Grazing protects tundra plant diversity in a warming climate

Climate warming decreases number of plant species in tundra, but plant-eating animals, such as reindeer and voles, can switch this negative effect to positive. The results by a Finnish-Swedish researcher team are published today 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.

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. Researchers from Umeå University, Sweden, and Oulu University, Finland, tested this by experimentally warming vegetation on tundra meadow with and without reindeer and voles.

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 researcher team members.

The study was done in Kilpisjärvi, NW Finland, where the researcher team tested 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 research team includes Anu Eskelinen, who is Academy Research Fellow at University of Oulu, working currently at Helmholtz Centre for Environmental Research and German Centre for Integrative Biodiversity Research, 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.

Kaarlejärvi, E., Eskelinen, A., Olofsson, J. (2017) Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains. Nature Communications, 8 (1), . doi:10.1038/s41467-017-00554-z https://www.nature.com/articles/s41467-017-00554-z

Photo: Anu Eskelinen

Last updated: 21.11.2017