Trophic dynamic of terrestrial Arctic ecosystems under anthropogenic pressure

确定决定食物网动态的机制是生态学的一个关键研究领域；它也是朝着更好地了解生态系统的功能和脆弱性迈出的重要一步。然而，如果不考虑当代人类引起的两大扰动，即气候变化和人类活动，就无法理解这些机制。地球上没有其他地方的全球变暖影响比北极更具威胁性，但在这个基本上未受影响的生物群中，发展和人类的存在正在蓬勃发展。为了充分理解食物网的动态如何受到人类诱导的扰动的影响，还必须考虑到大多数生态系统具有与其他生态系统进行能量交换的能力，例如人类活动产生的食物投入。在评估全球变化对冻土带生态系统的影响程度时，明确了解能量交换在食物网络动态中的作用是先决条件。冻土带生态系统的关键食草动物(如旅鼠)同时减少，而外来捕食者(如赤狐)的存在可能支持其来自人为食物来源的能量需求。冻土带生态系统的这种持续变化引发了关于北极捕食者和北极筑巢鸟类的命运的重大问题，以及受到全球干扰的北极食物网的整体功能。在预测全球环境变化对生态系统的直接和间接影响时，最大的不确定性之一与了解它将如何影响物种相互作用(这里是捕食者-猎物相互作用)有关。我的研究计划的长期目标是调查捕食者和猎物之间的相互作用在北极陆地食物网动态中的作用，以更好地了解它们的功能和对人为干扰的敏感性，例如气候变化和人类诱导的食物补贴。拟议的计划将在两个研究系统(雪雁-北极狐狸相互作用和北极捕食者-补贴相互作用)中进行，并针对两个短期目标：1)调查捕食者-猎物相互作用在调节气候对北极筑巢鸟类和北极捕食者影响中的作用；2)研究气候和人类存在对北极顶端捕食者种群动态和资源利用变化速度和方向的影响。为了实现这些目标，我打算利用关于北极陆地脊椎动物(特别是鹅和北极顶级捕食者)的现有大规模数据集，并在加拿大北极制订新的实地数据获取战略，目的是开展长期研究，以监测北极关键物种的生存和繁殖成功，并实验性地操纵陆地冻土带的一个关键驱动力，即捕食风险。我的方法将包括捕获-标记-重新捕获、稳定同位素、时间序列和路径分析，以及与因纽特社区当地专家的定期咨询。该项目既是综合性的，也是创新性的。首先，这项工作将人类直接和间接扰动下的营养相互作用整合在一个框架内，加强了我们对候鸟及其捕食者种群动态的理解。其次，该方法使用了最先进的分析和监测工具，对北极社区传统生活的核心野生动物物种进行分析和监测。在对几名HQP和北方人进行北极科学培训的同时，从这项研究计划中获得的科学知识将为北极健全的政策和野生动物管理计划提供坚实的基础。

The identification of mechanisms that determine the dynamics of food webs is a key research area in ecology; it also represents a major step towards an improved understanding of the functioning and the vulnerability of ecosystems. However, those mechanisms cannot be understood without considering two major contemporary human-induced perturbations, namely climate change and human activities. Nowhere else on earth are the effects of global warming more threatening than in the Arctic, yet development and human presence is booming in this largely untouched biome. To fully understand how dynamics of food webs are affected by human-induced perturbations, it is also essential to consider that most ecosystems possess the capacity for energy exchanges with other ecosystems, e.g. food inputs resulting from human activities. A clear understanding of the roles of energy exchanges in food web dynamics is a prerequisite when assessing the extent of effects of global changes on tundra ecosystems experiencing a simultaneous decline of their key herbivores (e.g. lemmings) along with an increasing presence of alien predators (e.g. red foxes) that have the potential to support their energy needs from anthropogenic food sources. Such an ongoing transformation of tundra ecosystems raises major questions with respect to the fate of arctic predators and arctic-nesting birds, and to the overall functioning of arctic food webs subject to global disturbances. One of the greatest uncertainties in forecasting the direct and indirect effects of global environmental change on ecosystems is related to understanding how it will affect species interactions (here predator-prey interactions). The long-term objective of my research program is to investigate the role of predator-prey interactions in the dynamics of terrestrial Arctic food webs to better understand their functioning and sensitivity to anthropogenic perturbations, such as climate change and human-induced food subsidies. The proposed program will be conducted in two study systems (snow goose-arctic fox interaction and arctic predators-subsidies interactions) and addresses two short-term objectives: 1) to investigate the role of predator-prey interactions in mediating climatic impacts on arctic-nesting birds and arctic predators; and 2) to study the influence of climate and human presence on the rate and direction of changes in population dynamics and resource use of arctic top-predators. To achieve these objectives, I intend to use existing large-scale datasets on Arctic terrestrial vertebrates (geese and arctic top-predators, in particular) and to develop new field-based data acquisition strategies in the Canadian Arctic aiming at generating long-term research to monitor the survival and breeding success in key arctic species and to experimentally manipulate a key driving force in the terrestrial tundra, i.e. predation risk. My approaches will encompass capture-mark-recapture, stable isotopes, time series and path analyses, together with the regular consultation of local experts in Inuit communities. The program is both integrative and innovative. First, the work integrates trophic interactions under direct and indirect human perturbation in a single framework, strengthening our understanding of the population dynamics of migratory birds and their predators. Second, the approach uses state-of-the-art analytical and monitoring tools on wildlife species at the heart of Arctic communities' traditional life. While training several HQP and northerners in Arctic science, the scientific knowledge gained from this research program will provide a solid base for sound policy and wildlife management programs in the Arctic.