Grazing protects tundra plant diversity in a warming climate

Umeå/Oulu. Climate warming decreases number of plant species in tundra, but plant-eating animals, such as reindeer, can switch this negative effect to positive. The results by a Finnish-Swedish researcher team including also a researcher from UFZ/iDiv are published this week in Nature Communications. Findings by the researcher team show that grazers allow more plant species to grow together and benefit from warmer conditions by decreasing biomass of tall and wide-leaved plants and increasing light availability. The rate of climate warming is two to three times higher in the Arctic than the global average. Earlier studies suggest that tundra plant diversity will decrease in response to a warmer climate. However, it is important to know whether the response depends on the abundance of grazing animals, especially reindeer, voles and lemmings, which are common in tundra ecosystems. The researchers tested this by experimentally warming vegetation on tundra meadow with and without reindeer and voles. The researcher team found that warming increased species number in plots which were grazed, because it enabled small tundra plants to appear and grow there. But when reindeer, voles and lemmings were fenced out, vegetation became denser and more light limited, and as a result many small and slowly growing plant species were lost. “These results suggest that mammalian herbivores could in general help to protect diversity in warmer climate by preventing losses of small and slowly growing species”, says Anu Eskelinen, one of the team members, who is now working at the Helmholtz Centre for Environmental Research (UFZ) and German Centre for Integrative Biodiversity Research (iDiv). The study was done in Kilpisjärvi, NW Finland, where the researcher team tested during a 5-year field experiment the importance of grazing animals, warming and nutrient availability by combining small greenhouses that increased summer temperature by 1-2 degrees Celsius, small fences that excluded reindeer, voles and lemmings, and fertilization. The study site is a species-rich tundra meadow, dominated by grasses and forbs. Kilpisjärvi is an important area for semi-domesticated reindeer (Rangifer tarandus tarandus L.) in the summer. The research team includes Anu Eskelinen, who is Academy Research Fellow at University of Oulu, working currently at the Helmholtz Centre for Environmental Research (UFZ) and German Centre for Integrative Biodiversity Research (iDiv), Germany, Elina Kaarlejärvi (leading author) who is post-doctoral researcher at Climate Impact Research Centre (CIRC), Umeå University, but works currently at Vrije Universiteit Brussel in Belgium, and Johan Olofsson, associate professor at the Department of Ecology and Environmental Sciences and in CIRC at Umeå University. Publication:
Elina Kaarlejärvi, Anu Eskelinen and Johan Olofsson (2017): Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains. Nature Communications 8, Article number: 419. DOI: 10.1038/s41467-017-00554-z
http://dx.doi.org/10.1038/s41467-017-00554-z
The study was funded by grants from the JC Kempe Memorial Fund, Societas pro Fauna et Flora Fennica, Oskar Öflunds Stiftelse and Swedish Research Council, from the Academy of Finland and from the Nordic Centre of Excellence—Tundra and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning. The study has been supported by the TRY initiative on plant traits (http://www.try-db.org).For more information, contact: Anu Eskelinen, Academy research fellow, Helmholtz Centre for Environmental Research (UFZ) and German Centre for Integrative Biodiversity Research (iDiv), Germany, and Oulu University, Finland.
Tel: +49 1575 7756447
https://www.ufz.de/index.php?en=38880  & https://www.idiv.de/en/groups_and_people/employees/details/eshow/eskelinen_anu.htmlLinks: Reindeer grazing protects tundra plant diversity in a warming climate (Press Release from Umeå University) http://www.teknat.umu.se/english/about-the-faculty/news/newsdetailpage//reindeer-grazing-protects-tundra-plant-diversity-in-a-warming-climate.cid284829 Climate Impacts Research Centre (CIRC) / Umeå University https://www.arcticcirc.net/