When growing a sapling, or updating an existing tree, all of the leaves will decay(with a high tickspeed, this is rather entertaining).
This decay drops apples and sapling as a normal tree would, even though the tree itself should not decay, this leads to forests with no leaves and a lot of item entities.
This is surly just a bug with the snapshot, but it needs to be known to be fixed(I didn't find an existing report of this)
(this happens to all the tree types I tested(spruce, oak, birch)).