Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, USA.
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, USA.
Ecology. 2017 Oct;98(10):2506-2512. doi: 10.1002/ecy.1968. Epub 2017 Sep 13.
Treelines in Alaska are advancing in elevation and latitude because of climate warming, which is expanding the habitat available for boreal wildlife species, including snowshoe hares (Lepus americanus). Snowshoe hares are already present in tall shrub communities beyond treeline and are the main browser of white spruce (Picea glauca), the dominant tree species at treeline in Alaska. We investigated the processes involved in a "snowshoe hare filter" to white spruce establishment near treeline in Denali National Park, Alaska, USA. We modeled the pattern of spruce establishment from 1970 to 2009 and found that fewer spruce established during periods of high hare abundance. Multiple factors interact to influence browsing of spruce, including the hare cycle, snow depth and the characteristics of surrounding vegetation. Hares are abundant at treeline and may exclude spruce from otherwise optimal establishment sites, particularly floodplain locations with closed shrub canopies. The expansion of white spruce treeline in response to warming climate will be strongly modified by the spatial and temporal dynamics of the snowshoe hare filter.
阿拉斯加的树木线正在向海拔和纬度更高的地方推进，这是由于气候变暖，为北方野生动物物种（包括雪兔）提供了更多的栖息地。雪兔已经存在于树木线之外的高大灌木群落中，是阿拉斯加树木线处的主要白冷杉（Picea glauca）食草动物。我们研究了在美国阿拉斯加德纳利国家公园树木线附近，“雪兔过滤器”在白冷杉建立过程中所涉及的过程。我们对 1970 年至 2009 年的云杉建立模式进行了建模，结果发现，在野兔数量较多的时期，云杉的建立数量较少。多种因素相互作用影响云杉的啃食，包括野兔周期、积雪深度和周围植被的特征。在树木线处，野兔数量丰富，可能会将云杉排斥在其他理想的建立地点之外，尤其是在有封闭灌木树冠的洪泛区。由于气候变暖，白冷杉树木线的扩张将受到雪兔过滤器的时空动态的强烈影响。
