Arctic Wildlife Observatories Linking Vulnerable EcoSystems (ArcticWOLVES)

Extensive monitoring of the abundance, timing and success of reproduction, habitat use and diet of key wildlife species (primarily geese, small mammals, shorebirds, avian predators and mammalian predators like foxes and weasels), as well as annual plant production and arthropod diversity and abundance, was conducted at most sites from 2007 to 2009. Our results provide increasing evidence that predation plays a dominant role in the functioning of Arctic terrestrial ecosystems. At one site, less than 10% of the annual primary production was consumed by herbivores but up to 50% of the herbivore production was consumed by predators. The latter proportion also increased over the past two decades, suggesting a strengthening of top-down effects in this food web. Winter habitat quality appears to be a key factor in the population dynamics of lemmings, the primary prey of most tundra predators. Deep snow provides insulation from the cold air temperature, protection from predators and allows winter reproduction, upon which depend the periodic population irruptions of small mammals. However, deep snow is spatially uncommon in the Arctic, thus the distribution and spatial extent of good quality winter habitat may be limiting population irruptions in some regions or years. Radio-tracking of tundra predators such as snowy owls and arctic foxes revealed that they travel over very large areas and they can extensively use the marine ecosystem during winter, when terrestrial food resources are scarce. Snowy owls in particular display a remarkab le nomadism when searching for suitable nesting sites in spring and an outstanding ability to find locally abundant lemming populations, which may contribute to the regional synchrony of lemming population dynamics. We found evidence that the strength of predation decreases with latitude. Using artificial birds¿ nests, we showed that risk of predation decreases by as much as 66% between 53 and 82 N latitude (a 3,400 km distance). We also found that soil-plant-herbivore interactions are quite sensitive to climate warming. On the one hand, earlier thaw or increasing freeze-thaw cycles will likely result in a loss of soil nutrients in some wetland ecosystems, leading to a decrease in plant production and food resource for herbivores. On the other hand, earlier and warmer springs could have a negative impact on the synchrony between the reproductive phenology of herbivores and plant growth, leading to reduced annual production.

2007年至2009年，研究团队在多数样地针对关键野生生物物种（主要包括鹅类、小型哺乳类、鸻鹬类、鸟类捕食者以及狐、鼬等哺乳类捕食者）的丰度、繁殖时机与繁殖成功率、栖息地利用情况以及食性，同时也针对年际植物生产力、节肢动物多样性与丰度开展了大范围监测。本研究结果提供了愈发充分的证据，表明捕食作用在北极陆地生态系统的功能运转中占据主导地位。在其中一处样地，植食动物仅消耗了不足10%的年初级生产力，但捕食者却吃掉了高达50%的植食动物生产量。该比例在过去二十年中持续上升，表明该食物网中的下行控制效应正在增强。冬季栖息地质量似乎是旅鼠——多数苔原捕食者的主要猎物——种群动态的关键影响因子。厚积雪可为旅鼠隔绝低温、躲避捕食者，并支持其冬季繁殖活动，而这正是小型哺乳类周期性种群爆发的基础。但在北极地区，厚积雪的空间分布并不普遍，因此优质冬季栖息地的分布范围与空间规模，可能会限制部分区域或年份的小型哺乳类种群爆发。对雪鸮、北极狐等苔原捕食者的无线电追踪研究显示，它们的活动范围极广，且在陆地食物资源匮乏的冬季可广泛利用海洋生态系统获取食物。其中雪鸮在春季搜寻适宜筑巢位点时，展现出了显著的漫游习性，同时具备极强的定位局地高密度旅鼠种群的能力，这或许是促成旅鼠种群动态呈现区域同步性的重要原因。本研究发现，捕食作用的强度随纬度升高而降低。借助人工鸟巢实验，我们证实：在北纬53度至82度（跨度约3400公里）的区间内，捕食风险最高可降低66%。此外，我们发现土壤-植物-植食动物间的互作关系对气候变暖极为敏感。一方面，冻土提前解冻或冻融循环频次增加，可能会导致部分湿地生态系统的土壤养分流失，进而降低植物生产力与植食动物的食物资源量。另一方面，春季提前到来且气温升高，可能会破坏植食动物繁殖物候与植物生长之间的同步性，最终导致年生产量下降。