林窗大小对杉木林内南方红豆杉生长与形质的影响

为明确林窗大小对南方红豆杉生长、形质的影响以及珍贵用材培育成效,测定福建省明溪杉木林中25个林窗样地的南方红豆杉的生长、干形和分枝等指标,分析林窗大小与生长、干形和分枝情况之间的关系,将25个林窗样地按不同面积划分为25～50 m² (Ⅰ)、50～75 m² (Ⅱ)、75～100 m² (Ⅲ)、100～125 m² (Ⅳ)、125～150 m² (Ⅴ)5种林窗类型,运用层次分析法构建了珍贵用材评价指标体系,采用多目标决策法评价5种林窗类型的综合效果.结果表明: 林窗大小显著影响南方红豆杉树高、胸径、冠幅、杈干率、通直度、圆满度、尖削度、径高比、枝下高、枝间距、最大侧枝直径等11个生长和形质指标以及综合评价值. 林窗Ⅰ、Ⅱ类型显著促进南方红豆杉的树高、胸径、冠幅的生长.在干形指标方面,林窗Ⅰ、Ⅱ类型显著抑制分杈率和尖削度,提高通直度;林窗Ⅱ类型显著提高圆满度和径高比.林窗Ⅰ、Ⅱ类型显著提高枝下高,降低最大侧枝直径;林窗Ⅰ类型显著提高枝间距. 林窗Ⅰ、Ⅱ类型显著提高珍贵用材综合评价值.在杉木林内南方红豆杉的培育过程中,控制采伐强度、创建面积25～75 m²的林窗可提高培育效果.

Effects of forest gap size on the growth and form quality of Taxus wallichina var. mairei in Cunninghamia lanceolata forests

In order to clarify the effects of forest gap size on the growth and stem form quality of Taxus wallichina var. mairei and effectiveness of the precious timbers cultivation, 25 sample plots in Cunninghamia lanceolata forest gaps were established in Mingxi County, Fujian Province, China to determine the indices of the growth, stem form and branching indices of T. wallichina var. mairei seedlings. The relationships between the gap size and growth, stem form and branching were investigated. The 25 sample plots were located at five microhabitats which were classified based on gap size as follows: ClassⅠ, Ⅱ, Ⅲ, Ⅳ and Ⅴ, which had a gap size of 25-50 m², 50-75 m², 75-100 m², 100-125 m² and 125-150 m², respectively. The evaluation index system of precious timbers was built by using hierarchical analysis. The 5 classes of forest gaps were evaluated comprehensively by using the multiobjective decision making method. The results showed that gap size significantly affected 11 indices, i.e., height, DBH, crown width, forking rate, stem straightness, stem fullness, taperingness, diameter height ratio, height under living branch, interval between branches, and max-branch base diameter. ClassⅠand Ⅱ both significantly promoted the growth of height, DBH and crown width, and both significantly inhibited forking rate and taperingness, and improved stem straightness. ClassⅡ significantly improved stem fullness and diameter height ratio. ClassⅠand Ⅱ significantly improved height under living branch and reduced max-branch base diameter. Class Ⅰ significantly increased interval between branches. ClassⅠandⅡ significantly improved the comprehensive evaluation score of precious timbers. This study suggested that controlled cutting intensity could be used to create forest gaps of 25-75 m², which improved the precious timber cultivating process of T. wallichina var. mairei in C. lanceolata forests.