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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 21
Biogeosciences, 11, 6081–6093, 2014
https://doi.org/10.5194/bg-11-6081-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Climate extremes and biogeochemical cycles in the terrestrial...

Biogeosciences, 11, 6081–6093, 2014
https://doi.org/10.5194/bg-11-6081-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Nov 2014

Research article | 11 Nov 2014

Soil CO2 efflux from mountainous windthrow areas: dynamics over 12 years post-disturbance

M. Mayer1,*, B. Matthews1,*, A. Schindlbacher2, and K. Katzensteiner1 M. Mayer et al.
  • 1Institute of Forest Ecology, Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences – BOKU, Vienna, Austria
  • 2Department of Forest Ecology, Federal Research and Training Centre for Forests, Natural Hazards and Landscape – BFW, Vienna, Austria
  • *These authors contributed equally to this work.

Abstract. Windthrow-driven changes in carbon (C) allocation and soil microclimate can affect soil carbon dioxide (CO2) efflux (Fsoil) from forest ecosystems. Although Fsoil is the dominant C flux following stand-replacing disturbance, the effects of catastrophic windthrow on Fsoil are still poorly understood. We measured Fsoil at a montane mixed-forest site and at a subalpine spruce forest site from 2009 until 2012. Each site consisted of an undisturbed forest stand and two adjacent partially cleared (stem-fraction-harvested) windthrow areas, which differed with regard to the time since disturbance. The combination of chronosequence and direct time-series approaches enabled us to investigate Fsoil dynamics over 12 years post-disturbance. At both sites Fsoil rates did not differ significantly from those of the undisturbed stands in the initial phase after disturbance (1–6 years). In the later phase after disturbance (9–12 years), Fsoil rates were significantly higher than in the corresponding undisturbed stand. Soil temperature increased significantly following windthrow (by 2.9–4.8 °C), especially in the initial phase post-disturbance when vegetation cover was sparse. A significant part (15–31%) of Fsoil from the windthrow areas was attributed to the increase in soil temperature. According to our estimates, ~500–700 g C m−2 year−1 are released via Fsoil from south-facing forest sites in the Austrian Calcareous Alps in the initial 6 years after windthrow. With a high browsing pressure suppressing tree regeneration, post-disturbance net loss of ecosystem C to the atmosphere is likely to be substantial unless forest management is proactive in regenerating such sites. An increase in the frequency of forest disturbance by windthrow could therefore decrease soil C stocks and feed back positively on rising atmospheric CO2 concentrations.

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In this study soil CO2 efflux was measured at a montane mixed-forest site and a subalpine spruce forest site. Each site consisted of an undisturbed forest and two adjacent windthrow areas, differing regarding the time since disturbance. The combination of chronosequence and direct time-series approaches enabled us to investigate soil CO2 efflux dynamics over 12 years post-disturbance. According to our estimates, ~ 500 to 700 g C m-2 yr-1 are released via soil CO2 efflux from younger windthrows.
In this study soil CO2 efflux was measured at a montane mixed-forest site and a subalpine spruce...
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