I've got some silver birch - well established - that my llamas enjoy. It's a dappled shade and the trees are now well trimmed and I can walk under them easily as everything has been munched up to above head height.
My llamas enjoyed stripping the bark off a few trees, especially willow, which subsequently didn't survive the next winter - the bark on these birch seem not to be so tasty.
Another tree that is left well alone is sycamore, but it's not the best looking tree and the seedlings each year that need mowing is amazing!
Mine will eat any sapplings, so they will need protecting until they can fend for themselves, the trees that is!
I'm sure alpacas/llama habits are similar
