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  • From: Heide Hermary <heidehermary@pacificcoast.net>
  • To: permaculture@lists.ibiblio.org
  • Subject: Re: [permaculture] "thirsty " trees....
  • Date: Wed, 04 Sep 2002 10:56:34 -0700

Interesting.
I wonder, though, if this is due to the trees being cleared, or the large scale artificial irrigation and use of chemical fertilizers, or maybe a combination of both. I always cringe at simplistic explations that "blame" just one out of many changed variables for the failure of a system. Permaculture is all about understanding systems and relationships. It's all too easy to jump to conclusions...
Heide

permed@nor.com.au wrote:

I have been surprised to read references from Australia blaming the ABSENCE of trees for RAISED ground water levels, because all other references accredit the PRESENCE of trees with raising the water level. I can't pretend to understand the mechanics of either of these assumptions, at least that's what I believe they are.


This phenomena is associated with soil salting in inland areas of Australia. Previous open forest maintained the groundwater levels and more importantly maintained a freshwater layer in the upper ground water. Many of these areas were once part of a large inland sea and the lower groundwaters are quite saline. The forest facilitated the infiltration of fresh rainwater and through transpiration kept water levels down in the flat areas. With the trees cleared groundwater levels under the low rolling hills has dropped and on the flatlands the ground water levels have risen bringing saline water to the surface. Difficult to explain in a nutshell without diagrams but hope this short explanation has helped.
Robyn
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