间伐对杉莲混交林中乳源木莲树冠结构的影响

Impacts of Different Intermediate Cutting on Crown Structure of Manglietia yuyuanensis in Mixed Stands with Cunninghamia lanceolata

以福建省沙县15年生(13年生时间伐)和17年生(10年生时间伐)的乳源木莲 杉木中龄混交林(杉莲比为7∶3)为研究对象,通过应用Ruark异速生长模型,对间伐后混交林中乳源木莲的树冠结构进行研究。结果表明,在混交条件下,不同间伐期对树冠形状有显著影响:13年生时间伐,乳源木莲树冠生长受到限制不能充分扩展,树冠形状近似抛物线形,枝长分布方式对下部层次造成遮荫,不利于乳源木莲树木的光合作用;而10年生时间伐,乳源木莲具有圆锥形树冠、较大的枝倾角和较高的叶面积指数,因此有利于树冠对光的截获,从而增加单株生物产量,有利于培育乳源木莲大径材。杉莲混交林中乳源木莲累积叶面积指数可以分别用以下模型进行估测:y(10年生时间伐)=2 6211Z0 1318е0 0417Z(R2=0 9418)和y(13年生时间伐)=1 7546Z0 6122е-0 1411Z(R2=0 9923)。通过残差百分比检验和后验检验表明,模型拟合度较高,预测效果良好。

The stands of 17-year-old and 15-year-old Manglietia yuyuanensis mixed with C.lanceolata (the ratios of C.lanceolata to M.yuyuanensis was 7∶3) at Shaxian County in Fujian Province,which respectively given different intermediate cutting in 10th year and 13th year were studied.The crown structure (including vertical distribution of primary branches, crown form, vertical changes of branch inclinations, vertical distribution of leaf area and cumulative leaf area index) of M. yuyuanensis in mixed stands were studied by asynchronous speed growth model.The results showed that different intermediate cutting patterns had significant effects on the crown structure. With timely intermediate cutting,most trees of M.yuyuanensis were with coniform crowns, otherwise crown form appeared parabolical cylinder crowns. The conical-shaped crown,large branch inclination and higher leaf area index were contributed to the absorption of the sunlight and the silviculture of large-diameter wood of M.yuyuanensis. The cumulative leaf area index of M.yuyuanensis could be estimated by the index models,respectively,A_(CLAI)=2.621 1Z()^(0.131 8)е^(0.041 7Z)(R^2=0.941 8) and B_(CLAI)=1.754 6Z()^(0.612 2)е^(-0.141 1Z)(R^2=(0.992 3)).Validation on the data showed that the model of M.yuyuanensis leaves area could give more accurate estimation.