Saturday, February 9, 2008

Marking spring...

Our spring season is regulated by our calendar, but nature hears a different drummer. Nature's phenological calendar cycles through reproduction and migration, growth and wilt, activity and rest, and life and death. Nature's seasons are not regulated by our calendar, but by the flow of energy through the biosphere.

February skunk cabbage, Ross Lake fen, Ross County

I mark the commencement of spring with the first big bubble of warm moist air carried on south winds from our Gulf of Mexico to my backyard in south-central Ohio. Warm rain comes with the moist air; its warmth soaks energy into cold soil: Life responds.

American Robins follow the rain north. Flocks become more common, particularly in woodlands, after these early warm rains thaw the soil. Troops of hungry robins glean the leaf litter, noisily tossing leaves over looking for squirmy protein: And they flock through scrubby growths and along forest edges gleaning the last of the dried fruits from last year's crop, under the watchful eye of the local wintering mockingbird.

Small numbers of male Red-winged Blackbirds return with the first warm rain. Quickly, they stake their claim on a good marshy territory sure to attract a mate. Not long afterward they begin their display and they sing across the subdued marsh as it slowly wakes to onrushing Spring.

A few first Turkey Vultures wing north on a friendly south wind, sometimes discovering a few hardy brothers lingering in the cold north, more often joining raucous Black Vulture flocks squabbling over space on shared winter roosts.

Throngs of waterfowl move north in increasing numbers, too. Dabblers find open water on melting lakes and ponds to rest, and scatter in the morning to feed over large areas of thawing farm fields. Divers arrive and join a wintering flock to raft and feed in open waters of thawing lakes, sometimes more than two-thirds feeding under water at the same time.

Night life thrives in the first warm rain. Saturated soil raises worms to wet roadways and wakes amphibians into surges of movement toward vernal pools. Life gleams in the headlights of vehicles and a sad toll is taken.

Plants respond in subtle ways. Tree buds expand as surges of sap rise during these first warm sunny mornings. Embryonic leaves and flowers develop in miniature under tightly sealed bud scales, ready to burst out later in the season when warmth lingers longer.

Skunk cabbage, the earliest bloomer, aided by consistent warmth from groundwater springs, and able to generate its own additional warmth through remarkable living chemistry, raises thick fetid 'flowers' above the muck of fens. Skunk cabbage blooms very early, melting its way through snow and thin ice to be ready for the first waves of insect pollinators rising with the coming of warmth. The odor and the purplish mottling of the enveloping spathe and the organ-colored spadix inside may be adaptations to attract specialized pollinators that seek out the smell and appearance of thawing winter-kill carcasses torn open by hungry scavengers.

There are skunks everywhere after the first warmth of the season. They prowl for food, and more so for mates. Skunks find speeding cars and soon roadsides are littered with black and white carcasses; another sad toll.

The cold always returns after this first warmth. Remarkable amphibians, especially the Ambystomidae, our local mole salamanders, spotted, Jefferson's, leave eggs in vernal pools and disappear for another year, or remain under ice until the next warmth. Birds reverse migrate just as far as needed to find food available. Tree sap drops and buds wait for the next warmth to continue their certain expansion. Skunk cabbage flowers endure in freezing muck by generating their own heat, while mammal skunks return to their burrows to enjoy geothermal warmth.

Skunk cabbage begins nature's annual phenological calendar in southern Ohio. Its blooming echoes the first tap of nature's different drummer; the introductory note of a new season's symphony of life. The first warm rain riding a Gulf breeze north raises the orchestra.

No comments: