Sunday, 18 May 2008

Signs of stress

So many eucalypts around here are showing signs of stress because of the long years of lower-than-average rainfall. I see in suburban gardens and streets and on the university campus and initially thought that it may only be the introduced trees, eucalypts from other areas, that were suffering the most. But most local species are also effected - the wonderful Ironbarks in Ironbark Basin at Anglesea, the Yellow Gums at Bannockburn and Inverleigh, River Red Gums along the Barwon River.

What are the signs of stress? One of the first things I notice is that the normally open leaf canopy becomes even more open. The trees start to lose their leaves and do not grow new ones. The top branches start to die. The tree starts to produce leaves on the lower branches. New growth appears from ground level. I wonder what will happen in our local bush areas when the dry conditions continue, as many scientists predict, as a result of climate change.

Diana Snape wrote a great little article in last Saturday's The Age on this subject, called 'They will survive'. She was talking about several trees in her home garden that are shooting from the lignotuber. She writes:

The tree was obviously going into survival mode. (It must be easier to
raise water for photosynthesis just a metre or two rather than up to the
full height of the tree, which is close to six metres.)

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