Sari Stark

PhD (plant ecology) / FT (kasviekologia)
Academy research fellow / Akatemiatutkija 2009-2014
Visiting Researcher / vieraileva tutkija 2015
Finnish Cultural Foundation, Lapland Fund / Suomen kulttuurirahasto, Lapin aluerahasto

Tel. +358-40-4844254 (2720)
E-mail: sari.stark at
Global Change research group

Focus of research: I investigate soil carbon and nitrogen cycling in tundra ecosystems and boreal and subarctic forests with special emphasis on soil decomposer microorganisms that are responsible for litter and soil organic matter decomposition. Recently the focus has been in studying effects of global change on northern ecosystems at different levels of grazing intensity, and how plant and soil responses interact to form ecosystem carbon balance that links back to global climate.

Tutkimus: Tutkin maaperän hiilen ja typen kiertoa tunturiekosysteemeissä keskittyen erityisesti kasvien muodostamaa kariketta ja maaperän orgaanista ainesta hajottavien lahottajamikrobien aktiivisuutta sääteleviin tekijöihin. Tutkin muun muassa ilmastonmuutoksen vaikutuksia pohjoisiin ekosysteemeihin ja sitä, miten kasvien ja maaperän vuorovaikutussuhteet vaikuttavat ekosysteemin hiilitaseeseen.

Keywords: Global change, tundra ecosystems, soil ecology, plant ecology, microbial respiration, carbon balance, Empetrum, reindeer, plant phenolics

Globaalimuutos, tundraekosysteemit, maaperäekologia, kasviekologia, mikrobihengitys, hiilitase, variksenmarja, poro, kasvien puolustusaineet


Publications in Arctic Centre

  • Väisänen, M., Sjögersten, S., Large, D., Drage, T., Stark, S. (2015) Long-term reindeer grazing limits warming-induced increase in C release: potential role of soil C quality. Environmental Research Letters 10 094020.
  • Stark, S., Väisänen, M., Ylänne, H., Julkunen-Tiitto, R., Martz, F. (2015) Decreased phenolic defence in dwarf birch (Betula nana) after warming in subarctic tundra. Polar Biology, in press. 
  • Ylänne, H., Stark, S., Tolvanen, A. (2015) Vegetation shift from deciduous to evergreen dwarf shrubs in response to selective herbivory offsets carbon losses: evidence from 19 years of warming and simulated herbivory in the sub-arctic tundra. Global Change Biology, 21:3696-3711. DOI: 10.1111/gcb.12964
  • Stark, S., Ylänne, H. (2015) Grazing in Arctic peatlands – an unknown agent in the global carbon budget. Environmental Research Letters 10 (2015) 051002. DOI:10.1088/1748-9326/10/5/051002
  • Barthelemy, H., Stark, S., Olofsson, J. (2015). Increased plant productivity by long-term faeces addition in tundra ecosystems. Ecosystems, in press. DOI 10.1007/s10021-015-9856-y
  • 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 84: 147-157. DOI:10.1016/j.soilbio.2015.02.023
  • 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, 124: 593–602, 2015. 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. DOI:10.1038/NCLIMATE2147
  • 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


