川西亚高山林线不同坡向岷江冷杉生长特征研究

A Study on the Growth Characteristics of Abies fargesii var.faxoniana on Different Slope Aspects in the Timberline Ecotones in the Subalpine Area of Western Sichuan,China

【目的】探索坡向对川西亚高山林线交错带岷江冷杉(Abies fargesii var.faxoniana)生长的影响。【方法】在川西亚高山林线交错带设置的阴坡3000 m^(2)(30 m×100 m)和半阴坡4200 m^(2)(30 m×140 m)样地内进行种群调查,采用独立样本t检验,比较了阴坡和半阴坡岷江冷杉的形态大小(树高、胸径和冠幅)差异;用卡方检验,比较了阴坡和半阴坡岷江冷杉幼树和大树(胸径≥15 cm)在种群内的占比。基于林线交错带不同坡向样点的年轮树芯数据,采用单因素方差分析,对阴坡和半阴坡岷江冷杉大树的径向生长速率差异进行了多重比较。【结果】1)半阴坡样地内的岷江冷杉大树的胸径和树高均显著大于阴坡样地(P<0.05)。2)阴坡样地内的岷江冷杉大树在种群内的占比显著高于半阴坡样地(P<0.05),而半阴坡样地内的幼树在种群内的占比显著大于阴坡样地(P<0.05)。3)阴坡或半阴坡的不同采样点间的岷江冷杉大树径向生长速率均无显著差异(P>0.05);而半阴坡样地的岷江冷杉径向生长速率显著大于阴坡样地(P<0.05),前者是后者的1.68倍。【结论】坡向对川西亚高山林线岷江冷杉的生长特征有明显的影响,半阴坡岷江冷杉大树的胸径、树高、幼树密度以及径向生长速率都高于阴坡。

【Objective】This study was aimed to explore the effects of slope aspect on the growth of Minjiang fir(Abies fargesii var.faxoniana)in timberline ecotone of the subalpine area of western Sichuan,China.【Method】Field investigation was conducted in a plot with an area of 3000 m^(2)(30 m×100 m)on the shady slope and a plot with an area of 4200 m^(2)(30 m×140 m)on the semi-shady slope in the timberline ecotone of western Sichuan.The differences in morphological size(tree height,DBH and crown size)of Minjiang fir between shady and semi-shady slopes were analyzed by t-test.The differences in the percentage of seedlings and large trees(DBH≥15 cm)in the population of Minjiang fir between shady and semi-shady slopes were analyzed by Chi-square test.Based on tree-ring core data collected at different sites,the differences in the radial growth rates of Minjiang fir between the slope aspects were analyzed by One-way ANOVA.【Result】1)DBH and height of the large trees on the semi-shady slope were significantly higher than those on the shady slope(P<0.05).2)The percentage of large trees in the population on the shady slope was significantly higher than that on the semi-shady slope(P<0.05),while the percentage of seedlings on the semi-shady slope was significantly higher than that on the shady slope(P<0.05).3)There was no significant difference in the radial growth rates of Minjiang fir among the different sites on the same shady or semi-shady slope(P>0.05).However,the radial growth rate of large trees of Minjiang fir on the semi-shady slope was significantly higher than that on the shady slope(P<0.05),and the former was 1.68 times that of the latter.【Conclusion】The slope aspects showed a significant effect on the growth of Minjiang fir in the subalpine timberline of western Sichuan,China.The DBH,tree height,seedlings density,and radial growth rate of Minjiang fir on the semi-shady slope were all significantly higher than those on the shady slope.