lightmapping on static mesh looks wrong

I’m trying to practice making VR games, and am working on a minecraft lookalike zombie fighting simulator (for simplicity’s sake). I’m having an issue with my tree model where, when the lighting is baked, it looks totally wrong:

Even though I’m using an overlapping uv map for the texture, I have a separate UV map for the lightmap:

Does anyone know what might be going on here?

.blend file for the model: Dropbox - Tree.blend - Simplify your life

GitHub repo, if you need to see anything else: GitHub - Sam54123/MinecraftVRGame at 9221e8af49cdf4a61ff55ecd1b7016d1ef03c37e

And here is the livestream where I created this: Creating a Minecraft VR Game - YouTube