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Topography and post-fire climatic conditions shape spatio-temporal patterns of conifer establishment and growth
Fire Ecology ( IF 3.6 ) Pub Date : 2019-10-04 , DOI: 10.1186/s42408-019-0047-7
Caitlin E. Littlefield

Concern is mounting that larger, stand-replacing forest fires may accelerate compositional shifts or conversions to non-forested states under a warming climate. Post-fire climatic conditions influence system trajectories by facilitating or hindering juvenile recruitment. But without an accurate, long-term understanding of where, when, and how climatic variability and other ecological factors affect regeneration, our ability to predict post-fire trajectories is limited. I quantified multiple, interacting facets of post-fire conifer regeneration—including annual establishment rates and growth—one decade after stand-replacing fire on the eastern slopes of the North Cascades, Washington, USA. Sites were stratified across topographic settings to specifically capture the potential for topography to moderate seasonal and interannual climatic conditions. Recruitment of juvenile conifers occurred every year since fire, with considerable species-specific variability across topographic settings and distance to seed source. Juveniles of all species, except lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson), were rarely observed when live, conspecific seed source was more than 75 m away. Lodgepole pine was the only species for which greater distance to live seed source was not associated with lower densities, a pattern attributable to serotiny. Annual establishment rates were strongly correlated with post-fire conditions: rates were highest when growing seasons were relatively cool and moist. A lagged climate signal was apparent in annual growth rates, but standardized climate–growth relationships did not vary across topographic settings, suggesting that topographic setting did not decouple site conditions from broader climatic trends to a degree that affected growth patterns. These results underscore the importance of favorable post-fire climatic conditions in promoting robust establishment and growth while also highlighting the importance of topography and endogenous, stand-level processes (e.g., seed availability and delivery) in shaping recovery over time. Furthermore, these results suggest that, while the growing concern of post-fire regeneration failure may indeed be warranted under some conditions, failure is not yet the rule in all places and at all times. A more detailed understanding of recovery dynamics through long-term monitoring and by examining multiple, interacting facets of regeneration across scales will improve our predictions of where and when regeneration failure or, conversely, robust recovery may occur under a changing climate.

中文翻译:

地形和大火后气候条件塑造了针叶树建立和生长的时空格局

人们越来越担心,在气候变暖的情况下,更大的,可替代林分的森林大火可能会加速成分转变或转化为非森林状态。火灾后的气候条件通过促进或阻碍少年招募而影响系统的运行轨迹。但是,如果无法准确,长期地了解气候变化和其他生态因素在何处,何时以及如何影响再生,那么我们预测火灾后轨迹的能力就受到限制。在美国华盛顿州北喀斯喀特山脉的东部山坡上进行林分替换火灾后的十年,我量化了火灾后针叶树再生的多个相互影响的方面,包括年建立率和年增长率。站点按地形设置分层,以专门捕获地形以适应季节性和年际气候条件的潜力。自火灾以来,每年都会招募幼年针叶树,在不同的地形环境和与种子源的距离上,物种特定差异很大。当活的同种种子源距离超过75 m时,很少观察到所有物种的幼虫,除了白毛松(Pinus contorta var。latifolia Engelm。ex S. Watson)。小枝松是唯一与活种子来源距离较远且密度较低无关的物种,这种模式可归因于绢毛虫。年建立率与火灾后的状况密切相关:当生长季节相对凉爽和潮湿时,比率最高。在年增长率中明显出现了滞后的气候信号,但是标准化的气候-增长关系在各个地形环境中并没有变化,这表明地形环境并未使现场条件与更广泛的气候趋势脱钩,不会影响到生长模式。这些结果强调了良好的火后气候条件在促进稳固的建立和生长中的重要性,同时也强调了地形和内生的,站立的过程(例如,种子的可获得性和交付)在塑造随着时间的恢复中的重要性。此外,这些结果表明,尽管在某些情况下确实有必要增加对火灾后再生失效的担忧,但并不是所有地方和任何时候都存在失效的规律。通过长期监控并检查多个因素,可以更详细地了解恢复动态,
更新日期:2019-10-04
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