Plant and soil nitrogen in oligotrophic boreal forest habitats with varying moss depths: does exclusion of large grazers matter?

Maria Väisänen, Maria Tuomi, Hannah Bailey, Jeffrey M. Welker

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The boreal forest consists of drier sunlit and moister-shaded habitats with varying moss abundance. Mosses control vascular plant–soil interactions, yet they all can also be altered by grazers. We determined how 2 decades of reindeer (Rangifer tarandus) exclusion affect feather moss (Pleurozium schreberi) depth, and the accompanying soil N dynamics (total and dissolvable inorganic N, δ 15N), plant foliar N, and stable isotopes (δ 15N, δ 13C) in two contrasting habitats of an oligotrophic Scots pine forest. The study species were pine seedling (Pinus sylvestris L.), bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), and feather moss. Moss carpet was deeper in shaded than sunlit habitats and increased with grazer exclusion. Humus N content increased in the shade as did humus δ 15N, which also increased due to exclusion in the sunlit habitats. Exclusion increased inorganic N concentration in the mineral soil. These soil responses were correlated with moss depth. Foliar chemistry varied due to habitat depending on species identity. Pine seedlings showed higher foliar N content and lower foliar δ 15N in the shaded than in the sunlit habitats, while bilberry had both higher foliar N and δ 15N in the shade. Thus, foliar δ 15N values of co-existing species diverged in the shade indicating enhanced N partitioning. We conclude that despite strong grazing-induced shifts in mosses and subtler shifts in soil N, the N dynamics of vascular vegetation remain unchanged. These indicate that plant–soil interactions are resistant to shifts in grazing intensity, a pattern that appears to be common across boreal oligotrophic forests.

Original languageEnglish
Pages (from-to)839-849
Issue number3
Publication statusPublished - 2 Jun 2021
MoEC publication typeA1 Journal article-refereed


  • Dwarf shrub
  • Inorganic nitrogen
  • Reindeer
  • δ C
  • δ N

Field of science

  • Ecology, evolutionary biology


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