间伐强度对杉木中龄林生长和结构的影响

Effect of thinning intensity on the growth and structure of a middle-aged Chinese fir forest

为了实现大径材培育的目标,通过对不同间伐强度处理后3 a的杉木中龄林生长和结构变化进行调查研究。结果表明:间伐能够促进林分胸径的生长,尤其以强度间伐最为显著;间伐对树高无显著影响,树高受立地指数影响较大;平均单株材积随着间伐强度的增大呈现增加的趋势;蓄积量随间伐强度的增大呈减小的趋势。间伐能显著提高林分的大径阶株数比例且大径阶株数比例随间伐强度增大呈增加的趋势。增大间伐强度能够使林分直径分布较为集中,缩小直径分布离散程度。较大强度的间伐能够提高中、大径材的产量,间伐后3a,小、中径材的出材量均随着间伐强度增大而减小,中大径材(中径材+大径材)的出材量为中度间伐>强度间伐>弱度间伐,大径材产量和增长量均随着间伐强度增大而增加,强度间伐的大径材出材量分别是中、弱度间伐的1.43、20.05倍,较强间伐大径材的出材量显著高于弱度间伐,强度间伐更能促进大径材生长。在进行大径材培育时应选择立地条件较高的林地并使用较大强度的间伐。

Large-diameter timber cultivations of a middle-aged Chinese fir forest underwent thinning intensity treatments,and growth and structure change were monitored for three years.Tree thinning promoted the growth of the diameter at breast height(DBH),especially where thinning was most intense.Tree height was not affected by thinning but was affected by the site index.With increased thinning intensity,the average tree volume increased,stand volume decreased,the diameter distribution of the stand was more centralized,and the distribution of the vertical diameter reduced.Increased thinning intensity resulted in more large-diameter trees and higher medium-and large-diameter wood yield.In the three years after thinning,the yield of small diameter timber and medium diameter timber decreased with the increase of thinning intensity.Medium and large diameter timber(medium diameter timber+large diameter timber)was moderate thinning>intensive thinning>weak thinning.The yield and growth of large diameter timber increased with the increase of thinning intensity.Under intensive thinning,large-sized timber yielded 1.43 and 20.05 times more than moderate and weak thinning,With thinning intensity increasing,small-diameter timber yield decreased but large-diameter timber yield increased,showing that intensive thinning can promote large-diameter timber growth.Therefore,it is necessary to select forest land with a higher site index and use intensive thinning when cultivating large-diameter timber.