Our Window on Nature

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Ghostly Remnant Of A Forest

Filed under: Trees — Lowell Christie -- February 13, 2008 @ 3:39 pm

Chestnut TreeSitting on our desktop there’s a weathered twist of wood that we like to think is American chestnut. We found it near the top of a North Carolina peak and carried it, sodden and heavy with the remnants of winter, all the way down to the motorhome. In spite of the fact that one of us was jabbed in the back every step of the way by a wooden elbow, you could legitimately call our botanical artifact a ghost — the ghost of a race of trees that once covered the Blue Ridge Mountains.

A few old folks remember seeing trees like this one, whose uppermost leaves fluttered more than 100 feet in the air. They speak of tree trunks measuring more than four feet around, and of branches so heavy with nuts that you could gather them up by the wagonload. They talk of the lumber turned into houses and fences and railroad ties, and of bark stripped off and sold for tanning hides. They recall when chestnuts roasting over an open fire was more than the words of a song sung around Christmas time.

Walk in the forests of the Blue Ridge Mountains today and you find only a few half-hidden trunks moldering into soil, and a few defiant saplings tilting like Don Quixote against impossible odds.

Around the turn of the century, a fungus from Asia — Endothia parasitica — entered North America, presumably along with saplings of Chinese chestnut trees. The first person to notice the fungus was a state forester working in the Bronx. Back in 1904, he saw apparently healthy trees develop cankers which, once they encircled the tree trunks, girdled them as surely as man could ever do with an ax. Naturally, the trees died.

Remember hearing about how smallpox almost wiped out the American Indians because they lacked natural immunity? Well, something very like this happened to our American chestnut. Over time, Asian chestnut trees had developed sufficient immunity to withstand the fungus, but when the trees transported it to American shores, the alien disease found a totally vulnerable host. So vulnerable, in fact, that vast forests of dead and dying American chestnut trees soon spread from Maine to Alabama.

Acres and acres of bare trees in the midst of summer must have been a depressing sight back then, especially in places where chestnuts once grew in nearly pure stands. Gradually, nature covered over the wounds, first with ground cover, then shrubs, and finally with a mature, but different, forest.

The American chestnut hasn’t completely died out even yet. It’s barely hanging on, because like the coast redwood, chestnuts sprout from the trunk as long as the roots are alive. It seems incredible that after all of these years you can still find a fair number of chestnut saplings, each one apparently determined to be the individual who survives the fungus that killed the others.

As we drove and hiked all along the Blue Ridge one summer, we noticed so many of these doomed but beautiful young trees — doomed because the same fungus that destroyed the original forests still lies in wait in the parent stump and roots. Most saplings reach no more than a few feet tall before they succumb. You can see it coming — leaves yellowing before their time, brown edges, a general look of malaise. And you can’t help feeling depressed knowing that so far there is little hope of outsmarting the fungus.

Still, since some American chestnuts survive, scientists continue to look for either a blight-resistant strain of tree or for some type of biological control. More recently, they have been hoping to find a control fungus — one that renders the original one less lethal to its host.

Up in western Michigan, in locations one can only hope are a carefully kept secret, we’re told there remain pockets of American chestnut trees so far untouched by the disease. Outside the normal range and still producing abundant chestnuts, these descendants of saplings brought to Michigan by early settlers may provide the last source of genetic material should a way to cope with the fungus be found.

Whether they do it by controlling the original disease, by a new fungus controlling the original fungus, or by the development of a resistant strain of tree, if a control is to do any good, it must come soon. But even if a solution should be found tomorrow, there will never be an unbroken forest of American chestnuts stretching before our eyes. Yet, when we remember those dying saplings in the Blue Ridge, it’s good to know that there are scientists hoping to make that sight possible for future generations.

UPDATE: Researchers have now created a hybrid between the American and Chinese (blight resistant) chestnut trees. It is said to have 95% of the genes of the American tree and the resistance of the Asian tree and is being planted on the east coast. Perhaps the chestnut will return.



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