On 14/08/2014 11:18, Nick Maclaren wrote:
In article , wrote:
Judith in England wrote:

I must admit I was gobsmacked with the comments about the depth of the root
systems: I always thought that the main root system were much deeper than one
or two meters.

If you've ever pulled trees out with a tractor or seen fallen trees
that have pulled up their roots then it's very obvious. The roots on
big trees *spread* but don't go very deep, there's nothing down there
for the tree to 'feed' on.

There are sometimes a few large, deep roots, but only for certain
species of tree under certain conditions. But, as I said, I am
pretty sure that those are only for anchorage and/or getting
water. The available nutrients are, as you say, usually almost
entirely in the top foot or two.

Eucalyptus are usually regarded as fairly shallow-rooted species, but
some species go very deep in search of water (see figs 2 and 3):
http://www.hermonslade.org.au/projec.../hsf_11_1.html

--

Jeff