Higher Soil Respiration Rate Beneath Arbuscular Mycorrhizal Trees in a Northern Hardwood Forest is Driven by Associated Soil Properties
Soil respiration is the dominant pathway by which terrestrial carbon enters the atmosphere. Many abiotic and biotic processes can influence soil respiration, including soil microbial community composition. Mycorrhizal fungi are a particularly important microbial group because they are known to influence soil chemistry and nutrient cycling, and, because the type of mycorrhizal fungi in an ecosystem can be assessed based on the plant species present, they may be easier than other soil microbes to incorporate into ecosystem models. We tested how the type of mycorrhizal fungi—arbuscular (AM) or ectomycorrhizal (ECM) fungi—associated with the dominant tree species in a mixed hardwood forest was related to soil respiration rate. We measured soil respiration, root biomass, and surface area, and soil chemical and physical characteristics during the growing season in plots dominated by ECM-associated trees, AM-associated trees, and mixtures with both. We found rates of soil respiration that were 29% and 32% higher in AM plots than in ECM and mixed plots, respectively. These differences are likely explained by the slightly higher nitrogen concentrations and deeper organic horizons in soil within AM plots compared with soil in ECM and mixed plots. Our results highlight the importance of considering mycorrhizal associations of dominant vegetation as predictors of carbon cycling processes.
KeywordsSoil respiration Mycorrhizal fungi Carbon Microbial activity CO2 Northern hardwood forest
We thank Maanav Jalan and Alex Salazar for field assistance, and Brianna Hibner, Lacey Berg, Catherine D’Hennezel, Carolina Jimenez, Annalise Michaelson, and Sage Wentzell-Brehme for laboratory assistance. We appreciate the support of Geoff Wilson and Natalie Cleavitt in site selection. The Hubbard Brook Experimental Forest is administered by the US Department of Agriculture Forest Service, Northern Forest Research Station, Newtown Square, PA. The Hubbard Brook Long-Term Ecological Research site is funded by NSF award 1637685. Funding for this project was provided by Dartmouth College and the Wellesley College Office of the Provost.
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Conflict of interest
The authors declare that they have no conflict of interest.
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