What is my "Basis"?
Since revenue generated from timbersales is taxed under capital gains and not as income your basis in your timber is an important number to know.
When you purchase or inherit property you need to allocate what the land is worth and what the timber is worth. When you sell timber, you will pay capitol gains on only that part beyond it's original worth. If you bought open land and planted trees on it your timber basis would be your establishment cost.
Any improvements that you do to the roads, culverts, gravel, etc. can be added to the land basis and taken when the property is sold.