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Tiffany Woods
The Captial Press Newspaper, April, 19, 2002
Oregon City, Ore. - What
do you do with out-of-control Christmas trees that are too big to
be harvested? "One option is to sell the property," said
woodland manager Gilbert Shibley.
Because not everyone wants to take such a drastic step, he also
suggested owners convert the trees into a forest for timber production.
But it is not as easy as thinning a few trees and then doing nothing
for the next 40 years, said Shibley, who lives on a tree farm near
Estacada, OR.
Thinning too quickly can shock the trees and make them vulnerable
to sunburns, wildfires and wind, he said. First, however, you have
to decide if the soil is adequate and if the trees are healthy.
Ideally, they should come from a local seed source, he told a class
at the Tree School Seminar at Clackamas Community College on April
6.
Tree farmers typically plant 1,500 Christmas trees
per acre, but forests should have only 300 to 500 trees per acre
because they need more light, water and nutrients, said Shibley,
who works part-time for Oregon State University.
"Get those 1,500 ex-Christmas trees down
to 500 or less by age 15 if possible," he said. As a rule of
thumb for spacing, measure the trees' average diameter at breast
height in inches and add four to it, he said. That tells you how
many feet should be between each tree. For example, an 8-inch diameter
plus 4 means that the trees should be spaced every 12 feet. Shibley's
calculations are for Douglas firs.
He described several conversion schedules. If
you start thinning when the trees are 10 years old, you should cut
every third row, leaving 1,000 trees. Then when they are 15 years
old, select out the worst third. Do the same at years 19 and 22
so that you end up with 297 trees, he said.
Amore aggressive option is to cut every third
row and the third worst in the remaining rows at year 10, leaving
667 trees, he said. Then at year 15 select out the worst third and
in year 20 thin the worst half to finish with 224 trees remaining,
he said.
If you get a late start and begin thinning when
the trees are 15 years old, Shibley recommended cutting every third
row, leaving 1,000 trees. Then when they are 18 years old, remove
the worst third. Four years later, remove the worst half and do
that again when the trees are 27 years old, to wind up with 167
trees, he said.
A quicker approach is to cut every third row and
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While you wait, you can sell some of the
thinned trees.
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the worst 33 percent to 50 percent of the remaining
rows when the trees are 15 years old. Then at 20 years old, remove
the worst half of the remaining trees, leaving you with 250 to 333
trees.
A last-ditch effort would be to start thinning
the trees at 20 years old, he said, cutting every second row. Three
years later, select out the worst third. Finally, when the trees
are 26 years old, thin the worst half, leaving 250 trees.
Amore aggressive approach is to cull every third row and the worst
remaining half at year 20 so that you have 500 trees standing. When
they are 24 years old, thin the worst third and repeat at year 28,
leaving 224 trees, he said.
Shibley said the schedules can be modified to
fit an individual's goals. But one thing to keep in mind is to make
sure that the top approximately 40 percent of a tree stays green,
he said.
Trees are ready to be harvested for saw logs when
they are 9 inches to 10 inches in diameter at breast height, he
said.
Turning to the economics of producing Douglas
fir for timber, Shibley said, "It's reasonable to think you
can earn as much per acre per year with forestry as with Christmas
trees. The difference is you have to wait 20 years."
The good news is that while you wait, you
can sell some of the thinned trees, he said. By year 20 to 25, a
thinning can return $800 to $1,600 per acre, he said. When the trees
are 70 years old, an acre can net $20,000 to $24,000, he said. That
figure includes profits from thinnings at 10-year intervals, he
said. Averaged over the long term, a 70-year rotation would net
up to about $350 per acre annually, he said. His estimates were
based on log prices of $600 to $700 per 1,000 board feet.
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