不同林龄杉木人工林冠幅与生长因子的关系

Relationship between crown width and growth factors in Chinese fir plantation among different stand ages

【目的】研究杉木人工林不同生长期冠幅因子及林分生长因子对其影响程度,为建立更好的冠幅预测模型及目标树经营提供理论依据,达到优化森林经营管理措施的目的｡【方法】以广西贝江河林场3个不同林龄的杉木纯林为研究对象,布设9个20 m×20 m标准样地并展开全面调查,利用相关分析法及通径分析法探讨林分生长因子(胸径、树高)对冠幅因子(冠幅、冠长率、冠形率)的影响｡【结果】1)各林龄林分胸径和树高均随林龄增大而增加,且平均胸径和树高间差异显著(P<0.05)｡2)各林龄林分冠幅及冠长具有显著差异(P<0.05),冠幅介于1.0~14.0 m之间,冠幅增长主要集中于中龄林和近熟林｡3)冠长率介于0.06~0.89之间,总平均冠长率为0.61,均值在中龄林时达到最大(0.70),成熟林最小(0.46)｡4)树高对冠幅具有显著的正向作用且随着林龄增长逐渐减弱,胸径只在成熟林阶段对冠幅有正向作用｡5)胸径与冠长率之间一直为负相关关系,趋势为先减小后增大,树高对冠长率的影响随林龄增长由正向转为负向｡6)胸径对冠形率的影响作用随林龄增长由正向转为负向,树高对冠形率具有正向作用且随林龄增长呈先增大后减小的趋势｡【结论】由于杉木在不同发育期自身生长权衡机制,冠幅及冠形率在不同的生长阶段主导因子并不相同,因此在不同发育期灵活选取生长指标估测冠幅比通过单一指标估测更为准确.

【Objective】In order to establish better crown prediction model and provide theoretical basis for target tree management,and achieve the ideal structure for forest management,the relationship of crown width factors in Chinese fir plantation among different growth periods and the influence degree of tree height and DBH on crown width were studied.【Method】Taking three growth periods pure Chinese fir forests in Guangxi Beijianghe forest farm as the research object,nine standard plot of 20 m×20 m were laid,the DBH,tree height,crown width,crown height and so on of Chinese fir were investigated completely,the influence of stand growth factors on crown width factors was discussed by the correlation analysis method and the path analysis method.【Result】1)The DBH and tree height increase with the stand age and have significant differences between growth periods(P<0.05).2)The crown width and crown height of three forest ages have significant differences in different stand ages(P<0.05),the crown width mainly increases from the middle age to the near-mature period,and the figure range from 1.0 m to14.0 m.3)The crown length ratio is between 0.06 and 0.89 and the average is 0.61,the maximum average(0.70)appears at middle age and the minimum average(0.46)presents at mature age.4)The tree height has a significant positive effect on crown width,and this positive effect is gradually decreased with the increase of stand age,and the DBH only has a positive effect on crown width at the mature age.5)There is always a negative correlation between DBH and crown length ratio,and the trend is found to first decrease and then increase.The effect of tree height on crown length ratio changes from positive to negative with the increase of stand age.6)With the increment of stand age,the influence of DBH on crown rate changes from positive to negative.Tree height has a positive effect on crown shape rate,which increases firstly and then decreases as stand age increases.【Conclusion】Due to there is different growth trade-off mechanisms in different growth stages in Chinese fir,and the dominant factors of crown width and crown shape rate are different in different growth stages,so it is more accurate to estimate crown width by flexible selection of growth indexes than by single index at different growth stages.