Reindeer grazing and tundra soil carbon storage under changing climate

Porolaidunnus ja tundramaan hiilivarastot muuttuvassa ilmastossa

Contact person:Dr Sari Stark
Research group: Global change

Start of the project : 1st May 2012
End of the project : 31st July 2014


At present, tundra ecosystems store large quantities of soil carbon that has been accumulating to the soil over centuries and millennia. It is currently predicted that increasing temperatures by global change will enhance decomposition of these large soil carbon stocks. As a result, tundra soils may start contributing to the increase in atmospheric carbon dioxide. In this project, we experimentally simulate effects of global change with specifically designed warming chambers (ITEX standard open top chambers) in a sub-oceanic tundra ecosystem. Similar treatments are conducted in two cases, tundra that is either ungrazed or grazed by reindeer (Rangifer tarandus). In ungrazed tundra, vegetation is dominated by slow-growing dwarf shrubs (e.g. Betula nana, Empetrum hermaphroditum, Vaccinium vitis-idaea, Vaccinium uliginosum), and in grazed tundra, by different sedges and grasses. We investigate changes in vegetation, soil microbial activity and community composition, ecosystem carbon balance and phenolic secondary metabolites of evergreen and deciduous dwarf shrubs.

This project lasted for five years (2009-2014) and was funded by the Academy of Finland.

Participants and collaboration

  • Dr Sari Stark, Arctic Centre, University of Lapland
  • MSc Maria Väisänen (graduate student), Arctic Centre, University of Lapland
  • Ms. Henni Ylänne (undergraduate student), Department of Biology, University of Oulu
  • Dr. Minna Männistö and Dr. Francoise Martz, Finnish Forest Research Institute, Rovaniemi Research Unit
  • Prof. Johan Olofsson and MSc Elina Kaarlejärvi, Department of Environmental Sciences, University of Umeå, Sweden
  • Dr. Sofie Sjögersten-Turner, Dr. Trevor Drage and Dr. David Large, University of Nottingham, UK


  • Stark, S., Männistö, M., Ganzert, L., Tiirola, M., Häggblom, M. (2015) Grazing influences temperature adaptation of soil microbial community in tundra soil. Soil Biology & Biochemistry, in press.
  • Barthelemy, H., Stark, S., Olofsson, J. (2015). Increased plant productivity by long-term faeces addition in tundra ecosystems. Ecosystems, in press.
  • Stark, S., Männistö, M.K., Eskelinen, A. (2015). When do grazers accelerate or decelerate soil carbon and nitrogen cycling in tundra? – A test of theory on grazing effects at contrasting levels of habitat fertility. Oikos, in press. DOI: 10.1111/oik.01355
  • Stark, S., Männistö, M.K. Eskelinen A. (2014). Soil nutrient availability and pH together constrain microbial extracellular enzyme activities in nutrient-poor tundra. Plant and Soil 383:373–385. DOI: 10.1007/s11104-014-2181-y
  • Stark, S. and Väisänen, M. (2014). Insensitivity of soil microbial activity to temporal variation in soil N in subarctic tundra - Evidence from responses to large migratory grazers. Ecosystems 17: 906–917. DOI: 10.1007/s10021-014-9768-2
  • Väisänen, M., Ylänne, H., Kaarlejärvi, E., Sjögersten, S., Olofsson. J., Crout, N., Stark, S. (2014). Consequences of warming on tundra carbon balance determined by reindeer grazing history. Nature Climate Change 4: 384-388.
  • Francini, G., Liiri, M., Männistö, M.K., Stark, S., Kytöviita, M.-M. (2014). Responses to reindeer grazing removal depends on soil characteristics in low Arctic meadows. Applied Soil Ecology 76:14-25. doi:10.1016/j.apsoil.2013.12.003
  • Väisänen, M., Martz, F., Kaarlejärvi, E., Julkunen-Tiitto, R., Stark, S. (2013). Phenolic responses of mountain crowberry (Empetrum nigrum ssp. hermaphroditum) to global climate change are compound specific and depend on grazing by reindeer (Rangifer tarandus ). Journal of Chemical Ecology 39:1390-1399. DOI: 10.1007/s10886-013-0367-z

 PhD and MSc theses

  • Maria Väisänen: Ecosystem-level consequences of climate warming in tundra under differing grazing pressures by reindeer (PhD thesis, University of Oulu, Department of Biology, December 2014)
  • Henni Ylänne: Porolaidunnuksen vaikutukset hiilitaseeseen tundraekosysteemeissä (MSc Thesis, in Finnish, University of Oulu, Department of Biology, 2012)
  • Alex Nyakumba: 13C solid state NMR analysis of soil organic matter quality (MSc Thesis, Physics’ Department, University of Oulu, 2014)

Analyzing net ecosystem carbon exchange in the field. Photo: Sari Stark.

Experimental plot with warming treatment by open top chamber. Photo: Sari Stark.