To what extent herbivores concomitantly alter silicon-based defence and nutrient levels in tundra grasses will ultimately determine changes in the quality of their pastures. In this study, we asked to what extent keystone tundra herbivores, small rodents and reindeer, affect silicon content and silicon:nutrient ratios of grasses found in tundra-grasslands.
Herbivores did not promote a net silicon accumulation in grasses, but rather enhanced their quality by increasing leaf nitrogen and phosphorus levels, thus decreasing silicon:nutrient ratios. Yet, the magnitude of these quality increments varied depending on the herbivore(s) involved and differed between inherently silicon-rich and silicon-poor grasses, ultimately leading to the formation of a fine-scale mosaic of tundra-patches with different nutrient values. In tundra-patches utilised by both herbivores, the quality of inherently silicon-rich grasses was further decreased relative to that of the already more palatable silicon-poor grasses. This could provide an advantage against herbivory, potentially being one of the pathways through which tundra-grassland vegetation states dominated by silicon-rich grasses are generally maintained by herbivores.
Reference: Petit Bon, M., Inga, K.G., Utsi, T.A., Jónsdóttir, I.S. and Bråthen, K.A. (2022), Forage quality in tundra grasslands under herbivory: Silicon-based defences, nutrients, and their ratios in grasses. Journal of Ecology 110(1): 129-143. https://doi.org/10.1111/1365-2745.13790
Text: Matteo Petit Bon, Czech Academy of Sciences.
Picture: The fence built in the 1950s at Ifjordfjellet, Finnmark, separates spring/fall migratory and summer pasture ranges for semi-domesticated reindeer (Photo: Matteo Petit-Bon).