Saprotrophic and ectomycorrhizal fungal sporocarp stoichiometry (C†:†N†:†P) across temperate rainforests as evidence of shared nutrient constraints among symbionts

Summary: Quantifying nutritional dynamics of free-living saprotrophs and symbiotic ectomycorrhizal fungi (EMF) in the field is challenging, but the stoichiometry of fruiting bodies (sporocarps) may be an effective methodology for this purpose. Carbon (C), nitrogen (N), and phosphorus (P) concentrations of soils, foliage and 146 sporocarp collections were analyzed from 14 Pseudotsuga menziesii var. menziesii stands across a podzolization gradient on Vancouver Island (Canada). N and P concentrations were considerably higher in saprotrophic fungi. Fungal N% increased with soil N content at a greater rate for saprotrophs than EMF, while fungal P% of saprotrophs was more constrained. Fungal N:P was more responsive to soil N:P for EMF (homeostatic regulation coefficient ‘H’ =2.9) than saprotrophs (H= 5.9), while N:P of EMF and host tree foliage scaled almost identically. Results underscore the role of EMF as nutrient conduits, supporting host trees, whereas saprotrophs maintain a greater ...