The relationship between fire history and an exotic fungal disease in a deciduous forest
The relationship between fire history and an exotic fungal disease in a deciduous forest
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落叶林火灾历史与外来真菌病之间的关系
作者：
E. Holzmueller;S. Jose;M. A. Jenkins
外来疾病从根本上改变了森林生态系统的结构和功能。事实证明，在大片森林中控制外来疾病是困难的，但火灾可能会降低对环境条件敏感的疾病的水平。我们研究了烧焦和未烧焦的栎山核桃林分中的山茱萸种群，以确定在炭疽病感染之前进行燃烧是否减少了由Discula destructiva引起的一种外来真菌疾病-山茱萸炭疽病的影响。我们假设火已经改变了林分结构，并创造了不太利于山茱萸炭疽病的开阔条件。我们比较了四个抽样类别的佛罗里达毛虫密度、健康状况、物种组成和密度：未燃烧的林分，以及在20年内(20世纪60年代末至80年代末)燃烧一次、两次和三次的林分。二次焚烧林分枝密度最大(770株/ha−1)，其次是三次焚烧林(233株/ha−1)、一次焚烧林(225株/ha−1)和未燃烧林(70株/ha−1)。在焚烧林分中，我们观察到佛罗里达小树(胸径5厘米)的冠枯病比未焚烧林更少(P<0.05)。指示物种分析表明，焚烧有利于历史上与栎类-山核桃森林有关的物种，排除了经过近一个世纪的灭火后与次生演替有关的物种。我们的结果表明，火灾可能通过改变森林结构和组成来减缓受到外来病原体攻击的佛罗里达毛虫种群的下降。此外，我们的结果表明，我们采样的烧伤对森林社区具有整体恢复作用，并处于历史火灾制度的火灾回归间隔内。因此，规定的火可以提供一种管理工具，以减少在历史上的焚烧制度下发展起来的真菌病对森林生态系统的影响。
Exotic diseases have fundamentally altered the structure and function of forest ecosystems. Controlling exotic diseases across large expanses of forest has proven difficult, but fire may reduce the levels of diseases that are sensitive to environmental conditions. We examined Cornus florida populations in burned and unburned Quercus–Carya stands to determine if burning prior to anthracnose infection has reduced the impacts of an exotic fungal disease, dogwood anthracnose, caused by Discula destructiva. We hypothesized that fire has altered stand structure and created open conditions less conducive to dogwood anthracnose. We compared C. florida density, C. florida health, and species composition and density among four sampling categories: unburned stands, and stands that had burned once, twice, and 3 times over a 20-year period (late 1960s to late 1980s). Double burn stands contained the greatest density of C. florida stems (770 stems ha−1) followed by triple burn stands (233 stems ha−1), single burn stands (225 stems ha−1) and unburned stands (70 stems ha−1; P < 0.01). We observed less crown dieback in small C. florida trees (<5 cm diameter at breast height) in burned stands than in unburned stands (P < 0.05). Indicator species analysis showed that burning favored species historically associated with Quercus–Carya forests and excluded species associated with secondary succession following nearly a century of fire suppression. Our results suggest that fire may mitigate the decline of C. florida populations under attack by an exotic pathogen by altering forest structure and composition. Further, our results suggest that the burns we sampled have had an overall restorative effect on forest communities and were within the fire return interval of the historic fire regime. Consequently, prescribed fire may offer a management tool to reduce the impacts of fungal disease in forest ecosystems that developed under historic burning regimes.