. The Canadian field-naturalist. 1998 Begg, Archibold, and Delanoy: Riparian Cottonwoods 685. Figure 1. General study area and location of the sampling sites. normal because of drying out of the seedbed. In the first year, drought stress due to poorly developed root systems can further increase mortality, but by the end of the second year the root system may be up to 3 meters long (Read 1958). Other methods of regeneration are asexual propogation through root sprouts and coppicing. Both methods were noted on the North and South Saskatchewan rivers. Several studies have shown that damming can i
. The Canadian field-naturalist. 1998 Begg, Archibold, and Delanoy: Riparian Cottonwoods 685. Figure 1. General study area and location of the sampling sites. normal because of drying out of the seedbed. In the first year, drought stress due to poorly developed root systems can further increase mortality, but by the end of the second year the root system may be up to 3 meters long (Read 1958). Other methods of regeneration are asexual propogation through root sprouts and coppicing. Both methods were noted on the North and South Saskatchewan rivers. Several studies have shown that damming can impact riparian ecosystems because the river flows and controlled water levels no longer match the natural regime (Mahoney et al. 1995; Rood and Mahoney 1990). Similarly, sediments carried by spring flood waters are trapped in reservoirs on regu- lated rivers; this affects point bar development and channel migration. Thus, Crouch (1979) noted a decline in cottonwoods along the South Platte River in Colorado; similar declines are reported for the Milk River (Bradley and Smith 1986) and the St. Mary's River (Rood and Heinze-Milne 1989), both located in southern Alberta. High water levels in the spring function to recharge ground water reserves (Hall 1973) which are utilized by the deep roots of the cottonwoods. Without this replenishment there is increased risk of drought-induced mortality of estab- lished trees (Reily and Johnson 1981). In 1968 the Gardiner Dam was closed on the South Saskatchewan River resulting in the forma- tion of Lake Diefenbaker. The purpose of this study is to determine if the damming of the South Saskatchewan River has had an impact on the ripar- ian Cottonwood populations at two sites down- stream from this dam and compares their age-class structure and population recruitment trends with sites on the nearby, relatively unregulated North Saskatchewan Please note that these images are extracted from scanned page images that may have been digitally
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