Rupp T Scott, Olson Mark, Adams Layne G, Dale Bruce W, Joly Kyle, Henkelman Jonathan, Collins William B, Starfield Anthony M
Department of Forest Sciences, University of Alaska Fairbanks, 99775, USA.
Ecol Appl. 2006 Oct;16(5):1730-43. doi: 10.1890/1051-0761(2006)016[1730:stiovf]2.0.co;2.
Caribou are an integral component of high-latitude ecosystems and represent a major subsistence food source for many northern people. The availability and quality of winter habitat is critical to sustain these caribou populations. Caribou commonly use older spruce woodlands with adequate terrestrial lichen, a preferred winter forage, in the understory. Changes in climate and fire regime pose a significant threat to the long-term sustainability of this important winter habitat. Computer simulations performed with a spatially explicit vegetation succession model (ALFRESCO) indicate that changes in the frequency and extent of fire in interior Alaska may substantially impact the abundance and quality of winter habitat for caribou. We modeled four different fire scenarios and tracked the frequency, extent, and spatial distribution of the simulated fires and associated changes to vegetation composition and distribution. Our results suggest that shorter fire frequencies (i.e., less time between recurring fires) on the winter range of the Nelchina caribou herd in eastern interior Alaska will result in large decreases of available winter habitat, relative to that currently available, in both the short and long term. A 30% shortening of the fire frequency resulted in a 3.5-fold increase in the area burned annually and an associated 41% decrease in the amount of spruce-lichen forest found on the landscape. More importantly, simulations with more frequent fires produced a relatively immature forest age structure, compared to that which currently exists, with few stands older than 100 years. This age structure is at the lower limits of stand age classes preferred by caribou from the Nelchina herd. Projected changes in fire regime due to climate warming and/or additional prescribed burning could substantially alter the winter habitat of caribou in interior Alaska and lead to changes in winter range use and/or population dynamics.
北美驯鹿是高纬度生态系统的重要组成部分，也是许多北方民族的主要生存食物来源。冬季栖息地的可用性和质量对于维持这些北美驯鹿种群至关重要。北美驯鹿通常会利用下层有充足地衣（一种优质冬季草料）的老龄云杉林地。气候和火灾模式的变化对这一重要冬季栖息地的长期可持续性构成了重大威胁。利用空间明确的植被演替模型（ALFRESCO）进行的计算机模拟表明，阿拉斯加内陆地区火灾频率和范围的变化可能会对北美驯鹿冬季栖息地的丰度和质量产生重大影响。我们模拟了四种不同的火灾情景，并跟踪了模拟火灾的频率、范围和空间分布以及植被组成和分布的相关变化。我们的结果表明，阿拉斯加内陆东部内尔奇纳北美驯鹿群冬季活动范围内火灾频率缩短（即反复发生火灾的间隔时间缩短），将导致短期和长期内可用冬季栖息地相对于目前的情况大幅减少。火灾频率缩短30%导致每年烧毁面积增加3.5倍，景观中云杉-地衣林数量相应减少41%。更重要的是，与目前存在的森林年龄结构相比，火灾更频繁的模拟产生了相对不成熟的森林年龄结构，很少有林分年龄超过100年。这种年龄结构处于内尔奇纳鹿群偏好的林分年龄类别的下限。由于气候变暖或额外的规定火烧导致的火灾模式变化可能会极大地改变阿拉斯加内陆北美驯鹿的冬季栖息地，并导致冬季活动范围使用和/或种群动态的变化。
