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E-M:/ TREES IN DANGER



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Enviro-Mich message from anne.woiwode@sfsierra.sierraclub.org
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Mike -- thanks for the suggestion -- this is a quick and dirty start, and I
hope some biologists can weigh in as well. What I am offering here are
examples of trees disappearing from the forest ecosystems of Michigan which,
while not bordering on extinction in most cases, are being devastated by a
variety of practices and the effects of those practices.

First, our forests and those throughout the U.S. have been diminished by the
loss of extirpated species such as the American Chestnut and American Elm.
Both were almost driven to extinction as a result of exotic disease or pests.
The role these trees played in the forested ecosystems of Michigan if very
hard to estimate, and their loss potentially devastating.  For example, the
description of American elm in Peterson's guide to trees and shrubs notes that
the seeds provided food for many critters, including bobwhite, partridge,
ruffed grouse, prairie chicken, gray and fox squirrels and opossom, and some
of these species are attracting concern because of low population levels.

Second, there is a significant amount of concern about the decline of Northern
white cedar, which has been described as the "living dead" in parts of
Michigan.  Here, a very long lived species is virtually incapable of
reproducing in much of its native in Michigan because of the overwhelming
impact of deer.  Deer depend on cedar as winter cover, and also browse the
trees for food in winter. The effect has been creation of virtual park like
settings in most of the cedar swamps of the state, as all branches above the
snowline and within the reach of the deer on its hind legs are gnawed off.
The life expectancy of the cedar means that these individual trees will
continue to live for many years, but the horrifying reality is that virtually
no trees under the age of forty exist in many parts of Michigan.  

Other species that seem to be declining in a number of landscapes include
yellow birch and hemlock.  Again, these are not likely on the verge of
extinction, but the trend toward simplification of forests is effecting these
types of species in particular.  Both tend to like moist sites.  The yellow
birch seems in particular to depend on fallen logs as "nurse logs" to get it
started regenerating.  Where yellow birch are found, their roots will often
line up along what used to be a log, but what is now just a mound.  Management
techniques, including selection cutting, will end up favoring commercially
desirable species at the expense of non-commercial species that are essential
to the forest, but overlooked when management emphasizes only sawlogs and
pulpwood.

In addition, one of the overlooked categories in many lists of species decline
is shrubs, which fall between trees and herbaceous plants.  The Canada yew,
once a very widely distributed shrub found throughout the forests of the
state, has also been extremely adversely effected by the overwhelming deer
population.  Some describe this plant as "deer candy" because it is favored by
the white-tails.  Where Canada yew is still found in decent size patches, the
deer population has been relatively low, either because it is in a relatively
isolated area or, most often, because the area where the yew is found is in
old-growth or near old-growth conditions with little or no edge and a fairly
closed canopy.  Where it grows well, Canada yew will reach five feet high and
cover continous blocks of the forest floor for tens of hundreds of acres.  You
will find in many places now as a chewed off brown twig at about the snowline,
with some of green flat needles below the snowline.  There have requests made
for the DNR to review the status of this species and consider it for listing
on the state's Endangered Species list, but that request was evidently denied
as part of the current revisions of the list. By the way, this yew is closely
related to the Pacific yew which was being wiped out in the west until it was
realized its bark contained a potential cancer fighting chemical.

I hope others can offer additional information.

Anne Woiwode
Sierra Club


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