Trophic interactions
occurring in headwater forested stream ecosystems are closely
linked to associated riparian communities, and these communities
play a critical role in regulating nutrient and energy flow
in lotic systems. Allochthonous inputs (arthropods, leaf litter,
and wood) entering a stream affect microbial and benthic invertebrate
communities. For instance, leaf inputs are a basic food resource
for microbes and invertebrates in forested headwater stream
systems. In addition, riparian vegetation influences the composition
of associated terrestrial invertebrate assemblages. Together,
aquatic and terrestrial invertebrates form an important prey
base in stream ecosystems for consumers such as predatory fish.
However, knowledge concerning fish and aquatic invertebrate
trophic interactions in relation to inputs (litter and insects)
from riparian communities is lacking in the Pacific Northwest.
Such information is critical to the understanding of terrestrial-aquatic
linkages between riparian communities and stream food webs.
Riparian management activities that alter vegetation regimes may affect food resource availability to terrestrial and aquatic invertebrate communities and salmonids. Because salmonids are declining throughout their historic range, management activities that may reduce persistence need to be carefully examined. Given the potential importance of allochthonous inputs from riparian communities to stream ecosystem dynamics, significant questions remain unresolved:
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How
does prey availability and consumption by coastal cutthroat
trout differ among conifer, deciduous, and mixed riparian
communities? |
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What
is the seasonal variation in diet of cutthroat trout within
and among these riparian communities? |
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To examine these questions, we are comparing
allochthonous inputs from conifer, deciduous, and mixed riparian communities to
assess invertebrate prey abundance and diet of coastal cutthroat trout in three
streams of the Oregon Coast Range. Studies are being initiated to examine invertebrate
abundance, biomass, and composition in benthos and drift and to determine seasonal
variation in diet of cutthroat trout among stream sections dominated by conifer,
deciduous, or mixed vegetation.
For additional information about this research study see
the 2003 CFER
Annual Report. (2.2 MB)
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