All of this work has long since been abandoned. It led nowhere. All that was obtained were deformed freaks, absolutely useless in forestry. Maybe occasionally some oddity could be of ornamental value, but never able to live on its own in natural conditions. A glance through literature on mutations outside forestry quickly convinced me that the pattern is similar everywhere.
Mutations are either neutral or detrimental.
Positive ones, if they do occur, are too rare to be noticeable. Stability in nature is the rule. We have no proofs for Evolution from mutation research. It is sometimes claimed that strains of diseases resistant to antibiotics, or weeds resistant to herbicides, are evidence for positive mutations. This is not so.