Organization: Penn State University
Date: Fri, 24 Jul 1992 14:45:45 EDT
From: <MEK104@psuvm.psu.edu>  (Mark Kubiske)
Newsgroups: talk.environment
Subject: Re: Soil Building (was: Libertarians & the environment)

in <dAS-!4B@engin.umich.edu> blagdon@engin.umich.edu (Kenneth James Clark)
writes:

>I can think of a large number of the biggest forests in the world where the
>vast majority of the carbon is *not* stored in the vegetation.  Hint: You
>burn part of one of them in your gas tank.

I stand corrected, the ratio of above to below ground carbon is pretty close
to 1 in the temperate zone, somewhat less in the boreal forests and
considerably more in the tropics.  In general, the more productive the
ecosystem, the more carbon is stored in above ground biomass.  Not to
quibble, but fossil fuels are not forests.  Millions of years ago, the
carbon in hydrocarbons were in the form of carbohydrates, but oil, coal and
natural gas are not part of any forest, not by any stretch of the
immagination.

>You need to qualify your statement to read "in any young forest".

Clearly, a young forest does not necessarily grow on young soil.  An
excellent example of this is a bog forest growing on organic soil that was
at one time open water.  Living in Michigan you *must* be familiar with this
type of primary succession.

>...  the biggest amount of organic matter in middle age and old forests is
>in the soil (nope, didn't say old-growth, doesn't have to be old growth to
>be old).

The oldest forests in the world are in the tropics.  Tropical soils contain
very little organic matter because of the rapid rate of decomposition.  You
need to qualify your statement.

What is your definition of 'old-growth'?

>...  a great deal of very old organic material gets buried year after year
>in this process.  This is soil building.

This is *part* of soil building.  Most forest soils also have a mineral
component.  In fact, the bulk of the soil mass across the whole soil profile
is mineral, not organic.  The addition of organic matter releases nutrients
as the organics decompose, and adds structure which increases moisture
holding and aeration.

>The wood you remove provides no nutrients to the soil, however, which slowly
>depletes the soil.  The tree rotting in the woods dumps all its nutrients
>back into the soil.  Since trees produce more nutrients than they get from
>the soil (minerals from sub-soils, carbon from the atmosphere, energy to
>produce cellulose from photosynthesis) If left alone, a forest produces and
>extra amount of soil each year.  ...  Clear-cutting tilts the scale as far
>as possible to the soil depletion side.


Trees don't produce more nutrients than they get from the soil.  Minerals
(inorganic ions commonly called 'nutrients') from subsoils are already in
the soil, trees just bring them back up to the surface.  No added minerals
there.  Carbon is not a plant nutrient in the common usage of the word.  In
any case, plants don't use carbon from the soil.  Energy (solar radiation
converted to chemical energy) is not a nutrient either.  Most "additions" to
the ecosystem in the form of nutrients come from air born particles
deposited by rain.  Plants don't "manufacture" nutrients.

Tree stems don't return very many nutrients to the soil.  Most of this comes
from leaf litter.  Bole harvesting removes very few nutrients from the site
whichcan be compensated for by longer cutting cycles.  But to do this
requires a large enough acreage of timberland so that rotations can be
extended.  Removal of leaf litter is the greatest threat to nutrient
depletion.  A summer crown fire which burns all the foliage removes far more
nutrients than a bole wood harvest does.

Mark.