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Empirical and Earth system model estimates of boreal nitrogen fixation often differ: A pathway toward reconciliation

Hupperts, Stefan and Gerber, Stefan and Nilsson Hegethorn, Marie-Charlotte and Gundale, Michael (2021). Empirical and Earth system model estimates of boreal nitrogen fixation often differ: A pathway toward reconciliation. Global Change Biology. 27 , 5711-5725
[Article Review/Survey]

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Abstract

The impacts of global environmental change on productivity in northern latitudes will be contingent on nitrogen (N) availability. In circumpolar boreal ecosystems, nonvascular plants (i.e., bryophytes) and associated N-2-fixing diazotrophs provide one of the largest known N inputs but are rarely accounted for in Earth system models. Instead, most models link N-2-fixation with the functioning of vascular plants. Neglecting nonvascular N-2-fixation may be contributing toward high uncertainty that currently hinders model predictions in northern latitudes, where nonvascular N-2-fixing plants are more common. Adequately accounting for nonvascular N-2-fixation and its drivers could subsequently improve predictions of future N availability and ultimately, productivity, in northern latitudes. Here, we review empirical evidence of boreal nonvascular N-2-fixation responses to global change factors (elevated CO2, N deposition, warming, precipitation, and shading by vascular plants), and compare empirical findings with model predictions of N-2-fixation using nine Earth system models. The majority of empirical studies found positive effects of CO2, warming, precipitation, or light on nonvascular N-2-fixation, but N deposition strongly downregulated N-2-fixation in most empirical studies. Furthermore, we found that the responses of N-2-fixation to elevated CO2 were generally consistent between models and very limited empirical data. In contrast, empirical-model comparisons suggest that all models we assessed, and particularly those that scale N-2-fixation with net primary productivity or evapotranspiration, may be overestimating N-2-fixation under increasing N deposition. Overestimations could generate erroneous predictions of future N stocks in boreal ecosystems unless models adequately account for the drivers of nonvascular N-2-fixation. Based on our comparisons, we recommend that models explicitly treat nonvascular N-2-fixation and that field studies include more targeted measurements to improve model structures and parameterization.

Authors/Creators:Hupperts, Stefan and Gerber, Stefan and Nilsson Hegethorn, Marie-Charlotte and Gundale, Michael
Title:Empirical and Earth system model estimates of boreal nitrogen fixation often differ: A pathway toward reconciliation
Series Name/Journal:Global Change Biology
Year of publishing :2021
Volume:27
Page range:5711-5725
Number of Pages:15
Publisher:WILEY
ISSN:1354-1013
Language:English
Publication Type:Article Review/Survey
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Climate Research
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
Keywords:boreal, bryophyte, diazotroph, Earth system model, elevated CO2, nitrogen deposition, nitrogen fixation, nonvascular
URN:NBN:urn:nbn:se:slu:epsilon-p-113455
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-113455
Additional ID:
Type of IDID
DOI10.1111/gcb.15836
Web of Science (WoS)000686962800001
ID Code:25945
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:25 Oct 2021 08:45
Metadata Last Modified:25 Oct 2021 08:51

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