EFFECTS OF AN INTRODUCED PATHOGEN AND FIRE EXCLUSION ON THE DEMOGRAPHY OF SUGAR PINE
EFFECTS OF AN INTRODUCED PATHOGEN AND FIRE EXCLUSION ON THE DEMOGRAPHY OF SUGAR PINE
复制标题
引入的病原体和火排除对糖松种群的影响
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
J. Keeley
中科院分区：
文献类型：
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作者：
P. J. Mantgem;N. Stephenson;M. Keifer;J. Keeley
一种引入的病原体，白松疱锈病（Cronartium ribicola），导致整个北美五针松的数量下降。同时，防火隔离导致许多森林类型的林分密集，这可能会对这些一般不耐荫的松树造成额外的压力。火灾排除也允许燃料累积，目前还不清楚受影响的人口将如何应对火灾的重新引入。虽然白松疱锈病和火灾排除是广泛公认的威胁，但记录这些压力源影响的长期人口统计数据很少。我们目前的人口趋势，从2168个人超过5-15年的受影响的物种，糖松（Pinus lambertiana），在几个燃烧和未燃烧的网站在内华达州的加州。基于尺寸的矩阵模型表明，大多数未燃烧的人口有负增长率（l范围：0.82-1.04）。然而，大多数人口的增长率与更替水平（l5 1.0）没有区别，这意味着，如果人口确实在下降，任何这种下降的进展是缓慢的，需要更长的观察来明确确定人口趋势。我们发现人口增长率之间存在显著差异，主要是由于招募率的变化。与疱锈病和压力有关的死亡（即，资源竞争）是常见的，这表明在确定种群轨迹中，疱锈病和火灾排除都有重要作用。15次指定火灾的数据显示，燃烧的直接影响是许多小树死亡，死亡率在五年内恢复到火灾前的水平。尽管糖松的预后不佳，我们的研究结果表明，我们有时间应用和完善管理策略，以保护这一物种。
An introduced pathogen, white pine blister rust (Cronartium ribicola), has caused declines in five-needled pines throughout North America. Simultaneously, fire ex- clusion has resulted in dense stands in many forest types, which may create additional stress for these generally shade-intolerant pines. Fire exclusion also allows fuels to accu- mulate, and it is unclear how affected populations will respond to the reintroduction of fire. Although white pine blister rust and fire exclusion are widely recognized threats, long- term demographic data that document the effects of these stressors are rare. We present population trends from 2168 individuals over 5-15 years for an affected species, sugar pine ( Pinus lambertiana), at several burned and unburned sites in the Sierra Nevada of California. Size-based matrix models indicate that most unburned populations have negative growth rates (l range: 0.82-1.04). The growth rate of most populations was, however, indistinguishable from replacement levels ( l5 1.0), implying that, if populations are indeed declining, the progression of any such decline is slow, and longer observations are needed to clearly determine population trends. We found significant differences among population growth rates, primarily due to variation in recruitment rates. Deaths associated with blister rust and stress (i.e., resource competition) were common, suggesting significant roles for both blister rust and fire exclusion in determining population trajectories. Data from 15 prescribed fires showed that the immediate effect of burning was the death of many small trees, with the frequency of mortality returning to pre-fire levels within five years. In spite of a poor prognosis for sugar pine, our results suggest that we have time to apply and refine management strategies to protect this species.