Structure and tree‐fall gap dynamics of old‐growth Nothofagus forests in Tierra del Fuego, Argentina
Structure and tree‐fall gap dynamics of old‐growth Nothofagus forests in Tierra del Fuego, Argentina
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阿根廷火地岛古老黄毛榉林的结构和树木倒落间隙动态
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
T. Veblen
中科院分区：
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作者：
A. Rebertus;T. Veblen
研究了阿根廷火地岛红木（nothofagus）为主的原生林的树木大小和树龄结构、树木砍伐和林隙特征以及林隙的更新。林隙期的更新导致了矮矮木、白杨和冬青的全龄种群，林隙期的更新似乎维持了混交林种间的共存。小叶草通过提前更新填补了许多空缺，一些个体在林下存续50 ~ 150年。多周期的释放和抑制表明白杨可能利用几个间隙事件到达主冠层。同样，在封闭的冠层下，毛蕊草生长良好，对林隙的形成反应迅速，有时会阻碍毛蕊草的再生。相比之下，矮毛蕨的再生主要来自于种子或小的、短暂的幼苗的提前再生。福建森林林隙的周转期估计为300 - 500年，尽管林隙的形成是高度偶发的，可能与区域性广泛的风暴、地震和林分枯死有关。92%的林隙涉及多次树木砍伐，至少53%涉及二次扩张。火地岛的林窗和树落特征与巴塔哥尼亚北部、智利和新西兰的结果相似；林隙中Nothofagus spp.和Drimys winteri的更新依赖于相关植被，并在局地和区域环境梯度上存在差异。
Tree size and age structure, tree-fall and gap char- acteristics, and regeneration in gaps were studied in Nothofagus-dominated old-growth forests in Tierra del Fuego, Argentina. Gap-phase regeneration has resulted in all-aged populations for N. pumilio, N. betuloides, and Drimys winteri, and regeneration in gaps appears to be maintaining coexist- ence between species in mixed stands. N. betuloides fills many gaps via advance regeneration and some individuals persist for > 150 yr in the understory. Multiple periods of release and suppression indicate that N. betuloides may take advantage of several gap events to reach the main canopy. Likewise, Drimys grows well under closed canopy and can rapidly respond to gap formation, sometimes impeding the regeneration of N. betuloides. In contrast, N. pumilio regen- erates in gaps mainly from seed or from advance regenera- tion of small, ephemeral seedlings. Gap turnover times in Fuegian forests were estimated at 300 - 500 yr, although gap formation was highly episodic and possibly associated with regionally extensive windstorms, earthquakes, and stand-level dieback. 92 % of gaps involved multiple tree-falls, and at least 53 % involved secondary expansion. Gap and tree-fall characteristics in Tierra del Fuego were similar to results from northern Patagonia, Chile, and New Zealand; however, we emphasize that regeneration of Nothofagus spp. and Drimys winteri in gaps depends on associated vegetation and varies along both local and regional environmental gradients.