Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests?

Nasholm, T., Hogberg, P., Franklin, O. ORCID: https://orcid.org/0000-0002-0376-4140, Metcalfe, D., Keel, S.G., Campbell, C., Hurry, V., Linder, S., et al. (2013). Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests? New Phytologist 198 (1) 214-221. 10.1111/nph.12139.

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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 13CO2 absorbed through tree photosynthesis and 15N injected into a soil layer in which ectomycorrhizal fungi dominate the microbial community.

-- We detected little 15N 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.

Item Type: Article
Uncontrolled Keywords: Field experiment; 13C-15N pulse labelling; Modelling; Mycorrhiza; Nitrogen immobilization; Nitrogen limitation; Scots pine (Pinus sylvestris)
Research Programs: Ecosystems Services and Management (ESM)
Bibliographic Reference: New Phytologist; 198(1):214-221 (April 2013) (Published online 29 January 2013)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:49
Last Modified: 14 May 2019 08:52
URI: http://pure.iiasa.ac.at/10524

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