Discussion of general forest ecology concepts and of forest management practices.
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Why trees really dump their leaves
Published: 23/10/2010 00:01 - Updated: 22/10/2010 18:54
http://www.cambridge-news.co.uk/Home/Wh ... leaves.htm
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Traditional science has it that leaves fall as temperatures drop during the autumn, allowing the plant to enter a resting phase and save energy. But Prof Brian Ford, a scientist, writer and broadcaster, believes leaf drop occurs in order to excrete waste products from the tree. The president of the Cambridge Society for the Application of Research spoke on the subject at the group’s inaugural lecture at Churchill College this week.
He said: “We have long understood the importance of the leaf as the organ of energy capture, through photosynthesis, and of homeostasis, via transpiration. “But the leaf is also an excretophore – a means of consigning unwanted wastes to the void. This is why plants all drop leaves.” (continued) http://www.cambridge-news.co.uk/Home/Wh ... leaves.htm
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I can speculate, and for you strict scientific people out there, I say "speculate" deliberately, that I saw this purpose for shedding leaves once in a very dramatic way. I had bought two bur oak trees about 6 feet tall. When I planted them they were dormant. They leafed out normally and grew a bit. Then by the middle of July, the leaves turned yellow and dropped off. Nuts, my trees are dying! Not so. They promptly put out a new set of leaves. On one tree these persisted until fall, but the other died. Then, the next year, the surviving tree did the same thing in July--leaves turned yellow and dropped off, and new ones grew. The next year the tree held its leaves through the summer.
Now here is my speculation: the trees had had some kind of soil acting weed killer in their soil, probably applied carelessly at the nursery. The trees were poisoned, but they tried to get rid of it by having it accumulate in their leaves, which they then promptly ejected. In one case the "effort" succeded, in the other the poison was just too much.
The surviving tree, after 9 seasons now, seems to be growing completely normally.