Sammanfattning

Nitrogen (N) deposition can change the carbon (C) sink of northern coniferous forests by changing the balance between net primary production and soil respiration. We used a field experiment in an N poor Pinus sylvestris forest where five levels of N (0, 3, 6, 12, and 50 kg N ha⁻¹ yr⁻¹, n = 6) had been added annually for 12–13 years to investigate how litter C inputs and soil respiration, divided into its autotrophic and heterotrophic sources, respond to different rates of N input, and its subsequent effect on soil C storage. The highest N addition rate (50 kg N ha⁻¹ yr⁻¹) stimulated soil C accumulation in the organic layer by 22.3 kg C kg⁻¹ N added, increased litter inputs by 46%, and decreased soil respiration per mass unit of soil C by 31.2%, mainly by decreasing autotrophic respiration. Lower N addition rates (≤ 12 kg N ha⁻¹ yr⁻¹) had no effect on litter inputs or soil respiration. These results support previous studies reporting on increased litter inputs coupled to impeded soil C mineralization, contributing to enhancing the soil C sink when N is supplied at high rates, but add observations for lower N addition rates more realistic for N deposition. In doing so, we show that litter production in N poor northern coniferous forests can be relatively unresponsive to low N deposition levels, that stimulation of microbial activity at low N additions is unlikely to reduce the soil C sink, and that high levels of N deposition enhance the soil C sink by increasing litter inputs and decreasing soil respiration.

Nyckelord

autotrophic respiration; boreal forest; carbon budget; carbon sequestration; heterotrophic respiration; nitrogen deposition; soil carbon poolsand fluxes; soil respiration

Publicerad i

Ecosystems
2020, Volym: 23, nummer: 7, sidor: 1423-1436

SLU författare

• Forsmark, Benjamin

  • Institutionen för skogens ekologi och skötsel, Sveriges lantbruksuniversitet
    

• Nordin, Annika

  • Institutionen för skoglig genetik och växtfysiologi, Sveriges lantbruksuniversitet
    

• Maaroufi, Nadia

  • Institutionen för skoglig mykologi och växtpatologi, Sveriges lantbruksuniversitet
    
  • Universität Bern

• Lundmark, Tomas

  • Institutionen för skogens ekologi och skötsel, Sveriges lantbruksuniversitet
    

• Gundale, Michael

  • Institutionen för skogens ekologi och skötsel, Sveriges lantbruksuniversitet
    

UKÄ forskningsämne

Markvetenskap


Publikationens identifierare

DOI: https://doi.org/10.1007/s10021-020-00478-8

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/106481