The Rural Voice, 1998-11, Page 11Scrap Book
How trees can
feed the fish
One way to increase tree cover
in southern Ontario (which is
down to seven per cent) is the
rehabilitation of stream banks,
said Dr. Andrew Gordon,
Professor of Agroforestry and
Forest Ecology at the University
of Guelph. Thousands of acres of
trees could be planted as buffers
along streams and open drains
Gordon said during a recent
Agroforestry tour.
To illustrate the benefits tour
participants were taken to the
Washington Creek environmental
site, part of the Grand River
watershed. Trees in buffer strips
along the banks encourage fish
populations by reducing light
intensity and lowering water
temperature, particularly
important for brook trout.
Experiments at Washington
Creek began in 1985 when the
stream was little more than an
open ditch in a pasture field.
Today the stream is a beautiful,
shaded park -like recreation area
used by members of the Brethren
of Early Christianity communal
farm, which owns the land.
Researcher Maren Oclbermann
has been studying the ongoing
changes in the stream, particularly
the amount of litter fall (leaves,
bark, etc.) entering the stream
from the trees around it. This is
important because when leaves
fall into the water they are eaten
up by insects which in turn
provide food for the fish. She set
traps across the stream to catch
leaves, calculating that four to five
tonnes of litter fell per hectare per
year. But while these leaves
contain nitrogen, nitrate levels in
the water decreased over the years
as the buffer zone filtered nitrogen
from agricultural sources.
But Gordon cautioned that
repairing the damage to streams
must be done on the whole river
system. You can't take a 10 km
stream and plant trees on 1.6 km
of it and expect to change water
quality, he said.0
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