Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard

Sammanfattning

Arctic tundra active-layer soils are at risk of soil organic carbon (SOC) depletion and degradation upon global climate warming because they are in a stage of relatively early decomposition. Non-growing season (NGS) warming is particularly pronounced, and observed increases of CO2 emissions during experimentally warmed NGSs give concern for great SOC losses to the atmosphere. Here, we used snow fences in Arctic Spitsbergen dwarf shrub tundra to simulate 1.86 degrees C NGS warming for 9 consecutive years, while growing season temperatures remained unchanged. In the snow fence treatment, the 4-11 cm thick A-horizon had a 2% lower SOC concentration and a 0.48 kg Cm-2 smaller pool size than the controls, indicating SOC pool depletion. The snow fence treatment's A-horizon's alkyl/O-alkyl ratio was also significantly increased, indicating an advance of SOC degradation. The underlying 5 cm of B/C-horizon did not show these effects. Our results support the hypothesis that SOC depletion and degradation are connected to the long-term transience of observed ecosystem respiration (ER) increases upon soil warming. We suggest that the bulk of warming induced ER increases may originate from surface and not deep active layer or permafrost horizons. The observed losses of SOC might be significant for the ecosystem in question, but are in magnitude comparatively small relative to anthropogenic greenhouse gas enrichment of the atmosphere. We conclude that a positive feedback of carbon losses from surface soils of Arctic dwarf shrub tundra to anthropogenic forcing will be minor, but not negligible. (C) 2018 Elsevier B.V. All rights reserved.

Nyckelord

Snow fence; NMR; Carbon loss; Decomposition; Anthropogenic C emission feedback; Tundra

Publicerad i

Science of the Total Environment
2019, volym: 646, sidor: 158-167
Utgivare: ELSEVIER SCIENCE BV

SLU författare

• Krab, Eveline

  • Institutionen för mark och miljö, Sveriges lantbruksuniversitet
    
  • Umeå Universitet

Globala målen (SDG)

SDG15 Ekosystem och biologisk mångfald

UKÄ forskningsämne

Markvetenskap
Miljövetenskap

Publikationens identifierare

• DOI: https://doi.org/10.1016/j.scitotenv.2018.07.150

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/96727