I have made bows from alder, and like the way it tools and splits. If you are making lower weight bows you can get by with the normal dimensions, for a typical white wood hunting bow, as it is usually a fairly light wood. I have seen quite a variety in density and seen some heavy weight bows made from denser wood found at treeline. A two inch diameter stave will be naturally trapped, and seems to work well.
most will say it is not a bow wood, and advise to look elsewhere, and I can agree if you have a plan for an bow with a lot of features and details, but if you just want to cut some easy to dry and and work staves for for the experience and fun, Its OK for bendy handle, flatter bellied designs.