Date: Mon, 3 Apr 95 23:18:54 PDT
From: Peter Langston <psl>
Subject: Redwood Reproduction
Forwarded-by: "firstname.lastname@example.org" <email@example.com>
From: firstname.lastname@example.org (Wilma Keppel)
Sustainable-forestry advocate Hans Burkhardt and I had an unsettling
conversation recently. Hans is a well-known orchid grower, and
was explaining to me that plants with double chromosome sets are
physiologically stronger in many ways, but tend to have poor seed
germination. Coast redwoods are hexaploid -- they have three times
as many chromosomes as the giant sequoia, which gives them extra
vigor and disease resistance. They grow faster, have thicker bark,
and are able to sprout from stumps, which the giant sequoias don't
do. But their seed germination rate is extremely low.
The Burkhardt's 70 acres were logged 54 years ago, and are now
covered with growing redwoods, every one of which is a stump sprout.
The pattern of the stumps indicates that all the original trees
probably grew from seeds. Although grown from stumps that were
mostly 800 years old or older, only some of the young trees are
producing seeds, and these seeds appear to be infertile. After
twenty years on the land, the Burkhardts have never seen a seedling.
Hans figures that in the wild, a redwood had somewhere around 1,000
years to reproduce itself -- that is, to produce one replacement
tree. He theorizes that redwood seeds may not be viable until the
tree is several hundred years old, and that cutting the trees may
set the stump sprouts' biological clocks back to zero, even though
the stump itself is ancient. He also pointed out that most of the
redwoods growing today are biologically adapted to conditions of
800 or more years ago.
If it turns out Hans is right, the implications are staggering.
Every cycle of cutting kills some of the trees; what will we do
for replacements if most forests are cut on a cycle too short to
allow redwood fertility? Research has shown subtle genetic differences
between trees only a short distance apart, indicating that our
coastal forests adapt to the microclimate of each site. If we
replant from trees at only a few sites (because they are the only
ones producing fertile seeds), how well will they adapt? What will
happen to the genetic diversity of the species? What if we have to
wait several hundred years to get redwoods from most of the species'
range back into the gene pool? How well will the redwoods adapt to
changing conditions in the meantime?
Pacific Lumber executives are complaining that the fate of thousand-
year-old trees has been up in the air for a whole <gasp!> eight
years. Corporate leaders with mindsets that have trouble dealing
with decades are trying to manage assets with lifespans of centuries.
So far the redwoods, the lumberjacks, the fisheries, the economy,
and the timber companies' bottom lines have all suffered. It's
likely to get worse.
© 1995 Peter Langston