Components explain, but do eddy fluxes constrain? Carbon budget of a nitrogen-fertilized boreal Scots pine forest

Abstract

• Nitrogen (N) fertilization increases biomass and soil organic carbon (SOC) accumulation in boreal pine forests, but the underlying mechanisms remain uncertain. At two Scots pine sites, one undergoing annual N fertilization and the other a reference, we sought to explain these responses.
• We measured component fluxes, including biomass production, SOC accumulation, and respiration, and summed them into carbon budgets. We compared the resulting summations to ecosystem fluxes measured by eddy covariance.
• N fertilization increased most component fluxes (P < 0.05), especially SOC accumulation (20×). Only fine-root, mycorrhiza, and exudate production decreased, by 237 (SD = 28) g C m⁻² yr⁻¹. Stemwood production increases were ascribed to this partitioning shift, gross primary production (GPP), and carbon-use efficiency, in that order. The methods agreed in their estimates of GPP in both stands (P > 0.05), but the components detected an increase in net ecosystem production (NEP) (190 (54) g C m⁻² yr⁻¹; P < 0.01) that eddy covariance did not (19 (62) g C m⁻² yr⁻¹; ns).
• The pairing of plots, the simplicity of the sites, and the strength of response provide a compelling description of N effects on the C budget. However, the disagreement between methods calls for further paired tests of N fertilization effects in simple forest ecosystems.

Keywords

canopy photosynthesis; carbon flux partitioning; carbon sequestration; carbon-use efficiency; eddy covariance; nitrogen fertilization

Published in

New Phytologist
2023, volume: 239, number: 6, pages: 2166-2179
Publisher: WILEY

SLU Authors

• Marshall, John

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Tarvainen, Lasse

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • University of Gothenburg

• Zhao, Peng

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Lim, Hyungwoo

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • University of Tartu

• Näsholm, Torgny

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Lundmark, Tomas

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Linder, Sune

  • Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences
    

• Peichl, Matthias

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science
Soil Science

Publication identifier

• DOI: https://doi.org/10.1111/nph.18939

Permanent link to this page (URI)

https://res.slu.se/id/publ/122322