Earlier publications

  • Stark, S., Eskelinen, A. & Männistö, M.K. 2012. Regulation of microbial community composition and activity by soil nutrient availability, soil pH, and herbivory in the tundra. Ecosystems 15: 18-33.
  • Hilli, S., Stark, S., Willför, S., Smeds, A., Reunanen, M. & Hautajärvi, R. 2012. What is the composition of AIR? Pyrolysis-GC-MS characterization of acid-insoluble residue from fresh litter and organic horizons under boreal forests in southern Finland. Geoderma 179-180: 63-72.
  • Stark, S., Hilli, S., Willför, S., Smeds, A.I., Reunanen, M., Penttinen, M. & Hautajärvi, R. 2012. Composition of lipophilic compounds and carbohydrates in the accumulated plant litter and soil organic matter in boreal forests. European Journal of Soil Science 63: 65-74.
  • Kumpula, J., Stark, S. & Holand, O. 2011. Seasonal grazing effects by semi-domesticated reindeer on subarctic mountain birch forests. Polar Biology 34: 441-453.
  • Manninen, O.H., Stark, S., Kytöviita, M.-M. & Tolvanen, A. 2011. Individual and combined effects of disturbance and N addition on understorey vegetation in a subarctic mountain birch forest. Journal of Vegetation Science 22: 262-272.
  • Olofsson, J., Ericson, L., Torp, M., Stark, S. & Baxter, R. 2011. Carbon fluxes under climate change influenced by disease mediated vegetation shifts. Nature Climate Change 1: 220-223.
  • Hilli, S., Stark, S. & Derome, J. 2010. Litter decomposition rates in relation to litter stocks in boreal coniferous forests along climatic and soil fertility gradients. Applied Soil Ecology 46: 200-208.
  • Martz, F., Jaakola, L., Julkunen-Tiitto, R. & Stark, S. 2010. Phenolic composition and antioxidant capacity of bilberry (Vaccinium myrtillus) leaves in Northern Europe following foliar development and along environmental gradients. Journal of Chemical Ecology 36(9): 1017-1028.
  • Stark, S., Männistö, M.K. & Smolander, A. 2010. Multiple effects of reindeer grazing on the soil processes in nutrient-poor northern boreal forests. Soil Biology & Biochemistry 42: 2068-2077.
  • Eskelinen, A., Stark, S. & Männistö, M. 2009. Links between plant community composition, soil organic matter quality and microbial communities in contrasting tundra habitats. Oecologia 161(1): 113-123.
  • Kytöviita, M.-M. & Stark, S. 2009. No allelopathic effect of the dominant forest-floor lichen Cladonia stellaris on pine seedlings. Functional Ecology 23: 435-441.
  • Rinnan, R., Stark, S. & Tolvanen, A. 2009. Responses of vegetation and soil microbial communities to warming and simulated herbivory in a subarctic heath. Journal of Ecology 97(4): 788-800.
  • Manninen, O., Stark, S., Kytöviita, M.-M., Lampinen, L. & Tolvanen, A. 2009. Understorey plant and soil responses to disturbance and increased nitrogen in boreal forests. Journal of Vegetation Science 20: 311-322.
  • Martz, F., Peltola, R., Fontanay, S., Duval, R., Julkunen-Tiitto, R. & Stark, S. 2009. Effect of latitutde and altitude on the terpenoid and soluble phenolic composition of juniper (Juniperus communis) needles and evaluation of their antibacterial activity in the boreal zone. Journal of Agricultural and Food Chemistry 57(20): 9575-9584.
  • Hilli, S., Stark, S. & Derome, J. 2008. Carbon quality and stocks in organic horizons in boreal forest soils. Ecosystems 11: 270-282.
  • Stark, S., Julkunen-Tiitto, R., Holappa, E., Mikkola, K. & Nikula, A. 2008. Concentrations of foliar quercetin in natural populations of white birch (Betula pubescens) increase with latitude. Journal of Chemical Ecology 34: 1382-1391.
  • Stark, S., Kytöviita, M.-M., Männistö, M. & Neumann, A.B. 2008. Soil microbial and microfaunal communities and organic matter quality in reindeer winter and summer ranges in Finnish subarctic mountain birch forests. Applied Soil Ecology 40: 456-464.
  • Stark, S., Julkunen-Tiitto, R. & Kumpula, J. 2007. Ecological role of reindeer summer browsing in the mountain birch (Betula pubescens ssp. czerepanovii) forests: effects on plant defense, litter decomposition, and soil nutrient cycling. Oecologia 151: 486-498.
  • Stark, S., Kytöviita, M.-M. & Neumann, A.B. 2007. The phenolic compounds in Cladonia lichens are not antimicrobial in soils. Oecologia 152: 299-306.