So I will get the best start if I just chop the trunk below the first branch and throw away the rest. No air layering the top part?
This is route 6 I can take with this tree
Alnus, the Adler's, are pretty common. If you want a second alder, just wander along a creek, and the shrubby thickets will be a blend of alders and shrubby dogwoods and maybe a willow or two. Alders are not often seen in nurseries because they are viewed as being too common and too plain, no special saleable feature. Don't get me wrong, your's is nice, just saying as landscape material they don't have a "big wow factor". All through Europe alder of one species or another are pretty common in the mesic zone just above wetlands. Where cattails stop, the alders can start.
If you were to do an air layer, you would delay beginning work on the tree at least on year, possibly two. If you dug the tree up, and did the air layer while it was getting established in a pot, the energy available will be largely gone by the time you do the trunk chop. Back budding will be poor, compared to my proposal. When a tree is dug from the ground, the stored energy is at a maximum. You need this to get low buds to pop. The air layer process will drain that energy away. It would take a number of years for the tree to get back to the level of stored energy it had when first dug up. A weak tree might only pop a bud or two, a strong tree could produce dozens.
Just my thoughts as to what I would do.
