Long-term aboveground and belowground consequences of red wood ant exclusion in boreal forest

David A. Wardle, Fujio Hyodo, Richard D. Bardgett, Gregor W. Yeates, Marie Charlotte Nilsson

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)

Abstract

Despite their ubiquity, the role of ants in driving ecosystem processes both aboveground and belowground has been seldom explored, except within the nest. During 1995 we established 16 ant exclusion plots of approximately 1.1 3 1.1 m, together with paired control plots, in the understory layer of a boreal forest ecosystem in northern Sweden that supports high densities of the mound-forming ant Formica aquilonia, a red wood ant species of the Formica rufa group. Aboveground and belowground measurements were then made on destructively sampled subplots in 2001 and 2008, i.e., 6 and 13 years after set-up. While ant exclusion had no effect on total understory plant biomass, it did greatly increase the relative contribution of herbaceous species, most likely through preventing ants from removing their seeds. This in turn led to higher quality resources entering the belowground subsystem, which in turn stimulated soil microbial biomass and activity and the rates of loss of mass and carbon (C) and nitrogen (N) from litter in litterbags placed in the plots. This was accompanied by losses of ;15% of N and C stored in the humus on a per area basis. Ant exclusion also had some effects on foliar stable isotope ratios for both C and N, most probably as a consequence of greater soil fertility. Further, exclusion of ants had multitrophic effects on a microbe- nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web. Our results point to a major role of red wood ants in determining forest floor vegetation and thereby exerting wide-ranging effects on belowground properties and processes. Given that the boreal forest occupies 11% of the Earth's terrestrial surface and stores more C than any other forest biome, our results suggest that this role of ants could potentially be of widespread significance for biogeochemical nutrient cycling, soil nutrient capital, and sequestration of belowground carbon.

Original languageEnglish
Pages (from-to)645-656
Number of pages12
JournalEcology
Volume92
Issue number3
DOIs
Publication statusPublished - Mar 1 2011

Keywords

  • Boreal forest
  • Carbon sequestrationdecomposition
  • Exclusion experiments
  • Formica aquilonia
  • Formica rufa group
  • Red wood ants
  • Soil food web
  • Understory vegetation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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