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Henni Ylänne. Photo.

Henni Ylänne

Researcher

Henni Ylänne. Photo.

Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability

Author

  • Henni Ylänne
  • Elina Kaarlejärvi
  • Maria Väisänen
  • Minna Männistö
  • Saija H K Ahonen
  • Johan Olofsson
  • Sari Stark

Summary, in English

The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long-term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long-term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long-term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic.

Department/s

  • MERGE: ModElling the Regional and Global Earth system
  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • Centre for Environmental and Climate Science (CEC)

Publishing year

2020-02

Language

English

Publication/Series

Ecological Monographs

Volume

90

Issue

1

Document type

Journal article

Publisher

Ecological Society of America

Topic

  • Ecology
  • Physical Geography

Keywords

  • Fertilization
  • Soil carbon storage
  • Land use
  • Herbivory
  • Open-top chamber
  • Rangifer tarandus
  • Reindeer
  • SEM-analyses

Status

Published

ISBN/ISSN/Other

  • ISSN: 0012-9615