Ectomycorrhizal hydrophobicity and host association influence ectomycorrhizal C dynamics, N dynamics, and fruiting patterns in N addition experiments under pine

Background

Fungal traits such as host specificity and hydrophobicity of ectomycorrhizae may correspond to functional attributes including enzymatic capabilities, carbon (C) demand from host plants, temporal patterns of fruiting, C sequestration, and nitrogen (N) sequestration. Here, we assessed how these traits influenced the timing of C dynamics and fungal processing of C and N, as integrated by patterns of δ¹³C, δ¹⁵N, %N, and timing of ectomycorrhizal sporocarp production.

Methods

We linked these sporocarp patterns to ectomycorrhizal hydrophobicity, host specificity, and daily gross primary production (GPP) across seven N fertilization treatments in two Swedish Pinus sylvestris forests.

Results

GPP of eight and 7–10 days prior to collection correlated positively with δ¹³C and negatively with %N, respectively, for ~ 80% of sporocarps, reflecting transit times of peak delivery of plant-derived carbohydrates to sporocarp formation. Hydrophobic taxa fruited 7–10 days later than hydrophilic taxa and conifer-specific sporocarps averaged four days later than generalists. Hydrophobic taxa and conifer-specific taxa were higher in δ¹⁵N than hydrophilic taxa and generalist-associated taxa.

Conclusions

Higher δ¹⁵N and later sporocarp collections suggested greater C demands for hydrophobic and conifer-specific taxa than for hydrophilic and generalist taxa. C accumulation times and high sequestration (hydrophobic taxa, host-specific taxa) versus low sequestration (hydrophilic taxa, generalist taxa) of ¹⁵N-depleted chitin and ¹³C-enriched carbohydrates in mycelia could account for late fruiting, ¹⁵N enrichment, and ¹³C depletion of hydrophobic taxa. We conclude that sporocarp production, hydrophobicity, and host specificity integrated functional information about belowground hyphal development and C accumulation times of C transfers from host Pinus.