Evidence for the coupling of extraradical mycorrhizal hyphae production to plant C assimilation in Japanese warm-temperate forest of arbuscular mycorrhizal and ectomycorrhizal tree species

In temperate and boreal forest, the production of extraradical mycorrhizal hyphae (EMH) is a major pathway for the plant – soil carbon (C) flux. For warm-temperate forest, however, scarcely available field data provide inconclusive evidence for the drivers of EMH production dynamics. In this study, we measured the seasonal variation in EMH production in Japanese warm-temperate Chamaecyparis obtusa (arbuscular mycorrhizal evergreen) and Quercus serrata forest (ectomycorrhizal broad-leaf), and assessed the relationship of EMH production to air temperature, global solar radiation, and soil water content. EMH productions of six consecutive two-month periods were estimated from hyphal lengths (HLs) and hyphal carbon masses (HCs) in 360 hyphal in-growth mesh bags and corrected for non-mycorrhizal HLs and HCs in 72 control bags from root-trenched areas. Seasonal variations in HL and HC productions of EMH were significant in both forest types. HL and HC productions of EMH were significantly related to air temperature which drives plant C assimilation in both forest types. We, thus, present evidence for coupling of EMH production to plant C assimilation in warm-temperate forest, regardless of the dominating mycorrhizal type.