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Herbivory prevents positive responses of lowland plants to warmer and more fertile conditions at high altitudes
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Arcum)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Arcum)
2013 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 27, no 5, 1244-1253 p.Article in journal (Refereed) Published
Abstract [en]

Warm-adapted low elevation plants are expected to exhibit considerable range shifts to higher altitudes and latitudes as a result of climate warming and increased nutrient loads. However, empirical studies show that the magnitude and direction of plant responses are highly species- and site-specific, suggesting that several additional drivers interact with warmer climate.

We experimentally tested the interactive effects of climate warming, mammalian herbivory and soil fertility on low elevation plants. Seedlings of three warm-adapted lowland forbs (Epilobium angustifolium, Silene dioica and Solidago virgaurea) were transplanted to an open tundra site with native mountain tundra vegetation, and the effects of full factorial combinations of herbivore exclosures, warming and fertilization on transplant survival, growth and flowering were studied for two growing seasons. We also investigated the response of native vegetation biomass to the same treatments and compared it with the responses of transplanted lowland forbs.

Effects of both warming and fertilization on the transplanted lowland forbs strongly hinged on herbivore exclusion, resulting in 2–13-fold increase in biomass in warmed and fertilized plots without herbivores compared with warmed and fertilized plots with herbivores present, the magnitude depending on the species. While warm-adapted transplants benefited from warming, the native tundra plant community biomass did not respond to warming treatment.

Our results show that grazing limits the growth of transplants under warmer and more productive conditions, indicating that the expansion of lowland plant species to higher altitudes with warming may be hampered by mammalian herbivory. Furthermore, our results also suggest that migration of warm-adapted species into lightly grazed high-altitude tundra ecosystems might transform these communities to be more responsive to warmer climate and nutrient loads. Studies that do not consider species' upward shifts from lower altitudes might thus have underestimated vegetation responses to global warming, as well as the potential of herbivory to influence these responses.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013. Vol. 27, no 5, 1244-1253 p.
Keyword [en]
consumer control, global warming, grazing, range shift, reindeer, thermophilic plant, tundra, upward migration
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:umu:diva-79786DOI: 10.1111/1365-2435.12113ISI: 000325366500016OAI: diva2:644807
Available from: 2013-09-02 Created: 2013-09-02 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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