(Table 1) Species richness and diversity of tundra plants in herbivore exclosure and control plots near Barrow, Alaska

To determine the role lemmings play in structuring plant communities and their contribution to the 'greening of the Arctic', we measured plant cover and biomass in 50 + year old lemming exclosures and control plots in the coastal tundra near Barrow, Alaska. The response of plant functional types to herbivore exclusion varied among land cover types. In general, the abundance of lichens and bryophytes increased with the exclusion of lemmings, whereas graminoids decreased, although the magnitude of these responses varied among land cover types. These results suggest that sustained lemming activity promotes a higher biomass of vascular plant functional types than would be expected without their presence and highlights the importance of considering herbivory when interpreting patterns of greening in the Arctic. In light of the rapid environmental change ongoing in the Arctic and the potential regional to global implications of this change, further exploration regarding the long-term influence of arvicoline rodents on ecosystem function (e.g. carbon and energy balance) should be considered a research priority.为明确旅鼠（lemmings）在构建植物群落中的作用及其对北极变绿（greening of the Arctic）的贡献，我们于阿拉斯加州巴罗附近的沿海苔原，对已有50余年历史的旅鼠禁入样地（lemming exclosures）与对照样地（control plots）的植物盖度（plant cover）及生物量（biomass）开展了测定。植物功能型（plant functional types）对植食动物排除的响应随土地覆盖类型（land cover types）的不同存在差异。总体而言，地衣（lichens）与苔藓植物（bryophytes）的丰度随旅鼠禁入而升高，而禾草类植物（graminoids）的丰度则有所下降；不过这类响应的强度仍因土地覆盖类型而异。本研究结果表明，持续的旅鼠活动相较于无旅鼠存在的情景，更能提升维管植物功能型（vascular plant functional types）的生物量，同时也凸显了在解读北极变绿格局时，考虑植食作用（herbivory）的重要性。鉴于北极地区正在发生的快速环境变化，以及该变化可能带来的区域乃至全球尺度的影响，针对田鼠亚科啮齿动物（arvicoline rodents）对生态系统功能（ecosystem function，如碳与能量平衡（carbon and energy balance））的长期影响开展进一步探索，应被列为优先研究方向。