Aldo Leopold Wilderness Research Institute, Rocky Mountain Research Station, USDA Forest Service, 790 E. Beckwith Avenue, Missoula, Montana, 59801, USA.
Northern Forestry Centre, Canadian Forest Service, Natural Resources Canada, 5320 122nd Street, Edmonton, Alberta, T5H 3S5, Canada.
Ecol Appl. 2018 Mar;28(2):573-586. doi: 10.1002/eap.1671. Epub 2018 Feb 20.
In many forested ecosystems, it is increasingly recognized that the probability of burning is substantially reduced within the footprint of previously burned areas. This self-limiting effect of wildland fire is considered a fundamental emergent property of ecosystems and is partly responsible for structuring landscape heterogeneity (i.e., mosaics of different age classes), thereby reducing the likelihood of uncharacteristically large fires in regions with active fire regimes. However, the strength and longevity of this self-limiting phenomenon is not well understood in most fire-prone ecosystems. In this study, we quantify the self-limiting effect in terms of its strength and longevity for five fire-prone study areas in western North America and investigate how each measure varies along a spatial climatic gradient and according to temporal (i.e., annual) climatic variation. Results indicate that the longevity (i.e., number of years) of the self-limiting effect ranges between 15 yr in the warm and dry study area in the southwestern United States to 33 yr in the cold, northern study areas in located in northwestern Montana and the boreal forest of Canada. We also found that spatial climatic variation has a strong influence on wildland fire's self-limiting capacity. Specifically, the self-limiting effect within each study area was stronger and lasted longer in areas with low mean moisture deficit (i.e., wetter and cooler settings) compared to areas with high mean moisture deficit (warmer and drier settings). Last, our findings show that annual climatic variation influences wildland fire's self-limiting effect: drought conditions weakened the strength and longevity of the self-limiting effect in all study areas, albeit at varying magnitudes. Overall, our study provides support for the idea that wildland fire contributes to spatial heterogeneity in fuel ages that subsequently mediate future fire sizes and effects. However, our findings show that the strength and longevity of the self-limiting effect varies considerably according to spatial and temporal climatic variation, providing land and fire managers relevant information for effective planning and management of fire and highlighting that fire itself is an important factor contributing to fire-free intervals.
在许多森林生态系统中，人们越来越认识到，在先前燃烧区域的足迹内，燃烧的可能性大大降低。这种野火的自我限制效应被认为是生态系统的基本突现属性，部分原因是它构造了景观异质性（即不同年龄类别的镶嵌体），从而降低了在活跃火区中出现异常大火灾的可能性。然而，在大多数易发生火灾的生态系统中，这种自我限制现象的强度和持久性还没有得到很好的理解。在这项研究中，我们根据五个易发生火灾的北美的研究区域来量化其自我限制效应的强度和持久性，并研究每种措施如何沿着空间气候梯度变化，以及根据时间（即年度）气候变化而变化。结果表明，自我限制效应的持久性（即自我限制效应的年限）范围从美国西南部温暖干燥的研究区域的 15 年到位于蒙大拿州西北部和加拿大北方森林的寒冷北部研究区域的 33 年。我们还发现，空间气候变化对野火的自我限制能力有很强的影响。具体而言，与高平均水分亏缺（即较温暖和干燥的环境）相比，每个研究区域内的自我限制效应在低平均水分亏缺（即较湿润和凉爽的环境）地区更强且持续时间更长。最后，我们的研究结果表明，年度气候变化会影响野火的自我限制效应：在所有研究区域中，干旱条件都会削弱自我限制效应的强度和持久性，尽管程度不同。总体而言，我们的研究支持了这样一种观点，即野火有助于燃料年龄的空间异质性，进而调节未来火灾的规模和影响。然而，我们的研究结果表明，自我限制效应的强度和持久性会根据空间和时间气候变化而有很大差异，为土地和火灾管理人员提供了有关有效规划和管理火灾的相关信息，并强调了火灾本身是促进无火灾间隔的一个重要因素。
