The DBH, height and the wood volume of these three pine species are closely correlated to the stand age which can be expressed using the regressive equations, y = a + b, y=a + bx + cx2, and y = a + bx respectively.

• “三松”胸径、树高和材积随林龄的变化规律分别可用y=a+b1nx、y=a+bx+cx~2和y=a+bx回归方程来描述,相关紧密。