No wood is naturally immune indefinitely to decay, regardless of exposure conditions. Sapwood of nearly all trees has very little resistance to decay when exposed to suitable conditions, although some heartwood of certain species will resist attack by decay fungi for long periods. Large wooden beams are more resistant to collapse during a fire than uninsulated steel beams of similar strength. A layer of char forms on wooden beams which insulates the inside, greatly slowing strength reduction. Steel beams conduct heat rapidly throughout, losing much strength quickly.
All woods have approximately the same fuel value, in Btu per lb.
Trees grown under similar conditions of temperature, humidity and soil moisture availability, all have the same basic characteristics. That means, a branch produced at 10 feet above the ground will remain at 10 feet throughout the life of a tree. The age of a piece of wood cannot be determined just by looking at it. The number of years that it took to produce the piece can be approximated by counting growth rings showing on the end, but the total age of the tree from which it came and the time since cutting cannot be determined this way. Southern pine lumber produced today is not necessarily inferior to lumber cut 50100 years ago.