A piece of pine wood floats on the surface of a lake because the water exerts

Thats odd my answer didnt get published stranged, anhow what I was saying is that due to the surface area and mass of the tree is has enough bouyency to stay afloat because of the surface tension on the water with the tree.

surface tension causes the wood to remain on the surface of the water, and is a result of the cohesion of water molecules being stronger than the force of the wood on the surface