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December 30th, 2002 Your questions and answers about everything stream related.
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Q. From John in Colorado...What effects are all of the wildfires in the west likely to have on the ecology of the streams?
A.
A good question, and one that would require more space than
we have here to completely answer. However, there is a good
body of information from the research conducted by Dr. G.W.
Minshall and his colleagues from Idaho State Univerity who have
extensively studied the impact of the 1988 Yellowstone fires on
streams in the Park. I will use his published findings to
provide some insights.
Suspended sediments - initial increase followed by gradual
reduction as watershed reforestation progresses.
Nutrient output - rapid increase during first year followed
by gradual reduction to pre-burn levels after about 10 years.
Incident radiation - increase with destruction of canopy
followed by gradual reduction as forest succession proceeds;
could result in increased water temperatures depending on size
of stream.
Primary production (algal/plant growth) - increase in
headwater streams coincident with increased incident radiation
and proliferation of algae; gradual reduction as forest
succession proceeds.
Litter input - considerable fluctuation as forest develops;
related to delayed input of fire-killed snags, new growth, etc.
Shredders (aquatic insects that feed on leaf or other coarse
organic matter) - initial reduction as inputs of coarse
particulate organic matter from terrestrial landscape are
absent; gradual increase in later years as these inputs are
reestablished as reforestation occurs.
Grazers (aquatic insects that scrape algae from rock surfaces)
- increase after first year coincident with increased incident radiation and
algal growth; decrease as canopy developes and shading is
reestablished.
Collectors (aquatic insects that pick up fine organic matter
from the bottom or filter it from the water column)- gradual increase out
to about 5 years as increased inputs of fine particulate organic matter
from the disturbed surrounding landscape reach the stream; gradual
reduction as watershed becomes more stable.
The 'Stream Doctor' is a retired professional stream ecologist and
author, now living in the West and spending way too much time
fly-fishing. You are invited to submit questions relating to
anything stream related directly to him for use in this Q & A Feature
at streamdoctor@aol.com. |
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