Wildfire is a ubiquitous disturbance agent in subalpine forests in western North America. Lodgepole pine (Pinus contorta var. latifolia), a dominant tree species in these forests, is largely resilient to high-severity fires, but this resilience may be compromised under future scenarios of altered climate and fire activity. We investigated fire occurrence and post-fire vegetation change in a lodgepole pine forest over the past 2500 years to understand ecosystem responses to variability in wildfire and climate. We reconstructed vegetation composition from pollen preserved in a sediment core from Chickaree Lake, Colorado, USA (1.5-ha lake), in Rocky Mountain National Park, and compared vegetation change to an existing fire history record. Pollen samples (n = 52) were analyzed to characterize millennial-scale and short-term (decadal-scale) changes in vegetation associated with multiple high-severity fire events. Pollen assemblages were dominated by Pinus throughout the record, reflecting the persistence of lodgepole pine. Wildfires resulted in significant declines in Pinus pollen percentages, but pollen assemblages returned to pre-fire conditions after 18 fire events, within c.75 years. The primary broad-scale change was an increase in Picea, Artemisia, Rosaceae, and Arceuthobium pollen types, around 1155 calibrated years before present. The timing of this change is coincident with changes in regional pollen records, and a shift toward wetter winter conditions identified from regional paleoclimate records. Our results indicate the overall stability of vegetation in Rocky Mountain lodgepole pine forests during climate changes and repeated high-severity fires. Contemporary deviations from this pattern of resilience could indicate future recovery challenges in these ecosystems.

中文翻译：

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过去 2500 年来落基山黑松林对野火和气候强迫的植被响应

野火是北美西部亚高山森林中无处不在的干扰因素。Lodgepole pine (Pinus contorta var. latifolia) 是这些森林中的主要树种，在很大程度上具有抵御高强度火灾的能力，但在未来气候和火灾活动改变的情况下，这种恢复能力可能会受到影响。我们调查了过去 2500 年来黑松林的火灾发生和火灾后植被变化，以了解生态系统对野火和气候变化的反应。我们从美国科罗拉多州奇卡里湖（1.5 公顷湖泊）落基山国家公园的沉积物芯中保存的花粉重建了植被组成，并将植被变化与现有的火灾历史记录进行了比较。分析花粉样本（n = 52）以表征与多次高强度火灾事件相关的植被的千年尺度和短期（十年尺度）变化。在整个记录中，花粉组合以松为主，反映了黑松的持久性。野火导致松树花粉百分比显着下降，但在 75 年左右的 18 次火灾事件后，花粉组合恢复到火灾前的状态。主要的大规模变化是云杉、蒿属、蔷薇科和 Arceuthobium 花粉类型的增加，大约在 1155 年前校准。这种变化的时间与区域花粉记录的变化以及区域古气候记录确定的冬季更潮湿条件的变化相吻合。我们的研究结果表明，在气候变化和反复发生的高强度火灾期间，落基山黑松林植被的整体稳定性。与这种恢复力模式的当代偏差可能表明这些生态系统未来的恢复挑战。