Mycorrhizal mycelial respiration: A substantial component of soil respired CO2

Mycorrhizal fungi constitute a considerable sink for plant photo-assimilates, yet poor knowledge about mycorrhizal mycelial respiration (RMyc) hinders the quantification of its role in belowground carbon cycling. We synthesized available field data of RMyc, and found that RMyc contributed 15% of soil respiration and 38% of autotrophic respiration (including RMyc and root respiration, RRoot). We observed no significant differences of RMyc between ectomycorrhiza and arbuscular mycorrhiza dominated ecosystems. Both RMyc/RRoot and RMyc/(RRoot + RMyc) significantly decreased with increasing RRoot, and correlated with absolute latitude, mean annual temperature and precipitation. Collectively, RMyc is a substantial component of soil respiration and exhibits divergent geographical pattern with that of RRoot, and should be considered separately in terrestrial carbon cycling models.