RIVER FLOW EVENTS AND VEGETATION COLONIZATION OF POINT BARS IN IOWA

Vegetation on point bars must be adapted to changing hydrological and geomorphological conditions. Detailed population data are gathered for 106 1 m² quadrats on two point bars on the Cedar River, Iowa, in the year following a major establishment event when a brief steady river stage coincided with the dispersal period for common riparian pioneer species (Salix interior, S. nigra, Populus deltoides) during a drought year. Significant differences were found in the location of seedlings and different forms of sprouts on a gradient of elevation. Most seedlings, mostly Salix interior, established in a very narrow range that produced a band along the edge of the river. While density in this band is in part related to sediment texture, it is clear that the densities found (e.g., > 500 m^-2) must result from dispersal by water to the strand line. Key words: establishment, point bar, riparian, Salix, seedling.]