Tom's Blog

Wednesday, July 27, 2011

Bur oak longevity, but not forever

The bur oak (Quercus macrocarpa) is a long-lived tree throughout most of its range, but does not live forever. In 1997 we lost a 200-year old tree, and just last week we lost another oldie. This tree had lost a large upper branch about a year ago, and now, as the photos show, the whole tree has been uprooted. I am assuming that last year's limb loss destabilized the tree so that the large branches on the downhill side pulled the tree over, perhaps when the roots had been weakened.

I don't have the age of this tree yet but the big bur oak we lost in 1997 had 200 rings. After we get the trunk and branches cleaned up (a late fall task), we can hopefully smooth out the base so that the rings can be counted.

This latest loss was a little sad, because this was one of our most photogenic trees. In fact, Kathie's winter photo shown here won an award about 10 years ago. The tree that came down is the one on the right.

These two trees have always been a landmark at Pleasant Valley Conservancy which we have called "the two bur oaks". Now that there is only one, the landmark is gone.

Last week another large bur oak in the neighborhood went down also. This tree was in the pasture on the Schultz farm, about a mile away (see photo below). According to Jim Schultz, this tree uprooted suddenly last Wednesday evening about 9 PM at a time when there was not even a breath of air. Presumably it had also become destabilized in an early wind event, and finally gave up the ghost.

I was saddened to see the Schultz tree go because it was such a characteristic open-grown pasture tree, sitting all alone on its hillside. I have always assumed that Schultz's hillside was characteristic of what many southern Wisconsin pastured savannas looked like when they were heavily grazed. Even though all the understory was gone, the character of the savanna could be observed by the shapes of the big old bur oaks.


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