Oregon ash (Fraxinus oregana) and several species of willow (Salix spp.), appear frequently in the wet margins of the temporary ponds. The tufted hair grass (Deschampsia caespitosa), redtop (Agrostis alba), and velvet grass (Holcus lanatus) have the highest frequencies in the Grassland-Composite stage. The Dried Bed stage includes several species which remain from the submerged-floating stage (Ludwigia palustris, Eleocharis acicularis and Paspalum distichum). Shallower pond beds have a flora different from that of the dried beds of deeper temporary ponds; characteristic species are Grindelia nana, Eryngium petiolatum and Carex unilateralis. Species common to the later-drying deeper ponds are Ludwigia palustris, Eleocharis acicularis and Alisma plantago-aquatica. The flora of other temporary ponds includes many species not found at the railroad pond but all ponds are characterized by the plants mentioned.