Tuesday, September 13, 2011

Natural History: The Season’s First Frost

It is inevitable. Regardless of how nice the summer has been, a time comes in September when the first frost of the season coats every exposed surface with a layer of ice crystals and brings about the official end of the growing season.

While this event causes gardeners to panic about harvesting nearly ripened vegetables, and homeowners to cover up, or bring in their delicate flowering plants, it also brings about the demise of the many forms of life that are unable to tolerate freezing conditions. While there are numerous living entities in our region that can’t survive temperatures below 32 degrees, most are capable, after developing special adaptations that allow them to deal with the changes that are soon to come.

Numerous insects and bugs, along with our annual plants, have evolved to quickly develop from an egg, or seed, in the final days of spring after the threat of a late frost has passed, and take advantage of the favorable conditions that exist over the next three month. These organisms cram their entire lives into the relatively short summer season , but for many lower life forms, a life span of three months is considered to be quite lengthy. Following the Labor Day Weekend, the arrival of freezing conditions, and death is expected, as the populations of most seasonal organisms have already declined greatly, or have completely vanished.

In order to continue to function in an environment in which the temperatures may periodically drop below freezing, many invertebrates, as well as some salamanders, frogs and snakes, develop fatty compounds in their body that act like an antifreeze . While such late season changes to their body chemistry extends the time in which they can remain active, the presence of such fats in their system also makes them an easier target for predators. This is why most of these creatures fail to form these compounds prior to the onset of cool weather.

A cold snap in mid-summer that produces an unusual frost would kill many forms of life that could endure freezing conditions as the equinox approaches. Any spider, caterpillar, dragonfly, or beetle that is encountered returning to an active state following a bout of frost is probably capable of withstanding temperatures in the upper 20’s, at least during this time in the season. (And it is also probably better eating now than during the summer.)

In an attempt to extend their lives, some organisms that are sensitive to freezing are known to retreat to places in which the temperature remains above 32 degrees when the surrounding air falls below. Slugs, worms, and harvestmen remain in the confines of debris on the forest floor. In heavily wooded settings, the canopy of leaves that still exists overhead can keep the temperatures close to the ground to a non-lethal level.

It is the nocturnal organisms, like moths, spiders, earwigs, crickets and mosquitoes that are most adversely impacted by the outbreak of cold weather, as night dwellers are forced to contend with an intensity of cold that would be at least a month later for those critters that only exit their shelters during the light of day. Also, creatures that are active in open places must be prepared for the cold before those that live in confined places.

A variety of bugs and plants continue to function weeks after being exposed to a frost or freeze. (A freeze is when dew forms at night and then the temperature of the air drops below 32 degrees, allowing these droplets to solidify into ice. A frost is when the temperature plunges below freezing before any dew can form, so that the moisture that eventually condenses from the atmosphere forms as crystals of ice.) It often takes a hard freeze to eliminate most seasonal organisms, and even than a wooly bear caterpillar, or a small brown moth may be seen well after the start of the hunting season.

The season’s first frost is rapidly approaching, although averaged out over a multi-year period, it has been getting progressively later every year. The summit of the peaks are the first to experience this event, followed by the higher elevation slopes and locations where cold air naturally settles. Eventually, the lowland valleys will experience this defining point in the ecological calendar. For people with school age children, Labor Day marks the official end of summer, but for individuals that spend too much time observing nature, the first frost signals that summer has officially come to an end.

Photo Courtesy Ellen Rathbone.

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Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

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