Indirect effects in food webs at the Arctic’s edge

我的研究项目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受到替代食物来源或其他捕食者影响的机制。这种理解将提高预测物种损失或环境变化将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的主要陆地捕食者;它们全年的主要猎物是旅鼠，但它们也在夏季和秋季大量捕食候鸟，冬季在海冰上捕食海豹。它们还通过改变物理环境来影响其他物种;通过将养分集中在洞穴，北极狐提高了土壤养分并增加了植物生产力，这可能会吸引旅鼠和其他食草动物。我正在调查北极狐和它们的猎物在丘吉尔附近的间接相互作用，马尼托巴，在哈德逊湾的西部边缘，那里的北方森林过渡到北极苔原。该地点靠近许多北极物种分布的南部边缘，气候变化的影响可能很大。与气候变暖相关的海冰减少正在威胁北极熊，北极熊为北极狐提供了吃海豹腐肉的机会。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觅食，以确定红狐是否利用海岸边的苔原洞穴来接近海冰，从而适应北极狐的生态位。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赤狐之间的种间竞争，评估重叠的饮食和空间利用，以应对不同的猎物的可用性，并调查的时间表冻土洞穴占用赤狐，以确定他们是否篡夺北极狐或只是使用未占用的洞穴景观。猎物的可用性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，所以我们也将研究这些间接的影响，通过比较猎物种群和病毒在每个狐狸物种的年度变化。为了评估狐狸生态系统工程的影响，我们将研究旅鼠的饮食狐狸洞穴，确定如何狐狸洞穴促进灌木生长的高地苔原，并对比苔原和森林洞穴的工程效果。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，研究狐狸巢穴对其他生物的重要性将揭示狐狸种群分布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.