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April 15, 2005
Is stressed dead?
Today's Australian (pg 6) states that 75 per cent of red gums along the Murray River are either dead, dying or stressed.
Imagine if a journalist ran the story: 75 per cent of Melbournians are either dead, dying or stressed.
The obvious question might be: So what percentage of Melbournians are dying? We know they are all stressed!
A problem for journalist Asa Waahlquist is that not even the scientists at the Murray Darling Basin Commission are making the distinction between stressed and dead. The official surveys that I am familiar with, that have been undertaken since March 2003, have not distinguished between stressed and dead trees.
Incredible, but true.
Posted by jennifer at April 15, 2005 12:48 PM
Comments
Mark Twain visits MDB.
Mark Twain's immortal quip on the exaggerated reports of his death applies equally to reports of dying forests on the Murray. For trees and humans begin the serious business of dying well before middle age but none of us have any intention of departing soon.
The term "old growth forest" refers to a forest where the predominant stems forming the canopy show signs of senescence, i.e., at least 50% show signs that they are dying. And they will continue to exhibit these attributes for another century or two.
And like humans, trees can actually benefit from stress. Drought stress, in particular, prompts trees to shed leaves from lower limbs to concentrate resources in the upper canopy and thereby produce a tall clean trunk.
And while the green movement may not be comfortable with the concept for obvious anthropomorphic parallels, drought stress enables the strong and straight trees to choke off and kill the bent and twisted ones that cannot justify their presence on their own merits. The stress and mortality that is suffered by the weaker stems is primarily produced by their stronger competitors.
The first reaction of a forest in dry weather is for all stems to shed leaves to reduce transpiration. This thinning of the canopy continues until the more vulnerable stems go below their minimum maintenance point and they die. This death will then free up that residual moisture reserve for use by the survivors.
Trees may die but the forest survives, as they have done for millenia, with a thinner and more open canopy until the next flood produces a baby boom of seedlings who must endure crowded classrooms and a high drop-out rate.
And lets not forget that most of the mortality is inflicted on the younger siblings and yes, the children, of the dominant stems by those very same dominant stems. It is what nature does, get used to it.
But, of course, this will never be cool for treeless urban punters. Keep an eye out for the first arts thesis on "vegofascism in rural Australia". Aah haa, I knew there was something suss here. Its "River Red Necks", by gum.
Yours senescently
Ian Mott
Posted by: Ian Mott at April 19, 2005 10:25 AM