The American Chestnut: Giants Under Threat.
One seen, never forgotten: The American Chestnut in winter
The loss of the queen of the forests
Did a tiny fungus save man taking the blame?
Take the tallest and thickest tree in the world and it’s operating system - it’s brains if you like - the thin columns of cellular structure that makes it work, the phloem, xylem and cambium, could be scraped off and would hardly fill a small bucket. These are the structures that pump water from the roots to the uppermost leaf; that extract nutrients from the soil and add them to the mix; that aid the magic of photosynthesis, the engine of the sun that allows the tree to live and grow. Broadly speaking, the phloem is the outermost layer (and the inner bark) and transports soluble organic materials using Parenchyma cells; the xylem mainly concerns itself with water transport and the vascular cambium helps with secondary growth: the layers are interchangeable as regards their duties. You will remember from biology 101 that photosynthesis uses sunlight to change carbon dioxide into various sugars.
When we see these enormous structures: redwoods that seem to touch the sky; oaks many yards around the bole and chestnuts that can shelter 100 families from the midsummer sun underneath their spreading crowns…or they once could - we seldom realize that 99% of what we see has no function, apart from hoisting the branches and leaves far above the forest floor, away from the tree‘s competitors, up into the brilliant sunshine. The part we can‘t see, the roots, are responsible for keeping the huge growth fed and watered.
What most people don’t realize is just how fragile these giants can be when some implacable pathogen arrives which feeds on one or all of the thin layers of cells protected by the bark.
You don’t need a chainsaw or razor-edged axes to destroy a great tree: fire won’t do it, they soon recover; lightning will destroy trees, but one in 100,000; we have even managed to reign the lumber industry back a tad in order for much to survive.
Yet one tiny fungus, the Cryphoneltria parasitica, (was Endothia previously) accidentally finding its way from Asia in the early part of the last century, completely wiped out the American chestnut in less than 40 years by devouring the Cambium cells. Were talking about billions upon billions of trees in Appalachia alone - more than 20% of the total tree cover in the area! Older folks born before about 1930 and their kin, (the trees were all but gone by 1940), look nostalgically at old photos of picnics held under these wonderful trees, the shade encompassing hundreds of square yards; it was an incalculable loss to all the mountainous eastern states of the USA in particular. These were perhaps the most beautiful trees in the United States, if not the world. They might grow to more than 200 feet in height with a 14 foot diameter a few feet from the ground. The soaring crown commonly began more than 100 feet above the bole. The wood was also beautiful and used to construct most of the barns in the area for 300 years. In fact, it is interesting to speculate how many of these giants would be standing today if man had replaced a fungus as the predator and the lumber industry had been let loose by the inept Forestry Commission in the last part of the 20th century. At least then we would have seen some advantage from this huge loss of perhaps 40 billion tons of useable timber..
If this blight had struck one hundred years later, in a world more enlightened about genetics and introduced immunity, we might have been able to save the American chestnuts. As it is, disease immune trees have been produced and are being planted in the infected areas. Some of the long “dead” trees still have viable root systems which regularly shoot again. The problem is the blight still waits in the woods - fungi are patient adversaries - and the new shoots rarely become mature enough to breed. Cryphoneltria releases billions of spores which are carried by the wind, birds and insects to any healthy trees. Huge examples still stand in isolated areas, more than 10 kilometers from blighted neighboring chestnuts, in uneasy majesty, waiting perhaps for members of the species to return, or the soft and bitter touch of falling pathogenic spores.
We have seen similar tragedy befall the Dutch Elm and the Dogwood trees in the USA by other species of blight. All trees are menaced by acid rain. Man’s inroads are unceasing; big money as ever has its way, despite the protests of ecologists. But there has been nothing, I don’t believe, quite as dramatic in the plant world as the annihilation of the marvelous American Chestnut groves in just a few short decades.