Likewise like the style.
My suggestions:
I think you should remove the AA at the very top as with the second layer. It make the outline feel heavier than elsewhere.
Curve of the top section is not so smooth.
Continue the clean two-colour shading on the trunk.
For fixed objects such as trees I prefer to remove the black outlines betweeen the base and the ground. It helps them feel fixed in the ground rather than floating on top of it.