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SS3.21 Deconstructing Rivers: The
Ecological, Geomorphic, and Social Consequences of Dam Removal -
Vegetation Colonization of an Exposed Reservoir Bottom
June 13, 2002
ASLO - American Society of Limnology and
Oceanography
Location: Colwood
Shafroth, P, B, USGS Midcontinent Ecological
Science Center, Fort Collins, USA, Pat_Shafroth@usgs.gov
Scott, M, L, USGS Midcontinent Ecological
Science Center, Fort Collins, USA, Mike_L_Scott@usgs.gov
Auble, G, T, USGS Midcontinent Ecological
Science Center, Fort Collins, USA, Greg_Auble@usgs.gov
Following dam removal, the vegetation that
becomes established on the former reservoir bottom influences sediment
transport downstream and site quality for use by humans and wildlife.
Further, the bare substrates characteristic of
exposed reservoir bottoms are at risk of being colonized by
undesirable, exotic species.
We studied vegetation establishment on the
exposed bottom of Horsetooth Reservoir near Fort Collins, Colorado.
Between January 2000 and October 2001, the water
level was drawn down 32 m to enable dam repairs, exposing >550
hectares of substrate.
Water levels are expected to remain low until
early 2004.
In September 2001, we measured the percent cover
of all vascular plant species in 1516, 1 m2 quadrats along fourteen
transects extending from the water's edge to the upland.
We measured the elevation and substrate particle
size distribution of each quadrat.
We recorded >110 species, the most frequent
of which were Chenopodium glaucum (45% frequency) and Panicum
capillare (43% frequency).
We relate the composition and distribution of
plant species to the timing of draw down, elevation above the
reservoir surface, and substrate particle size.
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