Mammalian herbivores confer resilience of Arctic shrub‐dominated ecosystems to changing climate

• Published in: Global Change Biology
• Main Authors: Kaarlejärvi, Elina, Hoset, Katrine S., Olofsson, Johan
• Other Authors: European Commission Framework Programme IV, Nordic Research Initiative, Swedish Research Council FORMAS, JC Kempe Memorial Fund, Gunnar och Ruth Björkmans fond för norrländsk botanisk forskning
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Arctic; Climate change; Tundra
• Online Access: http://dx.doi.org/10.1111/gcb.12970; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.12970; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.12970

Abstract Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub‐dominated systems to warming by studying the change of shrub biomass after a cessation of long‐term experimental warming in a forest–tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low‐biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub‐dominated ecosystems to climate warming.