On September 8, 2011, Dr. Wieslaw Binienda, an expert on high-energy impacts on materials and structures testifying before the Polish Parliamentary Committee, proved beyond a reasonable doubt that the collision with the birch could not have ripped the outer portion of the wing from the aircraft. While applying all parameters presented in the IAC Final Report in a rigorous finite element analysis, he demonstrated through a virtual experiment that the high-energy impact causes the wing to act like an ax, cutting the birch with only a small amount of damage to the edge of the wing but without any damage to the lifting area of the wing
Interesting!
Correct me if I'm wrong, but didn't the winglet of a Legacy bizjet take the outer half off the left wing of a GOL B737-800 in Brazil in 2006? I wouldn't imagine that the winglet would be as strong as a 30-40cm diameter birch tree.
There is the speed difference to take account of, but it would appear possible for the tree to at least partially sever a wing, even at the lower approach speed. I'm sure there are other accidents that would tend to support this.