Re: Eucalyptus Trees.

[AJH <andrew.heggie@dtn.ntl.com>]

On Wed, 31 Jul 2002 16:14:04 -0700, "Graeme Williams"
<graeme@powerlink.co.nz> wrote:

>
>Q1: My first question is in relation to the soil, which any road cutting or
>creek bank will reveal multi layers.  Do eucalypts individually tap
>different soil layers for minerals and nutrients and in  turn share these
>via mixed forest litter which bush fires turn to potash?

Pass
>
>Q2: In the removal of larger trees excluding them from what was a healthy
>forest mix, would the remaining trees be less healthy or slower growing.  Or
>could it affect the ability of the top soils to release their nutrient?

What if the top soils had no more nutrient to release and that all the
utilizable mineral nutrients were locked in the carbon cycle?
>
>Q3: If we clear original sclerophyll forests and replace them with a
>singular eucalypt species, would the soil remain healthy and sustain mono
>forestry?

The soil will only remain healthy if there is sufficient resources
left to sustain the biomass, this will be chiefly water, K and P with
some trace elements, if you export these from the system then they can
only be replaced by importing replacement or mobilising them from
other strata. On top of this you have added problems from erosion of
the growing medium from wind and flood where perhaps continuous cover
was the "natural" methods of maintaining the habitat.

Obviously some systems cannot sustain harvesting at all, we have
ancient and modern examples from the Roman (and Carthagenian?) grain
fields of the Sahara to the dust bowls of the American 30s.

It seems to me that practices we have in UK, which is a benign growing
area, once exported to less temperate areas lead to serious soil and
nutrient loss. I work with management of lowland heaths (a globally
rare habitat), if the nutrient removal and cyclical burning used over
thousands of years were performed elsewhere then desert rather than an
insect rich heath would be the result.

It looks like we still have not learned, in UK we have a straw burning
powered station reputedly lying idle (not to mention a high tech dual
cycle gasification giving up the ghost today) because it could not
secure straw supplies. In fact it appears it did not consider nutrient
recycling and pitched its buying in price for straw off the field at
slightly lower than the cost of replacing the nutrient lost to the
farmer, hence any prudent farmer prefers to plough it back in.

>I have to say that I am uneasy about deteriorating environments being an
>accepted cost to economic development, or resulting from economic activity
>in unsustainable regaions.  To that end I would like to improve my
>understanding of what might be possible or indeed what might be alredy
>happening to restore some of these cleared areas of theAustralian landscape.

IMO this is an external cost of exporting food which is un
sustainable, we must close local nutrient cycles again or expensively
import replacement chemicals. It also distorts the cost of food/lumber
as we workers in the rich western economies find it uneconomic to
compete with these imports when we attempt farm/forest in a
sustainable manner.

Not intending to place any blame just throwing in my 2 cents/pennies
worth.

Doug how about wandering over to GAS-L and discussing lock hoppers
with me? I may not be able to respond for a few days though.

AJH


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