effects of acidity on soil nutrients and tree growth

Mike Pestell pestell at carinehs.wa.edu.au
Thu Nov 28 00:30:57 EST 1996


I am part of an investigation that is trying to establish the cause of tree
deaths in an area of Western Australia. I would be grateful if anyone could
give me data or point me in the direction of publications which could
assist with the folowing points.

I understand that phoshorous is never readily available in soil but is most
available in soils with a pH around 6.5, but that in soils with a pH of 4-5
there can be high concentrations of aluminium, iron and manganese which may
be toxic to the growth of some plants.
In addition the low pH may also result in a shortage of calcium and 
molybdenum and hinder the activities of beneficial microorganisms.
 
I was wondering what the effect of a soil pH of 2.5 would be on the growth
of plants and what levels of metal salts could be found at these pH levels.
There have been some recordings of high levels of chromium and arsenic in
the soils and could these have serios effects on tree growth and if so in
what concentrations.

In particular I was wondering if anyone had information relating to the
effect on Acacia and Eucalypt species.

Finally has anyone come across the phenomenae of recently dead trees
breaking off at the ground and leaving the roots in the ground. The trees
vascular tissue seems to have broken down and this may be linked with the
soil problems discussed above. Is there a likely explanation for the trees
root system maintaining some of its structure whilst the trunk seems to
have decomposed ? 

Any information about the above would be very welcome since the tree deaths
in the area are now reaching into the tens of millions and the problem
seems to be accelerating 

PJ Stanners





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