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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 to investigate 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 at Hubbard Brook Experimental Forest in Woodstock, NH, USA. We found rates of soil respiration that were 29% and 32% higher in AM plots than in ECM and mixed plots, respectively. These differences were primarily explained by corresponding variation in soil conditions including organic horizon depth and soil nitrogen content. Soil in AM plots had slightly higher nitrogen concentrations and deeper organic horizons than soil in ECM and mixed plots. Our results highlight the importance of considering mycorrhizal associations of dominant vegetation as predictors of carbon cycling processes.

These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.