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Oecologia

, Volume 161, Issue 4, pp 747–758 | Cite as

Herbivore impacts to the moss layer determine tundra ecosystem response to grazing and warming

  • Jemma L. GornallEmail author
  • Sarah J. Woodin
  • Ingibjörg S. Jónsdóttir
  • Rene Van der Wal
Ecosystem Ecology - Original Paper

Abstract

Herbivory and climate are key environmental drivers, shaping ecosystems at high latitudes. Here, we focus on how these two drivers act in concert, influencing the high arctic tundra. We aim to investigate mechanisms through which herbivory by geese influences vegetation and soil processes in tundra ecosystems under ambient and warmed conditions. To achieve this, two grazing treatments, clipping plus faecal additions and moss removal, were implemented in conjunction with passive warming. Our key finding was that, in many cases, the tundra ecosystem response was determined by treatment impacts on the moss layer. Moss removal reduced the remaining moss layer depth by 30% and increased peak grass biomass by 27%. These impacts were probably due to observed higher soil temperatures and decomposition rates associated with moss removal. The positive impact of moss removal on grass biomass was even greater with warming, further supporting this conclusion. In contrast, moss removal reduced dwarf shrub biomass possibly resulting from increased exposure to desiccating winds. An intact moss layer buffered the soil to increased air temperature and as a result there was no response of vascular plant productivity to warming over the course of this study. In fact, moss removal impacts on soil temperature were nearly double those of warming, suggesting that the moss layer is a key component in controlling soil conditions. The moss layer also absorbed nutrients from faeces, promoting moss growth. We conclude that both herbivory and warming influence this high arctic ecosystem but that herbivory is the stronger driver of the two. Disturbance to the moss layer resulted in a shift towards a more grass-dominated system with less abundant mosses and shrubs, a trend that was further enhanced by warming. Thus herbivore impacts to the moss layer are key to understanding arctic ecosystem response to grazing and warming.

Keywords

Arctic Climate change Habitat degradation Herbivory Moss layer 

Notes

Acknowledgments

We are grateful to Hera Sengers and Anne-Mette Pedersen for invaluable help with field and laboratory work and to UNIS for the logistic support provided. This work was funded by NERC (NER/S/A/2001/05958). The experiments conducted within this study complied with the current laws of the country in which they were performed.

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Jemma L. Gornall
    • 1
    • 3
    Email author
  • Sarah J. Woodin
    • 1
  • Ingibjörg S. Jónsdóttir
    • 2
    • 3
  • Rene Van der Wal
    • 4
  1. 1.Institute of Biological and Environmental SciencesUniversity of AberdeenAberdeenScotland
  2. 2.Agricultural University of IcelandReyjavikIceland
  3. 3.University Centre on Svalbard (UNIS)LongyearbyenSvalbard
  4. 4.Aberdeen Centre for Environmental Sustainability (ACES)University of AberdeenAberdeenScotland

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