不同初植密度尾叶桉生长量及经济效益分析

INFLUENCE OF SPACING ON THE YIELD AND ECONOMIC BENEFIT OF EUCALYPTUS UROPHYLLA

在雷州半岛的唐家林场设立了尾叶桉５种初植密度：①１ｍ×３ｍ（３３３３株／ｈｍ２）；②１ｍ×４．５ｍ（２２２２株／ｈｍ２）；③２ｍ×３ｍ（１６６７株／ｈｍ２）；④１．５ｍ×４．５ｍ（１４８１株／ｈｍ２）；⑤３ｍ×３ｍ（１１１１株／ｈｍ２）的试验，分别于２年生、３年生和４年生时进行了调查和经济分析。结果表明：⑴尾叶桉初植密度在１１１１～３３３３株／ｈｍ２范围内，林龄４年内，单位面积产量基本上是随着密度的增大而增大，但平均胸径与树高均随着密度的增加而减小。⑵密度３３３３株／ｈｍ２由于株数多，产量最高，利润也最高。⑶从第３年开始，密度１６６７株／ｈｍ２的材积年生长量增幅最大。⑷５种密度的胸径生长的高峰值都出现在前２年；第３年的生长量几乎减少２／３，造林密度越大，减少量越多；至第４年各种密度的年生长量几乎相近。树高生长的高峰值也都出现在前２年，第３年的生长量减少２／３，第４年又减半，至各种密度的树高年生长量几乎相近。除３３３３株／ｈｍ２的材积生长高峰值出现在第２年之外，其它密度的材积峰值都出现在第３年，第４年开始明显减慢。

A spacing experiment of Eucalyptus urophylla including 5 spacing treatments (3 333 trees/ha, 2 222 trees/ha, 1 667 trees/ha, 1 481 trees/ha and 1 111 trees/ha) was established in Tangjia Forest Farm, Leizhou Peninsula. Measurements were carried out at age of 2, 3 and 4 years. The results indicated that in the range of 1 111～3 333 trees/ha, the higher density, there are higher volume/ha and less of mean DBH and mean height at age 4 years. The treatment of 3 333 trees/ha had the highest volume/ha and benefit/ha; the treatment of 1 667 trees/ha had the highest volume increment at age 3 and 4 years. The increment peak of mean DBH was at the age of 2, then the increment was down by 2/3 at the age of 3, the higher density, the more of decrement. The annual DBH increments of 5 spacing treatments were close at age 4 years. The increment peak of mean height was at age of 2 too, and then it was decreased by 2/3 at age of 3 and decreased by 1/2 at age 4 years. The annual height increments of 5 treatments were close at age 4 years. The increment peak of mean volume was at age 3 years for all treatments except 3 333 trees/ha, which the peak was at age of 2 . The increments were sharply decreased after then.