scholarly journals Impact of rock uplift on rates of late Cenozoic Rocky Mountain river incision

2007 ◽  
Vol 112 (F3) ◽  
Author(s):  
Catherine A. Riihimaki ◽  
Robert S. Anderson ◽  
Elizabeth B. Safran
Keyword(s):  
Rocky Mountain ◽  
Mountain River ◽  
Late Cenozoic ◽  
River Incision

Ecology and coexistence of two species of Brachycentrus (Trichoptera) in a Rocky Mountain river

1986 ◽  
Vol 64 (7) ◽  
pp. 1469-1474 ◽  
Author(s):  
F. Richard Hauer ◽  
Jack A. Stanford
Keyword(s):  
Rocky Mountain ◽  
Late Summer ◽  
Growth Patterns ◽  
Mountain River ◽  
Spring Runoff ◽  
Winter Conditions ◽  
First Instar ◽  
Spring Freshet ◽  
Early Instar ◽  
Peak Runoff

Life-cycle dynamics, growth rates, and relative abundance of Brachycentrus occidentalis and Brachycentrus americanus were studied over a 3-year period in the Flathead River, Montana. Brachycentrus occidentalis appeared as early instar larvae in mid to late summer, grew rapidly during autumn, and reached fourth and fifth instars prior to winter conditions. Most larvae remained active until mid-spring and the onset of spring runoff. Individuals pupated during late April through May and adults emerged after peak runoff in mid-June. Brachycentrus americanus larvae appeared as first instar larvae in autumn and overwintered as early instars. Larvae grew rapidly during spring as temperatures began to rise, but growth was discontinued during spring runoff. Larvae completed growth during summer after the runoff period and emerged in late August and early September. Growth patterns and emergence of both species occurred primarily during fall or spring and late summer, with little growth during winter or spring freshet. Thus growth was associated with quantitatively similar but temporally different periods of organic seston, temperature, and moderate flow.

Microdistributions of filter-feeding caddisflies (Insecta: Trichoptera) in a regulated Rocky Mountain river

1996 ◽  
Vol 74 (4) ◽  
pp. 654-666 ◽  
Author(s):  
Neal J. Voelz ◽  
J. V. Ward
Keyword(s):  
Environmental Gradient ◽  
Rocky Mountain ◽  
Distribution Patterns ◽  
Longitudinal Distribution ◽  
Rock Surface ◽  
Mountain River ◽  
Filter Feeding ◽  
Significant Relationships ◽  
Regulated Stream ◽  
Selection Of

A year-round study was conducted in the Blue River, Colorado, U.S.A., to examine microdistributions of the filter-feeding caddisflies Arctopsyche grandis and Brachycentrus occidentalis along a regulated stream environmental gradient. There was a well-defined longitudinal species replacement, with A. grandis reaching maximum densities 2.3 km below the impoundment and declining downstream as B. occidentalis increased. Arctopsyche grandis was often the only caddisfly found near the dam. The two species co-occurred at two downstream sites, with A. grandis numerically dominant 5.2 km below the impoundment and B. occidentalis at the farthest downstream site (11 km). Near the dam, where densities of filter-feeders were highest, there were significant relationships between individual rock surface area and the number of larvae during most sampling periods. Contrary to our predictions of selection of current-exposed microhabitats, both species occurred primarily on the bottom and lower lateral sides of rocks at all sites. Clumped distribution patterns in the absence of spatial segregation by size class suggests common microhabitat preferenda for species and instars. This use of similar spaces indicates that competitive displacement may occur, partially explaining the longitudinal distribution patterns. At a macroscale the reservoir-induced environmental alterations clearly limit the distribution of organisms, especially at sites directly below the impoundment. As the stream regains its preimpoundment character farther downstream, factors at a microscale may play a more important role in producing the distinct longitudinal distribution patterns.

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