Ecosystems

, Volume 13, Issue 1, pp 157–170 | Cite as

Additive Partitioning of Diversity Reveals No Scale-dependent Impacts of Large Ungulates on the Structure of Tundra Plant Communities

  • V. T. Ravolainen
  • N. G. Yoccoz
  • K. A. Bråthen
  • R. A. Ims
  • M. Iversen
  • V. T. González
Article

Abstract

Large herbivores can change ecosystem functioning by impacting plant diversity. However, although such impacts are expected to be scale-dependent in ecosystems with wide-roaming ungulates, scaling issues rarely enter empirical assessments. We here test the hypothesis that the impact of increased reindeer abundance on plant diversity in alpine tundra is scale-dependent. Based on potentially high productivity of the focal habitat units and hence the possibility of positive grazer impacts on plant diversity we predicted higher α and β diversity at the habitat scale where reindeer densities are high. We also explored whether there were differences in diversity patterns at larger scales, including the scale of reindeer management districts. We estimated grazing disturbance as high versus low reindeer density in selected districts (a total extent of 7421 km2) of Northern Norway where reindeer-induced vegetation shifts are debated. We focus on dominance patterns because they can quantify the vegetation state and thus performed additive partitioning of Simpson diversity on multiple scales assessing also species’ contributions to diversity. Contrary to our predictions, we found only weak scale-dependent effects of reindeer grazing on plant diversity. Under high reindeer densities there was evidence for a landscape-scale homogenization of the vegetation, but the predicted α and β diversity increases at the habitat scale were not found. Consistently through all scales considered, four shrub species contributed the most to plant diversity. These results contradict the idea that reindeer at high stocking densities induce shifts in plant species dominance in productive habitats. We conclude that context-dependencies such as spatial scales of management units and habitat types need to be explicitly considered in evaluations of the impacts of large ungulates on plant diversity.

Keywords

grazing tundra ecosystem shrub dominance abundant reindeer productivity gradients landscape elements management scale Fennoscandia 

Supplementary material

10021_2009_9308_MOESM1_ESM.doc (24 kb)
Supplementary material 1 (DOC 24 kb)
10021_2009_9308_MOESM2_ESM.doc (48 kb)
Supplementary material 2 (DOC 47 kb)

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • V. T. Ravolainen
    • 1
  • N. G. Yoccoz
    • 1
  • K. A. Bråthen
    • 1
  • R. A. Ims
    • 1
  • M. Iversen
    • 2
  • V. T. González
    • 1
  1. 1.Department of Arctic and Marine BiologyUniversity of TromsøTromsøNorway
  2. 2.Sami CollegeGuovdageaidnuNorway

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