Well, that sucks. It is technically illegal, and a mature tree is worth thousands of dollars -- something you might want to point out to them -- but punishing people for doing that is hard. However, you would be well advised to mark the property line more clearly, perhaps with a fence. That strongly discourages people from trespassing to destroy your property.

The property line is very clearly marked by a fence. The fence belongs to the neighbors, and they took the chain link down for the arborists, but it's very evident that that one tree is not remotely on the property line. I'm wondering if the arborists made a mistake. The neighbors had marked the trees to come down by tying white plastic tape around them, and there wasn't any on our tree.

Watch the mulberry. There is a high chance it will resprout from the stump; they usually do. So do maples and some other trees commonly used for coppicing. If you have marked the property line clearly, you can probably dissuade your asshole neighbor from continuing to abuse your trees.

Oh, yes, it hadn't occurred to me, but several beloved mulberries in the neighborhood have been cut down while we have lived here -- they were all hollow inside, so I absolve the cutters-down -- and many of them have indeed sprouted thickly and become dense mulberry bushes that even set fruit after a while. I will keep an eye on ours!

As for the sun vs native tree guild issue, it's quite a long property line and I could probably have some of both. I will do some research.

Thank you again for the advice.

P.