Ectomycorrhizal mycelia production in a forested peatland: effects on greenhouse gas fluxes

• The role of ectomycorrhizal fungi in key ecosystem processes such as C sequestration and greenhouse gas (GHG) fluxes is surprisingly poorly understood, even though they are undoubtedly of major significance. In this study we have measured the production and isotopic signature of extramatrical mycelium (EMM) of mycorrhizal fungi since 2007 using in-growth mesh bags. We also conducted a trenching experiment, where 50 µm (permit EMM but not roots) or 1 µm (excludes both EMM and roots) mesh was used. Soil respiration was measured using an automatic chamber system, and nitrous oxide (N2O) and methane (CH4) using a closed chamber technique. In general, the EMM production in the peat soil was low compared to other soils, but also varied much between years (from 0.03 to 4.09 g C m-2). The EMM production was also 2 to 6 times higher in the top 10 cm compared to 10-20 cm soil depth depending of year. Over the growing season the EMM production peaked in August, a few weeks before the main sporocarp season. The mycelial delta values also varied with several ‰ within season as well as between years. Interestingly, the δ15N but not the δ13C of the mycelia changed with depth and the differences relative to the SOM were inconsistent. Although the EMM production in the peat soil is low it had a major impact on GHG emissions from the soil. In 2009, the contribution from autotrophic mycelia respiration was 10% of the annual CO2 emissions, while autotrophic root respiration contributed with 23%. This means that 2/3 of the annual CO2 emissions are originated from heterotrophic respiration at this site. For N2O, the exclusion of roots alone did not affect N2O emissions, the simultaneous exclusion of roots and mycorrhizal mycelia doubled N2O emissions, compared to the control plots. The results of the study emphasize the importance of ectomycorrhiza in regulating GHG emissions from forested organic soils.

Subject headings

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

Boreal

Carbon

Ectomycorrhizae

Mycelia production

Greenhouse gases

Publication and Content Type

vet (subject category)

kon (subject category)