Naturalist's Journal: Here's to solar power—the engine of autumn's ... - The Westerly Sun

Naturalist's Journal: Here’s to solar power-the engine of autumn’s color show | Guest Columns | thewesterlysun.com

‘October is the month of painted leaves. Their rich glow now flashes round the world.”

So wrote naturalist and philosopher Henry David Thoreau in an essay called “Autumnal Tints” that was published in the prestigious Atlantic Monthly in October 1862. The article is timeless, and, then as now, being featured in the Atlantic is a sign that the writer has hit the big time and has something important to say. But while eternally vital has long categorized the several million words that HDT produced over his too-short lifetime—he died young, at age 44, on May 6, 1862—”big time” was never anything Thoreau experienced. Sadly, by the time “Autumnal Tints” appeared in print, much to the delight of the magazine’s influential readership, Henry had been dead for close to half-a-year.

Still, I’d like to think that from his resting place in Concord, Massachusetts, on the “Author’s Ridge” of the Sleepy Hollow Cemetery, HDT and his companions, which include Ralph Waldo Emerson, Nathaniel Hawthorne, and Louisa May Alcott, among others, have reveled in the changing of the leafy trees that overhang their graves. No doubt Thoreau, if such things are possible in the afterlife, has continued to celebrate the “rich glow” of the foliage as those painted leaves dominate the autumn landscape.

No doubt Thoreau is also scratching his head in confusion and consternation that the transformation is no longer on a dependable time schedule. In all too many cases, global climate change has thrown carefully documented phenoiogies—phenology is the study of nature’s timing—out the proverbial window. That said, Henry could still find something familiar in the color show now taking place on the ridge and beyond.

Pretty close to arriving at the age-old proper time, we have our yellows. Right on cue, we have our yellow leaves.

We’re graced with our foliage palette of autumnal tints because of a complex interplay that involves a number of factors, some of which are essentially set in stone while others can vary widely and wildly over time.

The dependable part of the show is directed by the sun, or, more specifically, by the numbers of hours of daylength. This, it goes without saying, changes on a daily basis, but it does so on a clockwork schedule, and so plants, as well as animals, have evolved ways to build it into their genes as a clock and calendar that times numerous critical processes.

For the fauna, the key one at this point of the year is migration and other strategies for dealing with the upcoming Big Chill in our region. So critters such as birds have developed a schedule, which is set by predictable and, over millennia, reliable declines in what’s technically known as the photoperiod, to get ready for the Change well enough in advance to avoid having the cold wreaking havoc on their ability to cope.

For example, among our avian friends bent on heading south, this involves, even in the face of beach weather, shrinking their breeding organs and thereby lightening their traveling load. For the birds that will be staying put, this can also involve reconfiguring their digestive systems to process seeds and berries instead of insects, which will soon be unavailable. As long as there’s an abundance of fish and tasty invertebrates to eat, gulls, egrets, and shorebirds will hang around to work the waters, but in due time, the sun will be sending a message: get out of here while the gettin’s good. Avoid this warning at your peril.

If your body is covered in fur rather than feathers, the solar timepiece will tell you that you’ll want to start putting on extra layers of fat and scouring the landscape for a suitable place out of the coming cold. That advice also holds for animals like reptiles and amphibians, which will soon be heading below the frostline for the duration, and for insects, many of which will get through the frostbite season as freeze-resistant eggs, larvae, or even adults, (A few members of the spineless corps, of course, famously migrate to frost-free climes.)

Among plants, the decline in daylength sends a signal that it’s time to stop making the green pigment chlorophyll, the molecule that directs the process known as photosynthesis, by which the plant world turns carbon dioxide and water into plant food and oxygen. As the green disappears, a vanishing act that’s first visible in such species as the Hay-scented Fern and the Poison Ivy, you start seeing something that was, up until that point, completely hidden, at least to us.

Chlorophyll, it turns out, isn’t the only player in the photosynthetic drama. There’s an entire cast of supporting actors, known as accessory pigments, that handle various wavelengths of sunlight and efficiently power photosynthesis. The accessories come in tints of yellow and orange, but their presence is masked by green—until now.

As chlorophyll makes its molecular exit, the so-called carotenoids—think the color of carrots and pumpkins, along with the leaf color of autumn birches and spicebush—take center stage. it is a transformational glow that, noted Thoreau, “flashes round the world.”

The carotenoid show, which is directed by the sun, will always be our lot at about the middle of October. But, long experience has taught us, there could be something more—something magical.

Dependable theater can be, well, a little bland. Over the decades, we New Englanders have learned to crave, even expect, a color show that moves us into another dimension—the Yankee Magazine October Cover dimension. You know the image, the one with the brilliant white church steeple flanked by maples and other hardwoods exhibiting a riot of reds and other colors, including purples. This is quite a bit less dependable than the carotenoid display, and there are a number of years in which the show fails to put in much of an appearance. This makes it all the more thrilling when just the right combination of warm days, cool nights, and dry weather combine over the proper stretch of days to allow the leaves to craft anthocyanins, a group of chemicals that appear to protect the leaf from sun damage as well as provide a warning to insects inclined to harm the foliage that the leaf-bearing plant is ready, willing, and able to defend itself. The unmistakable message to the enemies of the foliage state is, to use the words that President Biden delivered recently to potential foes of Israel, simply this, “Don’t.”

Maybe they’ll listen.

It’s hard to know what kind of warning the trees will post this year. While the temperature regime has been right on target, we’ve had more rain than is good for pigmentation—anthocyanins are water soluble, so too much ill-timed precipitation can actually wash away the finest color show autumn has to offer—and these days, climate change has made it possible to predict when, or if, there’ll be a peak in autumn tint production.

We no longer can know what normal is.

You just have to get outside and discover it.

A Note to Readers: If you’re interested in joining me on a guided tour designed to highlight color change biology and the techniques “journalists”—or, better put, journalers—use to document their colorful observations, please join me on Saturday, October 21st, from 10 to noon, at the Avalonia Land Conservancy’s Tefftweald at Birchenturn preserve in North Stonington. For more information and to sign up, visit https://avalonia.org/event/documenting-discoveries-at-tefftweald-at-bir….