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Effects of Warming on Shrub Abundance and Chemistry Drive Ecosystem-Level Changes in a Forest-Tundra Ecotone

Kaarlejärvi, E.; Baxter, R.; Hofgaard, A.; Hytteborn, H.; Khittun, O.; Molau, U.; Sjögersten, S.; Wookey, P.; Olofsson, J.

Effects of Warming on Shrub Abundance and Chemistry Drive Ecosystem-Level Changes in a Forest-Tundra Ecotone Thumbnail


Authors

E. Kaarlejärvi

A. Hofgaard

H. Hytteborn

O. Khittun

U. Molau

S. Sjögersten

P. Wookey

J. Olofsson



Abstract

Tundra vegetation is responding rapidly to on-going climate warming. The changes in plant abundance and chemistry might have cascading effects on tundra food webs, but an integrated understanding of how the responses vary between habitats and across environmental gradients is lacking. We assessed responses in plant abundance and plant chemistry to warmer climate, both at species and community levels, in two different habitats. We used a long-term and multisite warming (OTC) experiment in the Scandinavian forest–tundra ecotone to investigate (i) changes in plant community composition and (ii) responses in foliar nitrogen, phosphorus, and carbon-based secondary compound concentrations in two dominant evergreen dwarf-shrubs (Empetrum hermaphroditum and Vaccinium vitis-idaea) and two deciduous shrubs (Vaccinium myrtillus and Betula nana). We found that initial plant community composition, and the functional traits of these plants, will determine the responsiveness of the community composition, and thus community traits, to experimental warming. Although changes in plant chemistry within species were minor, alterations in plant community composition drive changes in community-level nutrient concentrations. In view of projected climate change, our results suggest that plant abundance will increase in the future, but nutrient concentrations in the tundra field layer vegetation will decrease. These effects are large enough to have knock-on consequences for major ecosystem processes like herbivory and nutrient cycling. The reduced food quality could lead to weaker trophic cascades and weaker top down control of plant community biomass and composition in the future. However, the opposite effects in forest indicate that these changes might be obscured by advancing treeline forests.

Citation

Kaarlejärvi, E., Baxter, R., Hofgaard, A., Hytteborn, H., Khittun, O., Molau, U., …Olofsson, J. (2012). Effects of Warming on Shrub Abundance and Chemistry Drive Ecosystem-Level Changes in a Forest-Tundra Ecotone. Ecosystems, 15(8), 1219-1233. https://doi.org/10.1007/s10021-012-9580-9

Journal Article Type Article
Publication Date Dec 1, 2012
Deposit Date Dec 6, 2013
Publicly Available Date Sep 18, 2014
Journal Ecosystems
Print ISSN 1432-9840
Electronic ISSN 1435-0629
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 15
Issue 8
Pages 1219-1233
DOI https://doi.org/10.1007/s10021-012-9580-9
Keywords Treeline, Reindeer, Shrub, Global warming, Grazing, Secondary plant metabolite, CBSC, N, P.

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