贡嘎山海螺沟林线附近峨眉冷杉种群的结构与动态

Structure and Dynamics of Abies fabri Population Near the Alpine Timberline in Hailuo Clough of Gongga Mountain

通过对贡嘎山海螺沟海拔 35 80m处 1.0hm2 峨眉冷杉 (AbiesfabriCraib)林的定位调查 ,分析了峨眉冷杉的个体生长、种群结构与动态、干扰及更新特征。结果表明 :1)林线附近的环境胁迫影响了个体的形态发育和高、径生长 ,但对其更新繁殖无明显影响 ;2 )静态生命表和种群生存曲线反映了 2 0a以前和 6 0～ 140a分别经历的强烈环境筛选和竞争自疏 ,以及后期与环境变化相关的死亡率波动 ,峨眉冷杉寿命极限为 40 0a左右。 3)林线种群遭受高频率、小规模的林隙干扰。尽管 86 .4%的林隙由多木形成 ,但死亡的峨眉冷杉以枯立为主导致林隙较小 ;病害、冰雪和死树的打压是林隙形成的重要因素 ,而风不是这里林线环境的主要自然干扰。 4)峨眉冷杉的幼苗表现了相当的耐荫性 ,尽管其更新依赖林隙的存在 。

Through a detailed field study on a 1.0 hm 2 plot at 3 580 m a.s.l. in Hailuo clough of Gongga Mountain, the characteristics of individual growth, population structure and dynamics, natural disturbance and gap regeneration of the timberline population of Abies fabri Craib were analyzed. The results suggested that, while apparent stresses on the development of configuration, and growth of height and diameter were shown in A. fabri individuals, the effect on regeneration was undetected. An intensive environmental selection and competitive self-thinning were detected at the age of 0-20 a and 60-140 a respectively through the specific-time life table and the survivorship curves of the timberline population. The fluctuation of death rate in the later stage was also shown to be relative to environmental variation. The life limit of A. fabri is 400 a or so near the upper timberline. The A. fabri population near timberline is disturbed by the gaps in a high frequency and small scale. Although 86.4% of the gaps are induced by more than one gap-maker, most of them are small as the major gap-maker A. fabri died standing. Disease, ice and snow, and hitting by the dead trees are the main causes of gaps, whereas wind is not an important disturbance agent near the timberline. The seedling of A. fabri is fairly shade-tolerant, although the regeneration of the species shows dependence on the existence of gaps. More than one factor on different spatial scales should be responsible for the regeneration pattern of A. fabri.