Document: MAR-3-81-2

Effect of extended inundation on Sidalcea nelsoniana, a threatened wetland prairie perennial.

BARTELS, M.R.* and M.V.WILSON

Oregon State University Corvallis OR 97331 USA ¹

Abstract:
Sidalcea nelsoniana is native to wetland prairies of the Willamette Valley, Oregon and is listed as threatened under the Endangered Species Act. Because of extreme habitat loss, the current distribution of S. nelsoniana might not indicate its complete hydrologic requirements. Moreover, proposals by land managers have suggested flooding some sites for an additional six to eight weeks into spring to improve wetland habitat. The purpose of this study was to evaluate the flooding tolerance of S. nelsoniana and to predict the effect of extended inundation on its performance. Rhizome fragments were transplanted into pots exposed to four flooding conditions: Drained soil, saturated soil with no standing water, standing water from mid-November until mid-April, and standing water from mid-November through mid-June. Treatment differences were most notable starting in April. Plants with drained soil died as the spring rains declined. Plants flooded past April died by mid-June. Plants in saturated soils and those flooded until mid-April were the most successful, and did not differ significantly in survival; number, height and cover of leaves; and number and height of flowering stems. These two treatments most closely match conditions found in Willamette Valley wetland prairies, including S. nelsoniana sites. This suggests that the current distribution of S. nelsoniana approximately matches its hydrologic requirements and that flooding a S. nelsoniana site beyond mid-April may harm this protected species.

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This abstract is being presented at: 3:45 PM in session:
Oral Session #33: Plant Demography.