If there's one area where Minecraft is missing out the most in terms of realism it must be the gravitional physics. Removing the lowest block of a tree in Minecraft leaves the crown and some of the tree's stem left floating in the air.
Not only does this affect the realism of the game but it also radically increases the amount of time you've got to spend cutting down trees.
TreeLogger PE is an amazing mod which let you realistically cut down trees as you do in real life.
Any of the blocks above the wood block you destroyed will automatically fall down on the ground and be able for you to collect. The leaves are also destroyed and the drop rate of getting saplings and apples is similar to without the mod.