Voles and lemmings are known for their high-amplitude population fluctuations and strong effects on dwarf shrub-dominated vegetation communities across the Fennoscandian tundra. Despite their key role in above-ground trophic interactions, there has been a dearth of research on how voles and lemmings affect ecosystem process rates, including ecosystem nutrient cycling and soil microbial activity. To address this gap, Maria Tuomi and colleagues studied how contrasting vole density regimes affect both vegetation and soil characteristics in a long-term island experiment located in West-Finnmark, Norway.
The study was conducted on the islands of Lake Iešjávri in West Finnmark, Norway
The study found that over the course of three population cycles, peak vole densities associated with increased abundance of palatable over non-palatable plants as well as increased nitrogen content in plant tissues. These changes in plant community characteristics link with increases in soil inorganic nitrogen content and microbial activity in litter. While these findings are in line with well-documented decimation of non-palatable shrubs during vole and lemming population peaks in Fennoscandia, they contrast predictions based on prevailing conceptual models on herbivore-plant-soil interactions. The study thus challenges the assumption that in low-productive ecosystems, herbivores slow down process rates by selectively eating nutritious plants, and proposes a new conceptual model with two alternative vole-plant-soil interaction pathways.
Reference: Tuomi, M., Stark, S., Hoset, K.S., Maria Väisänen, M., Oksanen, L., Murguzur, F.J.A., Tuomisto, H., Dahlgren, J., Bråthen, K.A. (2019) Herbivore effects on ecosystem process rates in a low-productive system. Ecosystems 22: 827-843
https://doi.org/10.1007/s10021-018-0307-4
Picture: In their study, high peak vole densities over multiple population cycles increased the relative abundance of forbs like Rubus chamaemorus (front) (photo: Maria Tuomi, University of Turku, 2018)