We have a large sequoia in our front yard (it's roughly 16 feet in circumference at chest height), though I don't know its overall height. Last fall I noticed some thinning of the foliage on approximately the top five feet of the tree only. This summer, the top 5 feet have begun to brown, and the thinning is increasing. The whole rest of the tree appears to be in good health. Any suggestions would be greatly appreciated.
I'm not sure if lightning makes sense in this particular case since the tree is in a small valley, and has a lot of neighbors up-hill from it that are higher. I suppose electricity is fickle, but would a near 100M volt charge only cause slow browning and thinning?
Hard to know. Lightning is extremely variable in how much damage it causes, from none at all right up to this: http://www.pinetum.org/lightning.htm - probably at least in part because lightning strikes themselves are so variable in energy, but also on how wet the tree is with rain (providing an alternative route for the electricity). Otherwise, has there been any change in the soil around the tree, such as compaction by heavy machinery? That could also account for the symptoms observed.
