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Effects of warming on shrub abundance and chemistry drive ecosystem-level changes in a forest-tundra ecotone
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Arcum)
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2012 (English)In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 15, no 8, 1219-1233 p.Article in journal (Refereed) Published
Abstract [en]

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. © 2012 Springer Science+Business Media, LLC.

Place, publisher, year, edition, pages
2012. Vol. 15, no 8, 1219-1233 p.
Keyword [en]
CBSC, global warming, grazing, N, P, reindeer, secondary plant metabolite, shrub, treeline
National Category
Climate Research Ecology
URN: urn:nbn:se:umu:diva-63640DOI: 10.1007/s10021-012-9580-9OAI: diva2:582421
Available from: 2013-01-04 Created: 2013-01-03 Last updated: 2016-05-18Bibliographically approved
In thesis
1. The role of herbivores in mediating responses of tundra ecosystems to climate change
Open this publication in new window or tab >>The role of herbivores in mediating responses of tundra ecosystems to climate change
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Arctic areas are warming more rapidly than other parts of the world. Increasing temperatures are predicted to result in shrubification, higher productivity, declining species diversity and new species invasions to the tundra. Changes in species diversity and plant community composition are likely to alter ecosystem functions with potential consequences for human population also at lower latitudes. Thus, in order to better predict the effects of the rapid arctic warming, we need knowledge on how plant communities respond to a warmer climate. Here, I investigate the effects of climate warming on tundra plant communities and focus on the role of mammalian herbivores in mediating these responses. I examined the role of herbivores by incorporating herbivore manipulations to short- and long-term warming experiments as well as along altitudinal gradients. I measured how individual plants and plant communities respond to warming with and without herbivores.

Results of my PhD Thesis illustrate several ways how herbivores modify the responses of plants to warming. I found that herbivores (reindeer, hare, voles, lemmings) may prevent lowland forbs from invading open tundra.  Herbivores might also protect small tundra forbs from being outcompeted by taller and denser vegetation under climate warming. Thus, different herbivore pressures may lead to differing plant abundances and distribution shifts in different areas. Furthermore, my results show that high herbivore pressure can reverse the effects of long-term climate warming very rapidly, even in one year. This finding suggests that well-planned targeted reindeer grazing episodes could potentially be used as a conservation tool to keep selected tundra habitats open. Sudden cessation of grazing may initiate rapid changes in plant community, especially if it coincides with warm temperatures. Taken together, I show that herbivores counteract the effects of climate warming by slowing down or preventing vegetation changes in tundra. Therefore, it is important to consider mammalian herbivores when predicting tundra plant community responses to changing climate.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 23 p.
Climate change, warming, grazer, Rangifer, Lemmus lemmus, species distribution, biotic interactions, altitude
National Category
Research subject
biology, Environmental Science
urn:nbn:se:umu:diva-85208 (URN)978-91-7459-782-0 (ISBN)
Public defence
2014-02-21, KBC-huset, Stora hörsalen, KB3B1, Umeå universitet, Umeå, 10:00 (English)
Available from: 2014-01-31 Created: 2014-01-30 Last updated: 2014-01-30Bibliographically approved

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Kaarlejärvi, ElinaOlofsson, Johan
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