By Ted Watt Gazette Contributing Writer
When I was a kid growing up in the suburbs in Connecticut, the air on weekends in October would be thick with the acrid gray smoke of burning leaves. It was just a part of our world. Leaves were a nuisance, something to be gotten rid of so the green “perfect” lawns wouldn’t look littered. I never liked the smell.
As I grew up and began to think more about it, I realized that burning was not a good solution to the problem. But what to do with all those leaves? Since then I have been composting my leaves and loving the rich soil: “black gold” for my gardens. In my small way, I’m imitating the forest, conserving water and restoring nutrients to the soil.
Composting is nature’s recycling system. Our New England forests take the process of reusing nutrients from fallen leaves to another, more complex level. After the glory of October, leaves fade, fall and carpet the deciduous forest floor. Temperatures drop and leaves mostly stay put, mulching the forest. Snows bury them and there they sit; not inert, but not decomposing rapidly to humus. At least not yet.
With the arrival of warmth and rains in spring, insects, bacteria and fungi gear up! Leaves are chewed and rotted, releasing nutrients for plant growth. This temperature-dependent nutrient availability, however, precedes rapid growth of the native trees and shrubs. Woody plants delay putting out their leaves, not willing to risk the late, hard freezes of April and May that destroy leaves. Many nutrients from the decaying leaves are water-soluble; if not taken up by plants, they leach into groundwater and flow into waterways. So unless something intercepts them, these essential ingredients are lost to the system and not available for plant growth as spring progresses.
But mature ecosystems rarely let a valuable resource go unutilized, and this is where our native spring ephemeral wildflowers—bloodroot, spring beauties, wild leek and, in particular, trout lilies (Erythronium americanum, also known as dog-tooth violet and American adder’s-tongue)—step in.
You may be familiar with dense stands of trout lilies in older forests. This species has a very curious annual cycle. Each spring it grows a foot-long, thin, white, spaghetti-like root called a protocorm. This grows horizontally in the soil, ending six inches below the surface where it forms a kind of bulb called a corm. The corm remains dormant during the heat of summer. In September it breaks dormancy and grows to the frost line, preloaded for rapid growth the next early spring. The living plant spends only one month above ground in the course of a year.
The trout lily’s growing cycle is well timed to intercept the nutrients from the fallen leaves in early spring before the trees leaf out. It incorporates these nutrients into leaves, flowers and seeds. As the trees and shrubs expand their leaves, the canopy closes. Shaded out by their taller neighbors, the trout lilies and other spring wildflower species fade and die, decomposing in their turn, releasing the nutrients for the rapidly leafing and growing trees.
Henry W. Art, professor of biology at Williams College, has been studying the role of the early spring woodland flora in sequestering soluble soil nutrients in early spring. I went on a field walk with Professor Art at one of his research sites in Williamstown and learned about this cycle. He and his colleagues have coined the term “vernal nutrient dam” to describe the ecological role that the trout lily and other forest wildflowers occupy in this habitat. The living system has evolved to fill a seasonal niche to the benefit of forest species who make a living in this variable climate we call New England.
The next time you take a walk in the October woods, enjoy our wonderful fall colors as usual. But as you move through the carpet of fallen leaves, I invite you to muse on the nutrients they hold, their availability and sequestration, and the subtle interactions in this miraculous system.
Ted Watt is an environmental educator/naturalist at the Hitchcock Center for the Environment.
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