Download Cohabitants o`fthe Shoreline

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NC- 4351
MPR WFWAR
Stat_
Code: 2.13 Reprints:
by I_ichard R. Buech, Research Wildlife Biologist
USDAForestService, NoahCentral Research Station,
erandRapids, Minnesota
Problem:
3
No
_"
__
Cohabitants o'f the Shoreline
Question:
14rhat do beavers
and
in common?
,
willows
.
have
'
•
Answer." Both Of them prefer to have their
"feet" wet[ _ .
Beavers are semi-aquatic animals, that live on the edges
•of streams and lakes in forested areas. Here's that word
again- they are "riparian animals," that is, they live on the
edge of water. Riparian areas are where willows like to
grow too, becauseriparian areas often provide moist habitats wher e many willow species thrive.
The proximity.of beavers and willows is good for
but not so gooq
although beavers prefer aspen to willow, willow is very
high on their list of preferred foods.
Beavers eat both the leaves and bark of willow,
depending on the season of year and what other foods are
available close to shore. It always seems to get down to
that, doesn't it? ":What else is there to eat (which I might
like better)?"
Willow leaves are nutritious in spring and summer.
However, as the growing season ages, their leaves also
age, By late summer and fall, nutrients that were so attractive to beavers earlier in the growing season retreat to the
root system and beavers look elsewhere for food.
Beavers are well known for cutting down trees and
shrubs for food and for constructing dams, lodges, and
Some kinds of Shrubs that are low on the
.eckled alder, are
• branch is one of
bark first
,: or lodge.
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in color towards the extremities. Like leaves using photosynthesis, green bark uses sunlight, water, and carbon
dioxide tO produce
carbohydrates.
Thus, when beavers eat
thegreen
bark of willow, they get a bonus in additional
carbohydrates (starches and sugars),
Cutting and debar, king woody vegetation requires
,
sharp incisors (front-teeth) and powerful jaws. The front
surface of their incisors is comprised of hard enamel and
the back is softer, so their teeth become chisel-shaped,
defenses against being eaten. Willows add phenolic compounds such as salicin to their tissues, which makes them
taste bad to herbivores.
(Does salicin sound familiar?
Aspirin was first derived from salicylic acid found in willow bark!)
:
Producing chemical defenses means willows are not
being productive
in other ways, so willows invest more in
defending young rather than older shoots from herbivotes. Young willow shoots are more succulent--and
were
BeCause cutting and debarking woody stems wears down
their incisors, the teeth of beaver grow continuously
throughout their life- at the rate of 1- 1 /2inch each month!
Not only are willow leaves and bark nutritious, they
usually grow dose to shore and that is VERY important to
beavers. Beavers are superbly adapted to life in water, but
are c-umbersome when on land. In northern Minnesota
it not for protective chemical compounds--they
would be
very attractive to herbivores.
Most kinds of willows are shrubs rather than trees.
Therein lies a disadvantage. Although willows generally
taste good to beavers, their stems are relatively small. This
means that they are more cumbersome to transport.
Instead of dragging a single large branch, beavers often
durir_g fall, when beavers are cutting trees to refurbish
their lodges and construct food caches, they are vulnerable
to wolf predation. The sound of their teeth cutting.
through Wood is quite loud and helps predators zero in on
their location. Thus, they don't spend a lot of time on
shore at any one time.
One researcher collectedwolf
scats (feces) during fall
over a period Of five years and found beaver hair in 5-30%
of scats. Beavers were more common in wolf scats when
must transport a bundle of shoots in their mouth, which
can be a drag on their efficiency.
In the upper Midwest, some beaver families do not
have willows in their territory and thus must rely on other
kinds of trees and shrubs. In the Great Plains and Arctic,
willow can be essential because it is often the only source
of woody vegetation available to beavers. And, beavers
need woody vegetation to build dams, lodges, and food
caches.
deer and moose populations were low, than when they
Were abundant. So, the closer willows are to water (and
the more deer and moose that are around), the safer it is
for beavers to cut them down.
