The fluctuating world of a tundra predator guild: bottom-up constraints overrule top-down species interactions in winter

Global warming is predicted to change ecosystem functioning and structure in Arctic ecosystems by strengthening top-down species interactions, i.e. predation pressure on small herbivores and interference between predators. Yet, previous research is biased towards the summer season. Due to greater abiotic constraints, Arctic ecosystem characteristics might be more pronounced in winter. Here we test the hypothesis that top-down species interactions prevail over bottom-up effects in Scandinavian mountain tundra (Northern Sweden) where effects of climate warming have been observed and top-down interactions are expected to strengthen. But we test this a-priori hypothesis in winter and throughout the 3-4 year rodent cycle, which imposes additional pulsed resource constraints. We used snowtracking data recorded in 12 winters (2004-2015) to analyse the spatial patterns of a tundra predator guild (arctic fox Vulpes lagopus, red fox Vulpes vulpes, wolverine Gulo gulo) and small prey (ptarmigan, L...据预测，全球变暖将通过增强自上而下的物种相互作用（即对小型植食动物的捕食压力与捕食者间的种间干扰），改变北极生态系统的功能与结构。然而，过往研究多偏向夏季时段。由于非生物限制因素更强，北极生态系统的特征在冬季可能更为显著。本研究针对如下假说展开验证：在瑞典北部的斯堪的纳维亚山地苔原（当地已观测到气候变暖效应且自上而下的物种相互作用预计会增强），自上而下的物种相互作用强度将超过自下而上的调控效应。但本研究在冬季以及持续3-4年的啮齿动物种群周期内验证该先验假说，该周期会带来额外的脉冲式资源限制。本研究利用2004-2015年间12个冬季采集的雪地追踪数据，分析苔原捕食者类群（北极狐*Vulpes lagopus*、赤狐*Vulpes vulpes*、狼獾*Gulo gulo*）与小型猎物（雷鸟属*L*...）的空间分布格局。