White spruce demography and herbivory by snowshoe hares measured along elevational gradients in Denali National Park I - Site Data

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. Because multiple factors interact to influence browsing of spruce, including the hare cycle, snow depth and the characteristics of surrounding vegetation, we collected an array of site variables relevant to spruce-hare interactions in Denali National Park, Alaska. Site variables collected included elevation, landscape position, vegetative cover, and the density of white spruce seedlings, saplings and trees.

受气候变暖影响，阿拉斯加的林线（treeline）正沿海拔与纬度梯度向上推进，为包括美洲兔（snowshoe hare，Lepus americanus）在内的寒温带野生动物类群拓展了适宜栖息的生境。美洲兔现已在林线以外的高灌丛群落中定殖，同时也是阿拉斯加林线优势树种白云杉（white spruce，Picea glauca）的主要啃食者。本研究针对迪纳利国家公园林线附近的‘美洲兔筛选效应（snowshoe hare filter）’展开调查，以解析其在白云杉定植过程中发挥的作用机制。由于包括兔种群周期、积雪深度以及周边植被特征在内的多种因素会共同影响白云杉的取食压力，本研究在阿拉斯加迪纳利国家公园采集了一系列与云杉-美洲兔互作相关的样地变量。所采集的样地变量涵盖海拔、景观位置、植被覆盖度，以及白云杉幼苗、幼树与成树的种群密度。