Indirect effects in food webs at the Arctic's edge

我的研究项目是研究食物网中的间接相互作用，以了解捕食者和猎物之间的相互作用是如何受到其他食物来源或其他捕食者的影响的。这种认识将提高预测物种丧失或环境变化如何影响生态系统结构和动态的能力。北极狐是整个北极地区主要的陆地捕食者；它们全年的主要猎物是旅鼠，但它们在夏天和秋天也以候鸟为食，在冬天以海冰上的海豹为食。它们还通过改变自然环境影响其他物种；北极狐通过将养分集中在洞穴中，增加土壤养分，提高植物生产力，这可能会吸引旅鼠和其他食草动物。我正在曼尼托巴省哈德逊湾西部边缘的丘吉尔附近调查北极狐和它们的猎物之间的间接相互作用，那里的北方森林正在向北极苔原过渡。这个地点靠近许多北极物种分布的南部边缘，在那里气候变化的影响可能很大。与气候变暖相关的海冰减少正威胁着北极熊，它们为北极狐提供海豹腐肉。最近红狐入侵苔原是对北极狐的另一个潜在威胁，北极狐体型较小，可能会改变它们的巢穴使用和觅食模式。我将在下一个资助周期培训13名学生，同时解决几个短期目标。我们将研究北极狐和红狐的海洋捕食，以确定红狐是否利用沿海苔原洞穴获取海冰，从而采用北极狐的生态位。利用长期的收获记录，我们将评估狐狸种群对海冰、雪和其他气候变量变化的反应。我们还将研究北极狐和红狐之间的种间竞争，通过评估食物和空间使用的重叠来响应不同的猎物可用性，并调查红狐占用冻土带洞穴的年表，以确定它们是篡夺北极狐还是仅仅使用景观上未被占用的洞穴。猎物数量和捕食者病原体的变化可能会影响其他猎物物种的捕食压力，因此我们还将通过比较每种狐狸的猎物数量和病毒的年度变化来研究这些间接影响。为了评估狐类生态系统工程的影响，我们将研究旅鼠饮食对狐穴的影响，确定狐穴对高原冻土带灌木生长的促进作用，并对比狐穴对冻土带和森林冻土带的工程效应。了解狐狸猎物种群之间的间接相互作用将有助于预测气候变化的更广泛后果，并且检查狐狸巢穴对其他生物的重要性将揭示狐狸种群在其分布的南部边缘的变化对北极生物多样性的更广泛影响。***********

My research program examines indirect interactions in food webs to understand the mechanisms by which interactions between predators and their prey are affected by alternative food sources or other predators. This understanding will enhance the ability to predict how species loss or environmental change will affect ecosystem structure and dynamics. Arctic foxes are the main terrestrial predator throughout the Arctic; their primary year-round prey are lemmings, but they also feed extensively on migratory birds in summer and fall and consume seals on the sea ice in winter. They also impact other species by modifying the physical environment; through concentrating nutrients on dens, Arctic foxes enhance soil nutrients and increase plant productivity, which may attract lemmings and other herbivores. I am investigating indirect interactions involving Arctic foxes and their prey near Churchill, Manitoba, on the west edge of Hudson Bay, where boreal forest transitions to Arctic tundra. This site is near the southern edge of many Arctic species' distributions, where the impact of climate change is likely to be large. Declines in sea ice associated with climate warming are threatening polar bears, which provide Arctic foxes with access to seal carrion. The recent incursion of red foxes onto the tundra is another potential threat to Arctic foxes, which are smaller and may alter their den use and foraging patterns. I will train 13 students in the next grant cycle while addressing several short-term objectives. We will examine marine-based feeding by Arctic foxes and red foxes to determine if red foxes use tundra dens by the coast to access sea ice, thereby adopting the ecological niche of Arctic foxes. Using long-term harvest records we will assess fox population responses to changes in sea ice, snow, and other climate variables. We will also examine interspecific competition between Arctic foxes and red foxes by assessing overlap in diet and space use in response to varying prey availability, and investigate the chronology of tundra den occupancy by red foxes to determine if they usurp Arctic foxes or merely use unoccupied dens on the landscape. Changes in prey availability and predator pathogens may affect predation pressure on other prey species, so we will also examine these indirect effects by comparing annual variation in prey populations and viruses in each fox species. To assess impacts of ecosystem engineering by foxes we will examine lemming diets on fox dens, determine how fox dens promote shrub growth on upland tundra, and contrast the engineering effects on tundra and forest dens. Understanding indirect interactions among fox prey populations will help predict the wider consequences of climate change, and examining the importance of fox den sites for other organisms will reveal the broader impact of changes in fox populations at the southern edge of their distribution on Arctic biodiversity.***********