Abstract
We used natural and tracer nitrogen (N) isotopes in a
Pinus taeda free air CO
2 enrichment (FACE) experiment to investigate functioning of ectomycorrhizal and saprotrophic fungi in N cycling. Fungal sporocarps were sampled in 2004 (natural abundance and
15N tracer) and 2010 (tracer) and δ
15N patterns were compared against litter and soil pools. Ectomycorrhizal fungi with hydrophobic ectomycorrhizas (e.g.
Cortinarius and
Tricholoma) acquired N from the Oea horizon or deeper. Taxa with hydrophilic ectomycorrhizas acquired N from the Oi horizon (
Russula and
Lactarius) or deeper (
Laccaria,
Inocybe, and
Amanita).
15N enrichment patterns for
Cortinarius and
Amanita in 2010 did not correspond to any measured bulk pool, suggesting that a persistent pool of active organic N supplied these two taxa. Saprotrophic fungi could be separated into those colonizing pine cones (
Baeospora), wood, litter (Oi), and soil (
Ramariopsis), with δ
15N of taxa reflecting substrate differences.
15N enrichment between sources and sporocarps varied across taxa and contributed to δ
15N patterns. Natural abundance and
15N tracers proved useful for tracking N from different depths into fungal taxa, generally corresponded to literature estimates of fungal activity within soil profiles, and provided new insights into interpreting natural abundance δ
15N patterns.
Keywords
15N,
carbon dioxide,
decomposition,
ectomycorrhizal fungi,
free air CO2 enrichment (FACE) experiment,
nitrogen (N) isotope,
organic nitrogen,
plant–microbial feedbacks
Citation
Hobbie, Erik A.; van Diepen, Linda T.A.; Lilleskov, Erik A.; Oiumette, Andrew P.; Finzi, Adrien C.; Hofmockel, Kirsten S. 2014. Fungal functioning in a pine forest: evidence from a
15N-labeled global change experiment. New Phytologist. 201(4): 1431-1439.