The exterior of a tree isn’t always a good reflection of its internal condition – think of it as “can’t judge a book by its cover” applied to books’ raw material.
In Connecticut, as NPR reports (read/listen to the story here) there’s an interesting research project developing a sort-of-low-tech, sort-of-high-tech way to determine the internal health of trees without damaging them:
To do that, Marra hammered nails into the trunk of a sugar maple in northwest Connecticut, girdling the tree with sensors. Then, he circled and tapped on each nail. Each tap was recorded by a computer. Marra’s recording sound waves. Measuring how fast sound travels from the nail he hits, to all the other nails around the tree.
It’s called “sonic tomography.” Think of it like a CAT scan for trees. A way to peer inside a trunk without drilling to see if a tree is rotting — or solid wood. “The denser the wood, the faster the sound waves,” Marra said.
The spur for his project is calibrating how much carbon trees store, but it seems like it could be applied to other forest-health issues.
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David, Knowing how maples handle incursions like that (actually taps is what I have seen) they heal by forming an internal scar. Maple people know that and avoid tapping above a previous tap incursion, as it will impede the sap flow. If the tree is big enough to not block the lack of communication next year’s test might well work as the tree is communicating across a separate plane from last years test, but wonder if the sound travel alone will effectively give a good health record.