Hubbard Brook Experimental Forest: Soil respiration in mycorrhizal gradient plots

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.