Falling by the wayside

Many consider themselves fortunate to live in an area with four distinct seasons.

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They look forward to the first signs of spring, warm summer breezes, the changing colors of autumn leaves and the first snow of winter.

This year, however, Mother Nature seems to be set on cheating people on the Kenai Peninsula out of their anticipated autumnal palette.

Because the area has experienced an unusually hot summer with very small amounts of rain, deciduous trees such as aspen, birch and cottonwood already have started dropping their leaves, many without changing to the brilliant yellows, oranges and golds of fall.

It's not just the weather or the amount of rain that determines fall colors, but rainfall does have a lot to do with it.

Leaves actually have the carotenoid pigments that produce yellow, orange and brown colors in them all summer, but the dominant chlorophyll, which gives leaves their bright green color, is being produced in such abundance, it masks the yellow and orange.

Trees use sunlight through photosynthesis to turn water from the ground and carbon dioxide from the air into glucose, a kind of sugar. Plants use glucose as food for energy and as a building block for growth.

Chlorophyll is necessary for photosynthesis to occur.

During the growing season, chlorophyll is continually being produced and broken down, making leaves appear green. As days get shorter in autumn, chlorophyll production slows down and eventually stops, and all chlorophyll is destroyed, unmasking the carotenoids.

During winter, there is not enough light or water for photosynthesis to occur and trees live off food they stored during summer.

Because this summer brought little rainfall, the color change will be delayed, but drought conditions bring in another factor: drought stress.

Drought stress causes trees to go into their shutdown mode early for the next growth season, according to Janice Chumley, integrated pest management technician for the University of Alaska Fairbanks Cooperative Extension Office on Kalifornsky Beach Road.

This means trees begin dropping their leaves prematurely, before fall weather conditions arrive.

As measured at the Kenai Municipal Airport, precipitation this summer totaled 0.67 inches in June, 1.15 inches in July and 0.02 inches in August through Aug. 19.

The averages for those months are 1.19 inches, 1.94 inches and 2.68 inches respectively, according to the Western Regional Climate Center.

In addition to not providing enough water for food production, the dry conditions also open the way for greater insect damage as trees are less able to defend themselves from attack.

"This year we've seen a lot of aspen leaf miner, birch leaf miner and also a ton of cottonwood leaf beetle," Chumley said.

"In some areas on the peninsula, a fungus also has been hitting the alders," she said.

Some of the insect attacks skeletonize the leaves, causing them to drop from the trees before they can turn color, Chumley said.

Besides the effects of the amount of daylight and the amount of moisture, color change is affected by temperature, with a succession of warm, sunny days and cool, crisp but not freezing nights yielding the most spectacular color displays.

While conditions this year may not combine to produce an outstanding display, some yellows and golds are beginning to show marking the arrival of fall.

Can snow be far behind?