Some leaves have already changed colour in N.B.

A8

Charles Perry
Weather

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With almost two weeks still left in August, New Brunswickers are already reporting leaves changing colour and some even falling from the trees.

It is not their imagination; it is occurring, says Dr. Rob Ireland, professor of biology at Mount Allison University.

Ireland said the change of colour in leaves can sometimes take place earlier than normal if certain factors are in place. In this case, he said the factors are a combination of the cooler nights and stress from the steady rainfall this summer.

Trees have a biological clock that is always "ticking away," he explained.

A drop in the temperature during the evenings signifies the fall has arrived and the leaves begin divesting themselves of chlorophyll, said Ireland. He said the chlorophyll accounts for the leaves' green colour, covering up the reds and other colours, below.

The process, which ends with the leaves decaying and dropping to the ground, sees the chlorophyll absorbed into the twigs and the rest of the tree to be stored for next spring, said Ireland.

The tree produces a hormone breaking down the chlorophyll into small molecules allowing it to be stored, said the Mt. A. professor. "The tree has to divest itself of its leaves or they would drag down its branches," he said.

However, if a few unseasonably cool evenings should occur in August, as they have recently, then the tree's biological clock become unbalanced, he said, and the leaves start changing colour earlier than normal.

Ireland said the reverse can occur with the biological clock in the fall if there is some unusually mild weather. He said the clock becomes unbalanced the other way, so that the process of the leaves changing colours is "slowed down" and lasts longer into the autumn than normal.

The other major factor affecting the trees this summer would be the long period of rainy weather the last few weeks, said the biology professor.

Trees are affected by stress, especially diseased ones, said Ireland. He said a few trees would respond well to all the extra rain, but for others, the stress would cause damage and even water-log problems.

And the stress can further trigger leaves changing colour and even falling, said the Mt. A. professor. In some cases, he said, you may notice the leaves have changed colour in only one area of the tree, with the rest of the tree being green.

He said this indicates the part of the tree affected might be damaged or diseased and therefore, more susceptible to the additional stress from all the rain.

Meanwhile, cloudy weather with sunny periods is forecast for today for Metro Moncton. This will be followed by three sunny, mild days (tomorrow, Friday and Saturday), which will see the temperatures shoot up to highs of 25, 29 and 30C (77, 84 and 86F), respectively.

n Charles Perry's Weather appears daily.