Linking the respiration of fungal sporocarps with their nitrogen concentration: variation among species, tissues and guilds

Tissue nitrogen (N) concentration has been correlated with respiration (RS) across plants of different life-forms, functional and phylogenetic groups, plant organs and ectomycorrhizae of different fungal species. Nothing is known, however, if a similar relationship exists in other organisms like fungi. Here, we explored the N-RS relationship across sporocarps of 93 fungal species that varied in their guilds (mutualistic, saprotrophic and parasitic) as well as ‘tissue’ types (caps and stipes). We hypothesized that RS, N and protein concentrations were higher for saprotrophic fungi than for either mutualistic or parasitic fungi and were higher for caps than for stipes. We also hypothesized that respiration of fungal guild could be predicted by the N concentration. Lastly, we predicted N and RS were phylogenetically conserved and that by subtracting metabolically inactive N in chitin, we could improve the N-RS relationship. Sporocarp N concentration only explained 26% of the variation in RS across species. We found a significant difference in the N-RS relationship among the three fungal guilds, but no difference between the two tissue types. Saprotrophic species had higher N concentration and respiration than mutualistic and parasitic fungal species. Sporocarp components differed with caps showing both higher respiration and higher N and protein concentrations than stipes. Overall, our results show that fungal sporocarp nitrogen concentration is phylogenetically conserved among fungal families and may prove to be a strong predictor of fungal guild. The positive N-RS relationships existed for all fungal species (similar to plants), within fungal guilds (similar to plant functional groups), and fungal ‘tissue’ types (like plants’ organs). The clear linkage of fungal sporocarp respiration to total N concentration could help improve C and N cycling models in forest ecosystems by including estimates of fungal respiration based on fungal N concentration. A lay summary is available for this article.