Abstract
Summary The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply, but how this affects fungal nutrition and growth remains to be clarified. We placed mesh‐bags with quartz sand, with or without an organic N ( 15 N‐, 13 C‐labeled) source, in the soil along a natural N supply gradient in boreal forest, to measure growth and use of N and C by ECM extramatrical mycelia. Mycelial C : N declined with increasing N supply. Addition of N increased mycelial growth at the low‐N end of the gradient. We found an inverse relationship between uptake of added N and C; the use of added N was high when ambient N was low, whereas use of added C was high when C from photosynthesis was low. We propose that growth of ECM fungi is N‐limited when soil N is scarce and tree belowground C allocation to ECM fungi is high, but is C‐limited when N supply is high and tree belowground C allocation is low. This suggests that ECM fungi have a major role in soil N retention in nutrient‐poor, but less so in nutrient‐rich boreal forests.
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Claims 7
Claim · model-written summary
Mycelial C:N declined with increasing N supply.
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e1“Mycelial C : N declined with increasing N supply”
Claim · model-written summary
Addition of N increased mycelial growth at the low-N end of the gradient.
- Taxon
- treee0
- Treatment
- Addition of Ne2
- Interactor
- ectomycorrhizal (ECM) fungie0symbiont
- Outcome
- mycelial growthe2
- Direction
- increasede2
- Setting
- low‐N end of the gradiente2
Not reportedComparator
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e2“Addition of N increased mycelial growth at the low‐N end of the gradient”
Claim · model-written summary
Uptake of added N and C by ECM mycelium was inversely related.
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e3“We found an inverse relationship between uptake of added N and C”
Claim · model-written summary
The use of added N by ECM mycelium was high when ambient N was low.
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e3“the use of added N was high when ambient N was low”
Claim · model-written summary
The use of added C by ECM mycelium was high when C from photosynthesis was low.
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e3“whereas use of added C was high when C from photosynthesis was low”
Claim · model-written summary
ECM fungal growth is proposed to be N-limited when soil N is scarce and C-limited when N supply is high.
Verbatim
e4“growth of ECM fungi is N‐limited when soil N is scarce and tree belowground C allocation to ECM fungi is high, but is C‐limited when N supply is high and tree belowground C allocation is low”
Claim · model-written summary
ECM fungi appear to have a major role in soil N retention in nutrient-poor but less so in nutrient-rich boreal forests.
Verbatim
e0“The supply of carbon (C) from tree photosynthesis to ectomycorrhizal (ECM) fungi is known to decrease with increasing plant nitrogen (N) supply”
e5“This suggests that ECM fungi have a major role in soil N retention in nutrient‐poor, but less so in nutrient‐rich boreal forests”