Decrease in heathland soil labile organic carbon under future atmospheric and climatic conditions

Characterization of the impacts of climate change on terrestrial carbon (C) cycling is important due to possible feedback mechanisms to atmospheric CO₂ concentrations. We investigated soil organic matter (SOM) dynamics in the A1 and A2 horizons (~ 0–5.1 and ~ 5.1–12.3 cm depth, respectively) of a sh...

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Bibliographic Details
Published in:Biogeochemistry 2017-03, Vol.133 (1), p.17-36
Main Authors: Thaysen, E. M., Reinsch, S., Larsen, K. S., Ambus, P.
Format: Article
Language:English
Subjects:
Atmospheric sciences
Biogeosciences
Carbon cycle
Carbon dioxide
Carbon sequestration
Climate change
Climatic conditions
Deschampsia flexuosa
Drought
Earth and Environmental Science
Earth Sciences
Ecosystems
Environmental Chemistry
Environmental conditions
Environmental impact
Life Sciences
Nitrogen
Organic carbon
Organic matter
Organic nitrogen
ORIGINAL PAPERS
Shrublands
Soil depth
Soil organic matter
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Summary:Characterization of the impacts of climate change on terrestrial carbon (C) cycling is important due to possible feedback mechanisms to atmospheric CO₂ concentrations. We investigated soil organic matter (SOM) dynamics in the A1 and A2 horizons (~ 0–5.1 and ~ 5.1–12.3 cm depth, respectively) of a shrubland grass (Deschampsia flexuosa) after 8 years of exposure to: elevated CO₂ (CO₂), summer drought (D), warming (T) and all combinations hereof, with TDCO₂ simulating environmental conditions for Denmark in 2075. The mean C residence time was highest in the heavy fraction (HF), followed by the occluded light fraction and the free light fraction (fLF), and it increased with soil depth, suggesting that C was stabilized on minerals at depth. A2 horizon SOM was susceptible to climate change whereas A1 horizon SOM was largely unaffected. The A2 horizon fLF and HF organic C stocks decreased by 43 and 23% in response to warming, respectively. Organic nitrogen (N) stocks of the A2 horizon fLF and HF decreased by 50 and 17%, respectively. Drought decreased the A2 horizon fLF N stock by 38%. Elevated CO₂ decreased the A2 horizon fLF C stock by 39% and the fLF N stock by 50%. Under TDCO₂, A2 horizon fLF C and N stocks decreased by 22 and 40%, respectively. Overall, our results indicate that shrubland SOM will be susceptible to increased turnover and associated net C and N losses in the future.
ISSN:0168-2563
1573-515X
DOI:10.1007/s10533-017-0303-3