The demise of fire and "Mesophication" of forests in the eastern United States
The demise of fire and "Mesophication" of forests in the eastern United States
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DOI：
10.1641/b580207
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发表时间：
2008-02-01
期刊：
影响因子：
10.1
通讯作者：
Abrams, Marc D.
中科院分区：
文献类型：
--
作者：
Nowacki, Gregory J.;Abrams, Marc D.
一系列多样化的适应火的植物群落曾经覆盖了美国东部。欧洲殖民地极大地改变了火灾制度，经常增加火灾发生(例如，在北部硬木林区)或大幅减少火灾发生(例如，在高草草原)。尽管发生了这些变化，但从20世纪20年代左右开始的灭火政策大大减少了整个东部的火灾，带来了深远的生态后果。由火维持的开阔土地转变为封闭的郁闭式森林。作为遮荫的结果，耐荫、火敏感的植物开始取代日生(爱晒)、耐火的植物。一个正反馈循环--我们称之为“中生作用”--随之而来，微环境条件(凉爽、潮湿和阴凉条件；较少的可燃燃料层)对于耐荫的中生植物来说不断改善，而对于不耐荫的、适应火的物种来说则不断恶化。植物群落正在经历快速的组成和结构变化，其中一些没有生态先兆。林分层次的物种丰富度正在下降，而且还将进一步下降，因为大量适应火的植物被有限的耐荫、火敏感物种所取代。随着这一进程的继续，恢复适应火灾的生态系统所需的努力和成本迅速上升。
A diverse array of fire-adapted plant communities once covered the eastern United States. European settlement greatly altered fire regimes, often increasing fire occurrence (e.g., in northern hardwoods) or substantially decreasing it (e.g., in tallgrass prairies). Notwithstanding these changes, fire suppression policies, beginning around the 1920s, greatly reduced fire throughout the East, with profound ecological consequences. Fire-maintained open lands converted to closed-canopy forests. As a result of shading, shade-tolerant, fire-sensitive plants began to replace heliophytic (sun-loving), fire-tolerant plants. A positive feedback cycle-which we term "mesophication"-ensued, whereby microenvironmental conditions (cool, damp, and shaded conditions; less flammable fuel beds) continually improve for shade-tolerant mesophytic species and deteriorate for shade-intolerant, fire-adapted species. Plant communities are undergoing rapid compositional and structural changes, some with no ecological antecedent. Stand-level species richness is declining, and will decline further, as numerous fire-adapted plants are replaced by a limited set Of shade-tolerant, fire-sensitive species. As this process continues, the effort and cost required to restore fire-adapted ecosystems escalate rapidly.