Alder I never used if Im no mistaken is that is a flowering shrub related to the birch family.  It rarely gets to extensive sizes or heights.  Im a firm believer that a lot of paleo groups used various species including shrubs and bushes.  I think that plants like that have intermingled grain making for great compression but who knows I have made bows from huckleberry bush, Mt. Laurel, and sumac.  Would u know they work.  Take care.
Russ