Forest age distribution under mixed-severity fire regimes : a simulation-based analysis for middle boreal Fennoscandia
Forest age distribution under mixed-severity fire regimes : a simulation-based analysis for middle boreal Fennoscandia
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混合严重程度火情下的森林年龄分布：中北带 Fennoscandia 的模拟分析
DOI：
10.14214/sf.559
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发表时间：
2002
期刊：
影响因子：
1.8
通讯作者：
J. Pennanen
中科院分区：
文献类型：
--
作者：
J. Pennanen
利用模拟模型研究了不同林火条件下未管理森林景观的年龄结构。林龄定义为林分中最老的同龄组的年龄，当大多数火灾不是林分更新时，理论上的平衡林龄分布是钟形或双峰型，以老龄级为主。古老的森林（最古老的队列> 150年）占主导地位的景观，除非火灾是频繁和严重的。模拟结果和分析计算表明，如果一个政权的频繁火灾（约每50年）保持景观占主导地位的古老的森林，那么古老的增长优势持续存在时，火灾的数量减少，尽管相关的火灾严重程度增加。模拟结果被施加到樟子松占主导地位的景观中北部芬诺斯坎迪亚，根据经验的结果是占主导地位的古老的森林火灾频繁时，在19世纪。由于火灾状况的变化可以合理地解释为人为点火次数的变化，因此在火灾不太频繁的早期，原始森林显然也占据了景观。模拟模型是用来产生合理的年龄分布中北部芬诺斯堪的纳维亚森林景观在不同的历史火灾制度。总之，大规模干扰的频率单独预测森林景观动态差，和火灾的严重程度和剩余的林分所发挥的作用需要仔细考虑。维护和恢复旧的生长结构是恢复芬诺斯堪的纳维亚森林景观的自然变异性的关键。
A simulation model was used to study the age structure of unmanaged forest landscapes under different fi re regimes. Stand age was defi ned as the age of the oldest tree cohort in a stand. When most fi res are not stand-replacing, the theoretical equilibrium stand age distribution is either bell-shaped or bimodal and dominated by old age-classes. Old-growth forests (oldest cohort > 150 y) dominate the landscape unless fi res are both frequent and severe. Simulation results and analytical calculations show that if a regime of frequent fi res (about every 50 y) maintains landscapes dominated by old-growth forests, then old-growth dominance persists when the number of fi res is decreased, despite the associated increase in fi re severity. Simulation results were applied to Pinus sylvestrisdominated landscapes of middle boreal Fennoscandia, which according to empirical results were dominated by old-growth forests when fi res were frequent during the 19th century. Since the changes in the fi re regime can be plausibly explained by changes in the number of human-caused ignitions, old-growth forests have evidently also dominated the landscapes earlier when fi res were less frequent. The simulation model is used to produce plausible age distributions of middle boreal Fennoscandian forest landscapes under different historical fi re regimes. In summary, the frequency of large-scale disturbance alone predicts forest landscape dynamics poorly, and the roles played by fi re severity and residual stands need to be considered carefully. Maintaining and restoring oldgrowth structures is essential to regaining the natural variability of Fennoscandian forest landscapes.