Atmospheric nitrogen enrichment changes nutrient stoichiometry and reduces fungal N supply to peatland ericoid mycorrhizal shrubs

Vesala, Risto; Kiheri, Heikki; Hobbie, Erik A.; van Dijk, Netty; Dise, Nancy; Larmola, Tuula

Atmospheric nitrogen enrichment changes nutrient stoichiometry and reduces fungal N supply to peatland ericoid mycorrhizal shrubs

Vesala, Risto; Kiheri, Heikki; Hobbie, Erik A.; van Dijk, Netty; Dise, Nancy ORCID: https://orcid.org/0000-0003-0463-6885; Larmola, Tuula. 2021 Atmospheric nitrogen enrichment changes nutrient stoichiometry and reduces fungal N supply to peatland ericoid mycorrhizal shrubs. Science of the Total Environment, 794, 148737. 10, pp. 10.1016/j.scitotenv.2021.148737

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Official URL: http://dx.doi.org/10.1016/j.scitotenv.2021.148737

Abstract/Summary

Peatlands store one third of global soil carbon (C) and up to 15% of global soil nitrogen (N) but often have low plant nutrient availability owing to slow organic matter decomposition under acidic and waterlogged conditions. In rainwater-fed ombrotrophic peatlands, elevated atmospheric N deposition has increased N availability with potential consequences to ecosystem nutrient cycling. Here, we studied how 14 years of continuous N addition with either nitrate or ammonium had affected ericoid mycorrhizal (ERM) shrubs at Whim Bog, Scotland. We examined whether enrichment has influenced foliar nutrient stoichiometry and assessed using N stable isotopes whether potential changes in plant nutrient constraints are linked with plant N uptake through ERM fungi versus direct plant uptake. High doses of ammonium alleviated N deficiency in Calluna vulgaris and Erica tetralix, whereas low doses of ammonium and nitrate improved plant phosphorus (P) nutrition, indicated by the lowered foliar N:P ratios. Root acid phosphatase activities correlated positively with foliar N:P ratios, suggesting enhanced P uptake as a result of improved N nutrition. Elevated foliar δ15N of fertilized shrubs suggested that ERM fungi were less important for N supply with N fertilization. Increases in N availability in peat porewater and in direct nonmycorrhizal N uptake likely have reduced plant nitrogen uptake via mycorrhizal pathways. As the mycorrhizal N uptake correlates with the reciprocal C supply from host plants to the soil, such reduction in ERM activity may affect peat microbial communities and even accelerate C loss via decreased ERM activity and enhanced saprotrophic activity. Our results thus introduce a previously unrecognized mechanism for how anthropogenic N pollution may affect nutrient and carbon cycling within peatland ecosystems.

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.scitotenv.2021.148737

UKCEH and CEH Sections/Science Areas:

Atmospheric Chemistry and Effects (Science Area 2017-24)
UKCEH Fellows

ISSN:

0048-9697

Additional Information:

Open Access paper - full text available via Official URL link.

Additional Keywords:

ombrotrophic bogs, nitrogen deposition, nitrate, ammonium, phosphorus, stable isotopes