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首页> 外文期刊>Journal of Biogeography >Spatial and temporal variation in historic fire regimes in subalpine forests across the Colorado Front Range in Rocky Mountain National Park, Colorado, USA
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Spatial and temporal variation in historic fire regimes in subalpine forests across the Colorado Front Range in Rocky Mountain National Park, Colorado, USA

机译：美国落基山国家公园科罗拉多山前山脉亚高山森林历史火灾的时空变化

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Aim The historical variability of fire regimes must be understood in the context of drivers of the occurrence of fire operating at a range of spatial scales from local site conditions to broad-scale climatic variation. In the present study we examinefire history and variations in the fire regime at multiple spatial and temporal scales for subalpine forests of Engelmann spruce-subalpine fir (Picea engelmannii, Abies lasiocarpa) and lodgepole pine (Pinus contorta) of the southern Rocky Mountains. Location The study area is the subalpine zone of spruce-fir and lodgepole pine forests in the southern sector of Rocky Mountain National Park (ROMO), Colorado, USA, which straddles the continental divide of the northern Colorado Front Range (40o20' N and 105o40' W). Methods We used a combination of dendroecological and Geographic Information System methods to reconstruct fire history, including fire year, severity and extent at the forest patch level, for c. 30,000 ha of subalpine forest. We aggregated firehistory information at appropriate spatial scales to test for drivers of the fire regime at local, meso, and regional scales. Results The fire histories covered c. 30,000 ha of forest and were based on a total of 676 partial cross-sections of fire-scarred trees and 6152 tree-core age samples. The subalpine forest fire regime of ROMO is dominated by infrequent, extensive, stand-replacing fire events, whereas surface fires affected only 1-3% of the forested area. Main conclusions Local-scale influences on fire regimes are reflected by differences in the relative proportions of stands of different ages between the lodgepole pine and spruce-fir forest types. Lodgepole pine stands all originated following fires in the last 400 years; in contrast, large areas of spruce-fir forests consisted of stands not affected by fire in the past 400 years. Meso-scale influences on fire regimes are reflected by fewer but larger fires on the west vs. east side of the continental divide. These differences appear to be explained by less frequent and severe drought on the west side, and by the spread of fires from lower-elevation mixed-conifer montane forests on the east side. Regional-scale climatic variation is the primary driver of infrequent, large fire events, but itseffects are modulated by local- and meso-scale abiotic and biotic factors. The low incidence of fire during the period of fire-suppression policy in the twentieth century is not unique in comparison with the previous 300 years of fire history. There isno evidence that fire suppression has resulted in either the fire regime or current forest conditions being outside their historic ranges of variability during the past 400 years. Furthermore, in the context of fuel treatments to reduce fire hazard, regardless of restoration goals, the association of extremely large and severe fires with infrequent and exceptional drought calls into question the future effectiveness of tree thinning to mitigate fire hazard in the subalpine zone.
机译：目的必须根据从局部场所条件到大规模气候变化等一系列空间尺度上发生火灾的驱动因素来了解火灾状况的历史变异性。在本研究中，我们研究了落基山脉南部的恩格曼云杉-亚高山冷杉（Picea engelmannii，Abies lasiocarpa）和黑松（Pinus contorta）的亚高山森林的火灾历史和火灾状况在多个时空尺度上的变化。位置研究区是美国科罗拉多州洛矶山国家公园（ROMO）南部地区的云杉杉和黑松林亚高山带，横跨北科罗拉多州前缘（40o20'N和105o40 'W）。方法我们结合树状生态学和地理信息系统方法重建了c的火灾历史，包括森林斑块级别的火灾年份，严重程度和范围。 30,000公顷的亚高山森林。我们在适当的空间范围内汇总了火灾历史信息，以测试局部，中观和区域范围内的火灾起因。结果火灾记录覆盖了c。 30,000公顷的森林，以676棵火烧树木的局部横截面和6152棵树芯年龄样本为基础。 ROMO的亚高山森林火灾主要由罕见的，广泛的，可替代林分的火灾事件主导，而地表火灾仅影响森林面积的1-3％。主要结论雷公藤与云杉杉木类型之间不同年龄林分相对比例的差异反映了当地对火势的影响。小枝松树是近四百年来大火的起源。相反，在过去的400年中，大片的云杉杉木林由未受火灾影响的林分组成。大陆分界线西侧和东侧发生的火灾较少但较大，反映了对火灾状况的中尺度影响。造成这种差异的原因可能是西侧的干旱较少且严重，而东侧的低海拔混合针叶树山地森林的大火蔓延。区域性气候变化是罕见的大火事件的主要驱动因素，但其影响受局部和中尺度非生物和生物因素的调节。与过去300年的火灾历史相比，在20世纪的灭火政策时期，发生火灾的几率并不高。没有证据表明在过去的400年中，灭火已导致火灾或当前森林状况超出其历史性的可变性范围。此外，在为减少火灾隐患而进行燃料处理的背景下，无论恢复目标如何，极大型和严重火灾与偶发干旱和异常干旱的关系都使人们担心减薄树木以减轻亚高山地区火灾隐患的未来有效性。

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