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闽北天然阔叶林乔木层垂直层次明显，一般可分２～３林层；全林树高变动大，其变动系数随主林层平均年龄增大而增大；各林层树高变动系数总体变化趋势是：第Ⅰ层＞第Ⅱ层＞第Ⅲ层（最高层），第Ⅲ林层树高变动系数随主林层平均年龄增大而减小，第Ⅰ及第Ⅱ林层树高变动系数随主林层平均年龄增大而增大；各林层株数组成总体变化趋势是：第Ⅰ层＞第Ⅱ层＞第Ⅲ层，各林层蓄积组成总体变化趋势正相反；第Ⅱ及第Ⅲ林层株数组成占全林的３１～３６％，蓄积组成却占９２～９４％．
The tree layer of natural broad-leaved forest in North Fujian is obviously vertical and can generally be divided into 2 ~ 3 forest layers. The variation of tree height of the whole forest is large, and its variation coefficient increases with the average age of main forest layer. The overall variation of tree height variation coefficient The trend is: the first layer> the second layer> the third layer (the highest layer), and the tree height variation coefficient of the third forest layer decreases with the increase of the average age of the main forest layer. The tree height variation coefficient of the first and the second forest layer With the average age of the main forest layer increasing, the overall trend of each forest layer composition is: the first layer> the second layer> the third layer, the cumulative changes in the composition of each forest layer is the opposite; the second and third The number of forest layers accounts for 31-36% of the total forest, but the accumulation constitutes 92-94%.