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how trees die
1 may 2012
A flourishing persimmon tree, lush with burgeoning fruit, died in our garden last summer – though not in any of the ways that Jeff Gillman catalogues in his thoughtful, informative How Trees Die. The persimmon did not fall afoul of pests, diseases, or parasites. It was getting master-gardener care, not too much or too little of anything. Global warming seemed to suit it fine: it was a fan of 105-degree North Texas sunlight.
What our persimmon couldn't handle was a 40-foot-tall blackjack oak falling directly on top of it like a sledgehammer driving a twenty-penny nail. Among reasons why trees die, smashing to smithereens is a rare cause but an unusually effective one. As Gillman points out, though, most tree deaths are less dramatic, and often a result of misplaced good intentions.
The fall of the blackjack oak should probably be ascribed to "natural causes." It was a double-trunked tree, 70 years old and a good two feet around in each of its boles, and had served 50 years ago as the substructure of an improvised homemade gym set. Each spring it would leaf out and look like it had another 70 years in it. But at heart, it wasn't ready for the inevitable spring storms that rake Texas every year. It fell with awesome power (but missed any buildings). Or at least, I assume it fell with awesome power from the effects it left on the persimmon tree. As it happened, nobody was there to hear it, so the eternal question remains as much of a mystery as ever.
Trees don't necessarily have to die. Gillman cites a spruce tree in Sweden that is 9,500 years old. However, trees that reach such an age are a little like the proverbial axe that's had five new handles and three new blades. Somewhere in biomass, the cells of the Swedish tree are genetically identical to those that were growing after the ice age. But the crown of the tree is "only" a few hundred years old; it has died and grown back many times, in a process of self-coppicing, over millennia. As a matter of fact, our persimmon tree is trying to do much the same thing this spring. It has suckered from the base we couldn't even find eleven months ago, and it's now five feet tall – or at least it has a few spindly five-foot shoots. Trees are survivors.
Still, the principle seems to be that trees don't kill trees; people do. We plant them in unwelcoming climate zones. We take appallingly good care of them, not considering that trees in forests get basically no care at all. We plant too many of them too close together, in monocultures that are susceptible to blights.
Gillman writes miniature exemplary biographies of trees that die from one or another of these fates. They are among the weaker elements of his book. I like better the biographies of real, strongly imagined trees that he finds personal connections to. Usually these are "climbing trees," intimately known by small human primates who frolic in their branches. Last weekend I went looking for a site in the New Jersey countryside where I'd lived at the ages of nine and ten. My favorite climbing tree, an apple, seems to have died over the decades, but various saplings that I knew long ago are now towering over the lot where I used to climb. Not much will threaten them – except development, which tends to kill most living things, and to reduce the diversity of those that remain. I hope some of these enclaves of miniature second-growth forest long resist the subdivider's bulldozer.
Gillman, Jeff. How Trees Die: The past, present, and future of our forests. Yardley, PA: Westholme, 2009.