Indirect effects in food webs at the Arctic’s edge

对北极边缘食物网的间接影响

• 批准号: RGPIN-2017-05506
• 负责人: Roth, James
• 金额: $ 2.4万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=631850
• 关键词: Indirect; effects; food; webs; Arctic

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.

我的研究项目考察了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。这种理解将增强预测物种丧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，但它们在夏天和秋天也大量捕食候鸟，冬天在海冰上吃海豹。它们还通过改变物理环境影响其他物种；通过将养分集中在洞穴中，北极狐提高了土壤养分和植物生产力，这可能会吸引旅鼠和其他草食动物。我正在调查马尼托巴省丘吉尔附近涉及北极狐狸及其猎物的间接互动，丘吉尔位于哈德逊湾西部边缘，那里的北方森林过渡到北极冻土带。这一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，北极熊为北极狐狸提供了获取海豹腐肉的途径。最近赤狐入侵冻土带是对北极狐狸的另一个潜在威胁，北极狐狸体型较小，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。我们将研究北极狐狸和赤狐的海洋饲养，以确定赤狐是否利用沿海的苔原洞穴获取海冰，从而采用北极狐狸的生态位。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。我们还将通过评估食物和空间使用的重叠来检查北极狐狸和赤狐之间的物种间竞争，以应对不同的猎物可获得性，并调查赤狐占用苔原洞穴的年表，以确定它们是篡夺北极狐狸还是仅仅使用景观上空置的洞穴。猎物可获得性和捕食者病原体的变化可能会影响对其他猎物物种的捕食压力，因此我们也将通过比较猎物种群和每个狐狸物种中的病毒的年度变化来研究这些间接影响。为了评估狐狸生态系统工程的影响，我们将研究旅鼠的食物对狐狸洞穴的影响，确定狐狸洞穴如何促进高原苔原上灌木的生长，并对比工程对冻土带和森林洞穴的影响。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，研究狐狸窝点对其他生物的重要性将揭示其分布南部边缘狐狸种群的变化对北极生物多样性的更广泛影响。