• Belyea, R.N.
  

Death of a tree is not a clear-cut event, and the exact time at which it, takes place is difficult to establish with available methods. It is easy to distinguish between a living balsam fir tree and an obviously dead one, and it is in these distinguishable differences that a criterion of death may be found. In the living tree the foliage is green , and the cambial layer when stripped away from the sapwood is milky white in color and, during the summer months, quite moist. In the obviously dead tree, whatever foliage is retained is reddish brown in color, the cambial layer is dark brown and, in trees dead, for some time, dry and tight to wood surface.