Emergence of beavers as ecosystem engineers in the New Arctic

据报道，近几十年来，海狸的活动范围从北方森林扩展到北极冻土带，改变了冻土带溪流和周围的永久冻土，从局部到区域的规模。在低纬度地区，海狸筑坝可以将溪流、死水和湖泊出口转化为连通的池塘，这反过来又可以改变河道的航道、溪流的温度、泥沙负荷、能量交换、水生生境多样性和营养循环，以及河岸植被。在北极，海狸的影响可能包括促进永久冻土融化，提高溪流温度，改变溪流的季节性冰，以及复杂的生态系统反应。这项研究将1)记录海狸从森林到冻土带地区的运动，2)了解海狸进行的溪流工程将如何改变北极冻土带的景观和溪流，以及3)预测海狸将如何扩展到冻土带地区并改变河流和邻近的生态系统。研究结果将引起当地社区和资源管理者的兴趣，调查小组将在阿拉斯加费尔班克斯召集一次科学家和利益攸关方研讨会，以综合观察结果，比较温带生态系统研究的结果，并澄清苔原生物群特有的海狸扩张的影响。该项目还包括对博士后科学家的支持。在这个项目中，研究人员将结合一种在卫星图像中检测海狸的新遥感技术，包括无人机成像的实地活动，以及海狸栖息地建模，以了解阿拉斯加海狸的扩张是如何改变北极流和河岸生态系统的。他们将使用半自动工作流程来分析陆地卫星图像、高分辨率卫星图像和历史航空摄影，以确定自1950年以来海狸池塘的形成和消失，并绘制自1950年以来海狸扩散到阿拉斯加北极苔原地区及其影响的地图。为了记录海狸对自然环境的短期和长期影响，研究小组将专注于具有海狸建立的时间序列的野外地点，以及那些没有海狸的地点。景观模型将使用当前海狸栖息地的属性来确定阿拉斯加北极苔原的其他合适栖息地，并将其与温带生态系统中的海狸栖息地进行比较。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In recent decades, beavers have reportedly extended their range from the boreal forest into the arctic tundra, altering tundra streams and surrounding permafrost at local to regional scales. In lower latitudes, beaver damming can convert streams, backwaters, and lake outlets into connected ponds, which in turn can change the course of channels, temperature of streams, sediment loads, energy exchange, aquatic habitat diversity and nutrient cycling, and riparian vegetation. In the Arctic, effects of beavers may include enhanced thawing of permafrost, increased stream temperatures, and changes in seasonal ice in streams, as well as complex ecosystem responses. This study will 1) document movement of beavers from the forest into tundra regions, 2) understand how stream engineering wrought by beavers will change the arctic tundra landscape and streams, and 3) predict how beavers will expand into tundra regions and alter stream and adjacent ecosystems. Results will be of interest to local communities and resource managers, and the team of investigators will convene a scientist and stakeholder workshop in Fairbanks, Alaska to synthesize observations, compare results from studies in temperate ecosystems, and clarify impacts of beaver expansion unique to the tundra biome. The project also includes support for a postdoctoral scientist.In this project, the investigators will combine a novel remote sensing technique that detects beavers in satellite imagery, a field campaign that includes drone imaging, and beaver habitat modeling to understand how beaver expansion in Alaska is altering arctic stream and riparian ecosystems. They will use a semi-automated workflow to analyze Landsat imagery, high resolution satellite imagery, and historic aerial photography to identify the formation and disappearance of beaver ponds and map beaver dispersal into and impacts on arctic tundra regions of Alaska since 1950. To document the short- and long-term effects of beavers on the physical environment, the team will focus on field sites with chronosequences of beaver establishment, as well as those where beavers are absent. Landscape models will use attributes of current beaver habitat to identify other suitable habitat across the Alaskan arctic tundra and compare it to beaver habitat in temperate ecosystems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.