On 12/6/95, Ann Camp writes:
> The past week of roundtable discussions has made for interesting and
> stimulating reading. The "hat" I'd like to throw into this arena is the role
> of disturbance in creating and maintaining sustainable ecosystems. There have
> been several messages regarding even-aged vs uneven-aged management, the
> maximum allowable size of gaps (er, clearcuts), and so forth. However,
> different ecosystems developed under different disturbance regimes, and many of
> these ecosystems are characterized by even-aged forests. In some areas,
> even-aged patches are small, and the landscape is more or less uneven-aged
> (Ponderosa pine in the west, for example). In other areas, disturbances were
> catastrophic, and entire landscapes contain trees of similar age.
>
> The biodiversity we all want to protect is a product of an ecosystem's inherent
> disturbance regime. And in many instances, that included disturbance by native
> peoples over thousands of years. Disturbance regimes acted as an environmental
> sieve; what came "out the bottom" is the complement of plants and animals (most
> of which we may be unaware or know little about) that we refer to as
> biodiversity.
>
> If we want to sustain biodiversity within all types of ecosystems, we cannot a
> priori decide that only certain management practices will or won't be
> acceptable. I'll be the first to admit that large industrial clearcuts are 1)
> ugly and 2) don't really mimic a large stand replacing fire (as is so often
> stated). But the aftermath of the Mt. St. Helens eruption wasn't exactly
> aesthetic (fascinating, yes!) and it wasn't the FIRST eruption and the forests
> it destroyed developed under a disturbance regime that included sporadic - very
> sporadic - volcanic eruptions, as well as catastrophic fires and activity by a
> suite of insects and pathogens.
>
> We need to decouple biases against particular sorts of management, and instead
> focus on the types, frequencies, magnitudes of disturbances that generated the
> biodiversity we want to protect. Then, we must couple our management practices
> with extensive monitoring to determine the effects of those practices on
> ecosystem structures and functioning - NOT merely on individual species.
>
> I hope this generates some ideas, controversy, comments.
>
> Ann Camp
Ann,
Thanks for your thought-provoking and informed post. I aggree that
the effects of natural disasters have certainly had an immeasurable
affect on our forest lands. I would like to make two points however.
Natural disasters (volcanoes, fire, etc.) cannot be controlled. Our
human controlled systems of Forest Management can. Thus we may not be
able to stop nature's destruction, but we can certainly stop our own.
One of my biggest concerns with industrial forestry (particulary
clearcutting) is that I don't think enough emphasis is placed on the
long-term viability of the soil. In a forest ecosystem, almost of of the
nutrients are stored in live trees via uptake. Relatively small ammounts
of nutrients are contained in the herbs, weeds, underbrush, or even the
soil itself.
A 1978 study in an experimental forest in New Hampshire found
that the annual uptake rates of nutrients are a small fraction of the
total ammounts in storage. (Likens, et al, 1978) Thus the restoration of
ecosystem nutrients after a clearcut may take several decades, depending,
obviously, on numerous variables. If you also add in the fact that many
forest "management" practices include the spraying of pesticides to
reduce competition, the nutrient replenishment of the soils, and thus
their long-term viability, becomes an important consideration. At least
during natural disasters such as fires and volcanoes, a large portion of
the nutirents are still cycled into the soils. Also, from what I have
read, we are just beginning to understand the importance of the
mycorrhizal fungi and their contributions to forest health. Thus while
clearcutting may be the most economically profitable alternative, I
seriously question it's long term sustainability.
Bret Diamond
Oregon, USA
diam9018@tao.sosc.osshe.edu
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