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Reindeer grazing inhibits climate-driven biodiversity in the Fennoscandian tundra
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  • Juan Ignacio Ramirez,
  • Maya Sundqvist ,
  • Elin Lindén,
  • Robert Björk,
  • Bruce Forbes,
  • Otso Suominen,
  • Torbjörn Tyler,
  • Risto Virtanen,
  • Johan Olofsson
Juan Ignacio Ramirez
Umeå University

Corresponding Author:[email protected]

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Maya Sundqvist
Umeå University
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Elin Lindén
Umeå University
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Robert Björk
University of Gothenburg
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Bruce Forbes
University of Lapland
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Otso Suominen
University of Turku
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Torbjörn Tyler
Lund University
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Risto Virtanen
University of Oulu
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Johan Olofsson
Umeå University
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Abstract

Herbivores in the tundra interact with vegetation through several mechanisms, especially defoliation, trampling and nutrient addition through urine and faeces. Through these mechanisms, herbivores drive shifts in plant species composition, richness and diversity. As reindeer effects on vegetation accumulate over time, they might cascade to other trophic levels, but how and when this happens is poorly understood. Since it is methodologically demanding to measure biodiversity across spatial gradients, an alternative approach is to assess it indirectly via biodiversity indices of vascular plants. Values from the Index of Biodiversity Relevance were coupled with vegetation data from a network of 96 fenced and paired grazed plots across Fennoscandia. We analysed the role herbivory has on plant richness and diversity, and on the number of organisms that depend on the vegetation according to the index values. We also explored how herbivores affect the competitive effects of shrubs on other plants since the dominance of a vegetation type links directly to biodiversity. Vegetation richness and diversity did not present any differences between treatments, yet reindeer had an increasing effect on plant diversity when testing the interaction between grazing and herbaceous vegetation. Three out of six biodiversity indexes were higher in fenced plots indicating a higher number of interactions between plants and organisms from other trophic levels. Finally, herb abundance was negatively related to shrubs in both treatments but with a faster decline in the absence of herbivores, suggesting that herbivory increases plant diversity and decreases the diversity of other taxa by reducing shrub abundance. This study highlights the importance of maintaining herbivore populations in the Arctic to prevent the expansion of climate-driven biodiversity into the tundra. The effect of herbivores on ecological communities is not merely a product of plant diversity but can be quantitatively and qualitatively different.
Submitted to Oikos
27 Jan 2024Review(s) Completed, Editorial Evaluation Pending
29 Jan 2024Editorial Decision: Revise Major
27 Feb 2024Assigned to Editor
27 Feb 2024Submission Checks Completed
27 Feb 2024Review(s) Completed, Editorial Evaluation Pending
28 Feb 2024Reviewer(s) Assigned
24 Apr 20242nd Revision Received
29 Apr 2024Review(s) Completed, Editorial Evaluation Pending
31 May 2024Editorial Decision: Accept