| effects
of hemlock wooly adelgid and beech bark disease |
Kirk
Johnson |
| Mar
13, 2006 11:21 PST |
The recent forest disturbance question reminds me of something
I've been
meaning to ask. No one wants to see pathogens like the chestnut
blight,
beech bark disease, the hemlock wooly adelgid, etc. sweep
through our
forests. However, I have wondered if anyone has been studying
potential
ecological side benefits to these phenomenon.
For example, up until 5 years ago or so , the Hickory Creek
Wilderness Area
in the Allegheny National Forest was largely a second and
third-growth
even-aged forest with almost a completely closed canopy and a
dearth of
coarse woody debris on the forest floor.
In recent years, however, many beech trees in the wilderness
have died, and
snapped off or tipped over completely. This has created numerous
canopy gaps
that allow more sunlight to reach the forest floor, and it has
also injected
an "instantaneous" coarse woody debris component to
the forest ecosystem.
There are also many standing beech snags.
I would be interested to find out if there is a positive
ecological response
to beech bark disease and hemlock wooly adelgid (homes for
cavity nesters in
the snags, homes for ground-dwelling mammals and others on the
forest floor,
diversifying the fluvial geomorphology in forest streams, etc.).
Is there a
silver lining to be found in all of this? Is anyone specifically
studying
this in any kind of detail? I am particularly interested in the
effects of
the hemlock wooly adelgid.
Thanks in advance for any help.
Kirk Johnson
Warren, PA |
| Re:
effects of hemlock wooly adelgid and beech bark disease |
Lee
E. Frelich |
| Mar
13, 2006 12:56 PST |
Kirk:
A general principle in ecology is that what is bad for one
species (or
suite of species) is good for another species or group of
species.
Something always benefits when new space and resources are made
available. Other species of trees will expand their niche and
fill the gaps.
In this case, these pests and diseases represent a threat to all
remaining
old growth that does not respond to any sort of human
protection, such as
being a designated wilderness area, and old growth is already
rare due to
logging. So from a diversity management point of view they are a
disaster.
Lee
|
| Re:
effects of hemlock wooly adelgid and beech bark disease |
Kirk
Johnson |
| Mar
14, 2006 06:41 PST |
Thanks Lee,
I agree with you that these phenomenon are disasters for
existing old-growth
and I wish none of these non-native pathogens ever found their
way to North
America. If an environmentally benign method could be developed
to
completely exterminate the hemlock wooly adelgid, or somehow
reduce it's
presence to mere background noise, I would personally be
ecstatic.
But anecdotally, watching what's happening in the 2nd and 3rd
growth
even-aged forest of the Hickory Creek Wilderness Area and other
places in
the Allegheny National Forest with beech bark disease, I wonder
if there
aren't subtle benefits occurring too.
For example, could these diseases provide the endangered Indiana
bat with
important new roosting habitat in cavities and under bark
sloughing off dead
hemlock & beech? Also, there is currently little growth in
the HCWA
understory in most places. With the combined effects of the
Pennsylvania
Game Commission working to reduce the state's deer herd, and
beech bark
disease opening gaps in the canopy and allowing more sunlight to
reach the
forest floor, maybe that will help jump-start some important new
growth over
the next several years?
Anyway, just some brain-storming thoughts. I would be interested
to find out
if anyone is studying this sort of thing. Maybe someone's
writing a
dissertation on it somewhere.
Kirk Johnson
|
| Re:
effects of hemlock wooly adelgid and beech bark disease |
adam-@forwild.umass.edu |
| Mar
14, 2006 07:15 PST |
Kirk,
Dave Orwig and myself have been thinking about your very
question quite a bit
over the past few years and are currently working on a
manuscript modeling the
long-term impacts of hemlock woolly adelgid infestations on
coarse woody debris
dynamics in southern New England. I will send you a copy of this
manuscript
once it is completed.
-Tony D'Amato
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