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- Title
Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests?
- Authors
Näsholm, Torgny; Högberg, Peter; Franklin, Oskar; Metcalfe, Daniel; Keel, Sonja G.; Campbell, Catherine; Hurry, Vaughan; Linder, Sune; Högberg, Mona N.
- Abstract
Symbioses between plant roots and mycorrhizal fungi are thought to enhance plant uptake of nutrients through a favourable exchange for photosynthates. Ectomycorrhizal fungi are considered to play this vital role for trees in nitrogen (N)-limited boreal forests., We followed symbiotic carbon ( C)- N exchange in a large-scale boreal pine forest experiment by tracing 13 CO2 absorbed through tree photosynthesis and 15 N injected into a soil layer in which ectomycorrhizal fungi dominate the microbial community., We detected little 15 N in tree canopies, but high levels in soil microbes and in mycorrhizal root tips, illustrating effective soil N immobilization, especially in late summer, when tree belowground C allocation was high. Additions of N fertilizer to the soil before labelling shifted the incorporation of 15N from soil microbes and root tips to tree foliage., These results were tested in a model for C- N exchange between trees and mycorrhizal fungi, suggesting that ectomycorrhizal fungi transfer small fractions of absorbed N to trees under N-limited conditions, but larger fractions if more N is available. We suggest that greater allocation of C from trees to ectomycorrhizal fungi increases N retention in soil mycelium, driving boreal forests towards more severe N limitation at low N supply.
- Subjects
ECTOMYCORRHIZAL fungi; TREE growth; NITROGEN in soils; TAIGAS; MYCORRHIZAS; SCOTS pine
- Publication
New Phytologist, 2013, Vol 198, Issue 1, p214
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/nph.12139