Fungal guild interactions slow decomposition of boreal forest pine litter and humus

Abstract

Ericaceous understory shrubs and ericoid mycorrhizal fungal communities are ubiquitous in boreal forests, and their interactions with ectomycorrhizal and saprotrophic fungi may determine organic matter dynamics in forest soils. We followed decomposition of pine needle litter and mor-layer humus over 3 yr in a factorial shrub removal- and pine root exclusion experiment in an old-growth Scots pine (Pinus sylvestris) forest, to evaluate effects of fungal guilds on mass loss. Litter mass loss was 23% greater when ectomycorrhizal fungi were excluded suggesting increased saprotrophic activity, independently of ericoid shrub presence. However, this 'Gadgil effect' was only found after 17 months following a summer drought. By contrast, humus mass loss was overall stimulated by ectomycorrhizal fungi, while ericoid mycorrhizal shrubs appeared to counteract this effect, potentially caused by simultaneous addition of recalcitrant organic matter and inhibition of ectomycorrhizal decomposers. We conclude that competitive saprotrophic-ectomycorrhizal fungal interactions may slow early-stage litter decomposition, but this effect was small and inconsistent. Furthermore, interactions between ecto- and ericoid mycorrhizal guild members appear to determine the late-stage organic matter balance of boreal forest humus.

Keywords

Bayesian modeling; Boreal forests; decomposition; ectomycorrhiza; ericoid mycorrhiza; Gadgil effect; saprotrophic fungi; soil

Published in

New Phytologist
2025
Publisher: WILEY

SLU Authors

• Mielke, Louis

  • Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
    
  • University of Stirling

• Klein, Julian

  • SLU Swedish Species Information Centre, Swedish University of Agricultural Sciences
    
  • Agroscope

• Finlay, Roger

  • Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
    

• Lindahl, Björn

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Clemmensen, Karina

  • Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science

Publication identifier

• DOI: https://doi.org/10.1111/nph.70316

Permanent link to this page (URI)

https://res.slu.se/id/publ/142946