Collaborative Research: Effects of warming induced increases in shrub abundance and changing seasonality on migratory songbirds in Alaskan arctic tundra

由于全球变暖，北美洲北极地区正在“绿化”。在过去的几十年里，许多地点记录的灌木的相对丰度和大小都有所增加。关于这一主题的许多研究都探讨了这种向更多木本物种的转变如何影响元素循环，特别是碳，并对区域和全球大气产生潜在的反馈。迄今为止，北极地区更高的营养级对植被变化的反应尚未得到充分研究。几乎完全被忽视的一个群体是迁徙鸣禽。它们与提供庇护所和食物的灌木有着复杂的关系，而这两者都直接受到天气模式的影响。这项研究将描述苔原植被与栖息地中迁徙鸣禽之间的相互作用，这些栖息地在连续五个生长季节中灌木优势不同，天气事件的时间和严重程度也不同。该团队将1）识别并描述灌木优势与天气之间的相互作用，以确定它们如何影响迁徙鸣禽的食物和住所可用性； 2）研究两种鸣禽种群的繁殖成功率如何响应灌木优势和春季融雪时间的变化； 3）测量灌木优势的变化和春季融雪的时间如何影响整个鸣禽群落的组成和规模。多年方法将允许研究北极季节性的年际变化，特别是融雪的时间，如何影响鸣禽群落。由于灌木优势的增加发生得太慢，生物体无法在拨款期间做出反应，因此研究人员将在阿拉斯加北坡的四个研究地点中的每一个研究地点检查开放苔原地块、中等灌木优势地块和高灌木优势地块的栖息地使用情况。其中包括阿提贡谷（Atigun Valley），这是候鸟向北迁徙时最先到达的苔原站之一，以及更北的图利克湖（Toolik Lake），其中还包括另外两个更北的地点，以增加采样的空间规模。在五个项目年内，他们将在所有四个实地地点进行集中采样，以调查植物资源、节肢动物丰度、鸣禽群落组成以及两种鸣禽物种的到达、定居和繁殖成功的时空变化。在五年内，他们希望捕捉一系列天气的年际变化、春季融雪的开始和生物反应，以提供和理解当前的关系，并预测未来气候和植被的变化可能如何影响这些生物。他们还打算验证远程技术的使用情况，通过生物声学记录监测鸟类群落属性，以进行自动化鸟类群落普查。

As a consequence of global warming, arctic North America has been ?greening? over the past several decades, with increases in relative abundance and size of shrubs documented in numerous locations. Much of the research on this topic examines how this shift toward more woody species affects element cycling, particularly carbon, with potential feedbacks to the atmosphere regionally and globally. To date, the response of higher trophic levels to such shifts in vegetation in the Arctic has not been well studied. One group that has been almost completely ignored is migratory songbirds; they have a complex relationship with shrubs that provide both shelter and food, both of which are directly affected by weather patterns. This research will characterize the interactions between tundra vegetation and migratory songbirds in habitats that differ in shrub dominance for five consecutive growing seasons that will differ in timing and severity of weather events. The team will 1) identify and characterize interactions between shrub dominance and weather to determine how these affect food and shelter availability for migratory songbirds; 2) examine how reproductive success of populations of two songbird species responds to variation in both shrub dominance and timing of spring snowmelt, and; 3) measure how both variation in shrub dominance and timing of spring snowmelt affect composition and size of the entire songbird community. The multi-year approach will allow for examination of how interannual variability in arctic seasonality, particularly the timing of snowmelt, impacts songbird communities. Because the increasing shrub dominance is occurring too slowly for organisms to respond to during the time period of a grant, the researchers will examine habitat usage in open tundra plots, moderate shrub dominance plots, and high shrub dominance plots, at each of four study sites on the North Slope of Alaska. These include Atigun Valley, one of the first tundra stops made by migratory songbirds as they travel north, and at Toolik Lake, farther north, including two additional sites farther north to increase the spatial scale of sampling. In five project years, they will sample intensively at all four field sites to investigate spatial and temporal variation in plant resources, arthropod abundance, songbird community composition, and the arrival, settlement and reproductive success of two songbird species. During five years they hope to capture a range of interannual variability in weather, onset of spring snowmelt, and biotic responses to provide and understanding of current relationships and to predict how future changes in climate and vegetation may affect these organisms. They also intend to verify the use of remote techniques for monitoring bird community attributes via bioacoustic recordings for conducting automated bird community censuses.