permaculture

["Scott Hitchins" <ScottH@wcig.org.au>]

Perhaps the birch trees are not a problem, but a symptom of human 
interference by digging drains: block the drains and the birch trees would 
not be able to establish themselves and the present ones would rot away.  
Peat bogs were often treed areas in the past until watertables rose.
Regards,
Scott Hitchins  

-----Original Message-----
From: Ute Bohnsack [mailto:sustag@eircom.net]
Sent: Monday, 9 September 2002 6:32 PM
To: permaculture@lists.ibiblio.org
Subject: Re: [permaculture] "thirsty " trees....


Dear all,
I haven't followed this thread closely, so accept my apologies if I
write something that has been mentioned before.
There are situations where trees are undesirable because of their
'pumping' action. Raised bogs (peatlands) in Europe would be such an
example. Many raised bogs in e.g. Germany, Netherlands, Scotland,
Ireland have been negatively impacted on by drainage, often at the
margins (with encroaching development, intensification of farming
practices, peat extraction for fuel or horticulture). The slightly drier
conditions resulting from this drainage favour the establishment of
(typically) birch trees which are opportunists when it comes to water
supply. This means that they can deal with dry conditions but if water
is abundant they 'pump' and dry out the bog even more. Restoration
measures for such peatlands include the removal of the birch trees and
the blocking of drains. Now, this is a situation found in a cool,
temperate climate with relatively high rainfall.
There are also situations where non-native trees can cause damage, such
as eucalyptus plantations in arid regions where they compete with native
vegetation for water.
I guess one has to try and get quite detailed information on the local
ecology and ecosystems and/or observe natural ecosystems well, before
one can judge whether certain trees are beneficial or not in a given
situation.

My 2 Euro worth.
Cheers,
Ute 

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