The carbon sequestration response of aboveground biomass and soils to nutrient enrichment in boreal forests depends on baseline site productivity

Abstract

Nutrient enrichment can alleviate productivity limitations and thus substantially increase carbon (C) uptake in northern coniferous forests. Yet, factors controlling stand-to-stand variation of forest ecosystem responses to nutrient enrichment remain unclear. We used five long-term (13 years) nutrient-enrichment experiments across Sweden, where nitrogen (N), phosphorus, and potassium were applied annually to young Norway spruce forests that varied in their baseline ecosystem properties. We measured tree biomass and soil C and N stocks, litterfall C inputs, soil CO2 efflux, and shifts in composition and biomass of soil microbial communities to understand the links between above and belowground responses to nutrient enrichment. We found that the strongest responses in tree biomass occurred when baseline site productivity was lowest. High increases in tree biomass C stocks were generally balanced by weaker responses in organic soil C stocks. The average ecosystem C-N response rate was 35 kg C kg-1 N added, with a nearly five-fold greater response rate in tree biomass than in soil. The positive nutrient enrichment effects on ecosystem C sinks were driven by a 95% increase in tree biomass C stocks, 150% increase in litter production, 67% increase in organic layer C stocks, and a 46% reduction in soil CO2 efflux accompanied by compositional changes in soil microbial communities. Our results show that ecosystem C uptake in spruce forests in northern Europe can be substantially enhanced by nutrient enrichment; however, the strength of the responses and whether the enhancement occurs mainly in tree biomass or soils are dependent on baseline forest productivity.

Keywords

Ecosystem carbon stocks; Soil carbon; Soil nitrogen; Litterfall; Soil respiration; Soil microbial community

Published in

Science of the Total Environment
2022, volume: 838, article number: 156327
Publisher: ELSEVIER

SLU Authors

• Blasko, Robert

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

• Forsmark, Benjamin

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

• Gundale, Michael

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

• Lim, Hyungwoo

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

• Lundmark, Tomas

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

• Nordin, Annika

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

Associated SLU-program

SLU Plant Protection Network
SLU Forest Damage Center

Global goals (SDG)

SDG15 Life on land

UKÄ Subject classification

Environmental Sciences
Ecology
Forest Science

Publication identifier

• DOI: https://doi.org/10.1016/j.scitotenv.2022.156327

Permanent link to this page (URI)

https://res.slu.se/id/publ/118343