Redshift

311292_10100642487686448_377148968_nOne of the most striking aspects of autumn is that rich, copper light that slants in low over the horizon to casts long shadows over the landscape and overstate even the subtlest details of geographic relief and texture before dripping like April dew from the fiery leaves.

Photoperiod acts like a cosmic metronome, setting the four-quarter time for the biotic cycles of the natural world. Everything, from fruit maturation, breeding cycles, migration patterns to feeding habits, etc, follows the tempo set by the earth’s trajectory around the sun, and the angle of that angle.

With respect to the sun, the earth is set on an angle just a little over 23 degrees. Without that angle, there would be no seasonality, no photoperiod. During summer, our latitude faces the sun almost directly, during winter our piece of the earth (here in the southeast) is oriented slightly away from the sun by a little over 23 degrees latitude.

earth-seasons
Notice that the angle of the earth is tilted with respect to the sun (indicated by the red arrows). If those arrows were oriented up and down with respect to the sun, seasonality would not exist.

During the summer months, the sun traces out an arch through the sky whose apex is almost directly overhead. However, by early September we begin to notice the sun hanging lower in the sky each day. As the sun’s arching path over North America leans further towards the southern horizon, the light pitches down at a lesser angle, passing through more of the atmosphere before finally striking the earth’s surface. Consequently, the frequency of light that our eyes perceive as the color “red” scatters, that is to say, the light “redshifts”. Come fall, that elegant, redshifted sunlight slants through the fiery canopy and drips off the autumn leaves like April dew.

By late September, warblers begin their migration over the Southeast. The decreasing daylight initiates their journey from their summering grounds in Canada to their wintering grounds in South Florida and beyond. The small, colorful birds eat almost exclusively insects and tend to avoid urban areas; in fact, many species of warbler depend on unbroken tracts of forest along their migration route. September through October is the best time to catch a glimpse of one of these handsome and energetic creatures. A great place to encounter one is along a stream bank or moist bottomland flanked by dense vegetation with an adjacent mature forest canopy – conveniently, also a great place to wait for your buck.

1914665_679990701148_5448662_nThose of us who take to the trees every autumn with high hopes of venison have a front-row seat to the drama of autumn light. Photoperiod largely governs a whitetail’s social and behavioral patterns. Beginning in late August, hormonal changes begin to occur in both bucks and does. The waning daylight causes testosterone levels in bucks to spike, which in turn causes the soft, velvety antlers to harden and the bucks to relieve themselves of the now itchy, peeling velvet. The curled shreds of bark at the base of saplings attest to the bucks’ high-strung aggravation.

Come autumn, there is only one place to find a whitetail: in the hardwoods. Acorns are a staple dietary component of deer and other wildlife. They also testify to the opulence of season, and more than once I have found the urge to try one irresistible. I don’t know when I’ll finally learn not to let my curiosity get the best of me; I hope never. Tannic acid is the plant’s mechanism to make its fruit less palatable to would-be predators; though it does not seem to be especially effective at deterring much more than curious, hardheaded Southern boys. In those tannic, oaken morsels are the crucial complex carbohydrates – long chains of sugar molecules – that are stored as an energy bank to see the animal through winter’s frosty nights and leafless woods.

Acorns from the white oak family, including the white oak (Quercus alba) and the chestnut oak (Quercus dentatum), among a few others, take only one year to mature, while those of the red oak group including northern red img_1463-676x507oaks (Quercus rubrum), southern red oaks (Quercus falcata), water oaks (Quercus nigra), willow oaks (Quercus phellos), and many more, take two years to mature. That may not sound like a pertinent fact, but it is. If a mid-April frost nips the tender young buds of the white oak acorns, the white oak crop may be poor the following autumn. However, the red oak acorns were already over a year old and thus heartier during the same frost. This staggered arrangement of acorn maturation ensures that, come autumn, there will always be acorns in the hardwoods. That nature never places all of her eggs in the same basket stands as a testament to t14324175_10102791102629878_7261893305757590901_ohe supreme craftiness of the biotic mechanism.

Recognizing the subtle goings in nature is the greatest mark of woodsmanship. It keeps our minds working and our wits sharp, and best of all, there is always something new to see and try to understand.

Hunter S. Bridges

    

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