9505 - Laserfiche WebLink

Home Browse Search

Vegetation Vegetation in the study area was analyzed to determine which communities were present that periodically supported standing water. Four major communities regularly have standing water and were sampled in this study. In general the vegetation of the study area is complex based upon river migration patterns. Recent sand bars are colonized by Fremont cottonwood and salt cedar, and large expanses of these woody plants occur. However, these stands are rarely flooded. 1). Open water-aquatic vegetation occurs in several ox-bows and created ponds in the study area. This vegetation was studied to determine the productivity of ox-bow ponds and other wetlands that could be created or restored for fish habitat. The vegetation is dominated by dense stands of Potamogeton pectinatus and occur in water that is up to 4 feet deep. The stands can be so thick that they stratify the water column, creating a warmer, more oxygen rich zone above, and a cold, dark and oxygen poor environment below. This was most pronounced at station 10 where the water beneath the vegetation mat was .anoxic at certain times. 2). Bulrush marshes. Bulrush (Schoenoplectus lacustris) dominated the more shallow margins of ponds and shallow marshes. The stands are very productive with large standing crops. 3). River backwaters. River backwaters occur in several locations in the study area. They all functioned as river channels during high flows which did not carry water at lower flows. Water from the River backs into these areas during low flows forming relatively calm pools that can be quite large. 4). River channel. The river channel served as our control. All samples were compared with the river to determine if invertebrate standing crop was higher or lower in the river.' Very well-developed stands of Fremont cottonwood and salt cedar occur throughout the study area. Cottonwoods are particularly abundant in the recently abandoned channel ,areas and the trees there are relatively young. 28