The results show that in the top of crown,the bifurcation ratio increases with the age from 1 a to 12 a,it comes to maximum at 12 a,then keeps at a comparative high level.

• 结果表明 :马尾松树冠上部的分枝率在 1- 12a阶段为逐级上升 ,到 12a时达到最高值 6 2± 1 8974;