I have a 20-year old cedar that is turning brown in patches from the
bottom up.

Let's start with the fact that I'm not a gardener and have minimal
knowledge and experience in gardening or tree care.

I'm not even sure this tree is a cedar. I have some good digital
photos I could share. Can the photos be posted within a message here?

In any case, my location is near Sonoma, California. The tree has
always been healthy and good-looking. There has been no recent
digging or activity anywhere near it.

I phoned a tree contractor I've used for trimming in the past, but
like so many contractors around here, he doesn't return my calls.

I'm reluctant to call the national company that serves this area. In
the past, I've had them shrug their shoulders as to a diagnosis, but
recommend a spraying program. I took them up on this twice and lost
the trees involved.

I'm open to all advice, including possibly other newsgroups or
usenets.

I'd hate to lose this tree and hope someone can help steer me in the
right direction.

BC