I thought this was Pacific Ninebark when I first saw the leaves, but the lower stems are not exfoliating and the leaves are not as finely serrated...?
Your first pic shows a shrub/tree with leaves alternate on the branch...this rules out Acer./maple. Acer has leaves opposite on a branch.
So I have a question about this. I have Pacific Crabapple growing in my front yard. It has spines sticking out in every direction from the main stem, and is constantly sending out new shoots from the base of the tree. Also some of the leaves are oval. This tree has none of those characteristics. Is that because this tree is not yet old enough to develop these features?
Seems it might have something to do with light exposure. When I installed a tree guard/mesh around the lower stem of the tree in my yard it seemed to stop sending out shoots.
