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，北极的北美一直在变绿？在过去的几十年里，随着灌木相对丰度和大小的增加，许多地方都有记录。关于这一主题的许多研究都考察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，以及对区域和全球大气的潜在反馈。到目前为止，更高的营养水平对北极植被这种变化的反应还没有得到很好的研究。一个几乎完全被忽视的群体是候鸟；它们与既提供住所又提供食物的灌木有着复杂的关系，而灌木和灌木都直接受到天气模式的影响。这项研究将描述苔原植被和候鸟之间的相互作用，这些栖息地在连续五个生长季的灌木优势程度不同，天气事件的时间和严重程度也将不同。该小组将1)确定灌木优势和天气之间的相互作用，以确定这些因素如何影响候鸟的食物和庇护所的可获得性；2)研究两个鸣鸟种群的繁殖成功如何对灌木优势和春季融雪时间的变化做出反应；3)测量灌木优势和春季融雪时间的变化如何影响整个鸣鸟群落的组成和大小。多年方法将允许检查北极季节的年际变化，特别是积雪融化的时间，如何影响鸣鸟群落。由于不断增加的灌木优势发生得太慢，生物在拨款期间无法做出反应，研究人员将在阿拉斯加北坡的四个研究地点中的每一个考察开阔的苔原地块、中等灌木优势地块和高度灌木优势地块的栖息地使用情况。其中包括阿提贡山谷，这是候鸟向北迁徙时首批停留在苔原上的地点之一，以及更靠北的Toolik湖，包括更靠北的两个额外地点，以扩大采样的空间规模。在五个项目年中，他们将在所有四个野外地点进行密集采样，以调查植物资源、节肢动物丰富度、鸣禽群落组成的时空变化，以及两个鸣鸟物种的到达、定居和繁殖成功。在五年的时间里，他们希望捕捉天气的年际变化、春季融雪的开始以及生物反应，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体。他们还打算验证远程技术的使用，通过进行自动鸟类群落普查的生物声学记录来监测鸟类群落属性。

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.