What's a Willow to do? Willows are a favorite food of
Thus, in some regions, beavers and willows have a
LOT in common; the distribution of willows defines
where beavers can live.
bivores (plant eating animals). When animals nip off their
stems> One way willows respond is to simply grow a new
'not
beavers,
but also
snowshoe
other hershoot,only
from
the stump.
Another
more hares
subtle and
response
of
.
willow , (and many other plants) is to produce chemical
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Befl'erll_OIRE$11S
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Roosevelt
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6
Buying
•
.
into the Vision-
an editorial
.
" Department of Natural Resources Commissioner Allen Garber has a "vision'
for forestry in Mix_eso_a. It is printed on the inside front cover of this issue of
Be_er_.
While there has been mixed reaction to the Commissioner's
vision, we commend him for bringing new life and a differing perspective to the
. discussion of how best to manage the forestlands of this state. '
This vision and the discussion it evokes is the most recent indication of the
interest and concern about forest management, and it makes a point. The way we
think about forests in Minnesota is not static and unchanging. Rather, like forests
themselves, it is dynamic and constantly evolving.
Four main points_emerge from the Commissioner's vision: 1) less reliance on
aspen; 2) increased numbers and longer-lived conifers; 3) more harvesting
through thinnings and selection systems; and 4) production of more saw timber
and higher value products. Betterll_OM31_
has considered some of these issues. In
our last issue we discussed use of aspen and believe that, while considering
reduced dependence on aspen, we should determine how to get the most value
from:the aspen that are harvested. Aspen is more than pulpwood. The other key
points are very relevant and will be considered in future issues of the magazine.
To achieve these management goals, forest managers will need more information. Our experience is limited and examples are but a few years old. Ithas taken
us 40-plus years tOlearn to manage aspen and red pine effectively. The management proposed by the Commissioner is even more complex. It requires a commitment of time and a dedication to acquiring knowledge.
How do we start?One good example occurred this spring. Foresters from priVate industry, the U.S. Forest Service, Minnesota DNR, counties, University of
Minnesota, and private landowners gathered to discuss how best to manage our
northern hardwood resource--maples, basswood, red oak, paper birch, and other
species. These species can be grown for very high value products such as veneer
and lumber. However, with only some exceptions, these species have not been
managed for these high value products. Discussion was lively; the audience's
passion for managing forests in this way was obvious.
As-we listened, however, we questioned if these discussions related to private
landowner goals.Does growing "quality trees" translate to growing the "quality
forests" that will provide the widest range of values and services? There was limited.discussion on birch bark, maple sugar, medicinal plants, balsam boughs and
mushrooms. These are the "special forest products" treasured by many. These
arepr0ducts that the landowner can use personally or sell for added profit and
•"
value---while simultaneously growing the "quality" trees that typically may be
harvested only once in a private woodland owner's lifetime. We would like to see
their management "fit" into the Commissioner's vision.
•
In managing forests we often apply forest management treatments that bring
no income---that are "n0n-commercial." However these management activities-+ criticalfor growing quality trees-- may also enhance, for instance, the growing of
balsam boughs (a multi-million dollar industry in Minnesota!), mushrooms, and
other special products. Instead of viewing them as "non commercial," such management activities may be viewed "commercial" because of these added values.
When the dialogue with the Commissioner
continued on Minnesota Public
Radio the other day and the question was asked of him: "How will we get this
vision started?" His emphatic answer was th'at private landowners will lead the
Way. TheCommissioner
suggested &at these are the woodland owners who have
themost flexibility and control over land management.
They can begin today to
create these forest conditions of the future.
What will it take to convince the private landowner to "buy in" to this vision?
We believe it will be in growing quality forestsand, on the way to growing quality trees, holding in high esteem those many other:values and services of our
woodlands.
..
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