Aspen-associated mycorrhizal fungal production and respiration as a function of changing CO2, O3 and climatic variables

The relationships of mycorrhizal fungal respiration and productivity to climate and atmospheric chemistry remain under characterized. We quantified mycorrhizal sporocarp and hyphal respiration, as well as growing season net hyphal production, under ambient and elevated carbon dioxide (CO2) and ozone (O3) in relation to natural temperature and moisture variation. Hyphal respiration did not respond significantly to elevated CO2 and O3. Sporocarp respiration was affected by temperature and moisture content while hyphal respiratory response to temperature was undetected over the narrower range of soil temperatures captured. Hyphal respiration comprised 31 % of soil respiration, and the ratio of hyphal respiration to soil respiration declined with elevated CO2. Hyphal biomass was reduced under all treatments though not statistically significant. Given the large fraction of soil respiration represented by mycorrhizal fungi and its sensitivity to climate, a small change in fungal respiration could strongly affect carbon budgets and cycling under climate change.