Habitat relations of Corydalis aquae-gelidae, a rare riparian plant
Goldenberg, Douglas M.
Zobel, Donald B.
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The relationships between the environment and the abundance of Corydalis aquae-gelidae, an herbaceous perennial and a USFWS species of concern, were explored. Information concerning habitat relations was pursued to determine possible conservation measures. Corydalis grows in headwater streams, up to 1300 m elevation, and down to 585 m on the fifth order Clackamas River, Mt. Hood National Forest, Oregon. Occupied streams had smaller seasonal flow fluctuations than streams where the species was absent, and had summer air and substrate temperatures averaging 17.7 C and 10.6 C, respectively. Corydalis abundance in plots was related to the distance to the summer water level, substrate texture and organic matter content, and plant community composition. Optimal conditions were identified: coarse, moss-covered, mineral substrates within 15 cm of the summer water level. Fine (<2 mm) or organic substrate material reduced Corydalis abundance. On the Oak Grove Fork, about 75% of the plantsgrew between the average winter high and summer low water level, an estimated vertical distance of 25 cm. The results were useful for management, and underscored the need to maintain stable hydrological conditions, avoid sedimentation, and protect riparian areas