Climate warming will change tundra plant communities via two main mechanisms: by altering performance of the local species and by enabling lowland and southern species immigration to open tundra. However, these mechanisms are not only driven by temperature, but their outcome can depend on other abiotic factors and biotic interactions in the system. We investigate interactive effects of climate warming, herbivores and nutrient availability on tundra plant communities and ecosystem functions.
I started this experiment as part of my PhD project in 2009 in collaboration with Dr. Anu Eskelinen and Dr. Johan Olofsson. The study site is an open tundra meadow in Kilpisjärvi, NW Finland. The main herbivores in the area are semi-domesticated reindeer, voles, lemmings, and mountain hares. The experiment consists of three treatments in a full factorial setting: 1) warming using open top chambers, 2) herbivore exclusion using fences against all mammalian herbivores, and 3) enhancement of nutrient availability using fertilizer.
We have shown that warming reduces species richness in absence of herbivores. Especially reindeer, which are the main herbivore in the area, limit success of tall and wide-leaved species and thereby enable survival of small tundra species.
Kaarlejärvi E, Eskelinen A & Olofsson J, 2017: Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains, Nature Communications 8: 419.
Currently we analyze how the treatment-induced plant community changes reflect to ecosystem functioning, such as carbon uptake, nutrient cycling, and composition of soil microbial communities. This is collaboration with Dr. Henni Ylänne, M.Sc. Coline Le Noir de Carlan and Dr. Erik Verbruggen.
Kaarlejärvi E, Eskelinen A, & Olofsson J, 2013: Herbivory prevents lowland plants benefiting from warmer and more fertile conditions at high altitudes. Functional Ecology, 27: 1244–1253.
Eskelinen A., Kaarlejärvi E. & Olofsson J, 2017: Herbivory and nutrient limitation protect warming tundra from lowland species’ invasion and diversity loss. Global Change Biology 23, 245–255.
Jessen M, Kaarlejärvi E, Olofsson J & Eskelinen A, 2020: Mammalian herbivory shapes intraspecific trait responses to warmer climate and nutrient enrichment. Global Change Biology 26: 6742-6752.