Post-windthrow dynamics of soil CO2 efflux in mountainous forests of the Austrian Alps

Mathias Mayer1, Bradley Matthews1, Andreas Schindlbacher2, Klaus Katzensteiner1
1 Institute of Forest Ecology, BOKU
2 Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW)

O 2.11 in Environmental controls on fluxes and processes in ecosystems

17.07.2014, 15:30-15:50, H18

Catastrophic windthrows are known to cause long lasting effects on the carbon stocks and fluxes of forest ecosystems. Studies on the temporal dynamics of post-windthrow soil CO2 efflux in mountainous regions are however scarce. We therefore measured soil CO2 efflux in two windthrow affected mountain forest sites from 2009 until 2012. The sites were treated as a disturbance chronosequence, which consisted of intact control stands and windthrow areas that differed in years since disturbance. Combined with a direct time-series approach we could therefore investigate the temporal dynamics of soil CO2 efflux over 12 years post-windthrow. In comparison to the control stands no alterations in soil CO2 efflux could be proved for an initial period post-disturbance (1 to 6 years after disturbance), but significantly higher soil CO2 efflux rates were detected for a later period post-disturbance (9 to 12 years after disturbance). As soil temperature at the windthrow areas was on average 2.9 to 4.8 °C higher compared to the control stands, 20 to 36% of soil CO2 efflux at the windthrow areas could be attributed to warmer soil conditions. An increase in grass vegetation and a consequent increase in root respiration was assumed to contribute to the higher soil CO2 efflux in the later period post-disturbance. Annual estimates of 5 to 7 t C ha-1 yr-1 in the first years after windthrow suggest large losses of carbon to the atmosphere via soil CO2 efflux. We conclude that without active forest management to foster site regeneration (i.e. planting and protection from browsing), windthrow events can decrease soil carbon stocks and significantly weaken the carbon sink strength of forest sites of the Austrian Alps. This study was part of the INTERREG Bayern-Österreich 2007 -2013 project ‘SicAlp – Standortssicherung im Kalkalpin’ which was funded by the European Regional Development Fund (ERDF) and national funding.

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Letzte Änderung 19.06.2014