Fulltext

Experimental summer drought reduces soil CO2 effluxes and DOC leaching in Swiss grassland soils along an elevational gradient

Hagedorn, Frank ; Joos, Ottmar

In: Biogeochemistry, 2014, vol. 117, no. 2-3, p. 395-412

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    Titel
    • Experimental summer drought reduces soil CO2 effluxes and DOC leaching in Swiss grassland soils along an elevational gradient
    Autor
    • Hagedorn, Frank. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
    • Joos, Ottmar. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
    Dokumententyp
    • Postprint
    Sprache
    • Englisch
    Veröffentlicht in
    • Biogeochemistry, 2014, vol. 117, no. 2-3, p. 395-412. Springer International Publishing
    Andere elektronische Ausgabe
    OAI-PMH-ID
    • oai:doc.rero.ch:326581
    Summary
    Soil moisture affects belowground activity in grasslands, but the effects of summer drought on different soil C fluxes is uncertain. Soil respiration (SR), dissolved organic carbon (DOC) leaching and their components may all respond differently and drought effects will interact with other factors such as temperature, making a priori predictions of soil C balances difficult. In this study, we used rain shelters to simulate summer droughts by reducing annual precipitation by around 30% in three managed grassland sites at 400, 1,000 and 2,000m a.s.l. in Switzerland covering a gradient in mean annual temperatures of 7.5°C. During the growing season, we quantified the impacts of drought on SR, DOC leaching, litter decomposition and the contribution of 13C-depleted litter to DOC fluxes. Along the elevational gradient, SR rates did not decrease with increasing altitude. Thus, SR was higher at a given temperature at higher altitudes, which probably reflects more labile soil C and hence greater substrate availability in a colder climate. Fluxes of DOC at 5cm depth were a magnitude smaller than SR and did not show a pattern with elevation. At all altitudes, the experimental summer drought significantly reduced SR rates by 25-57% and DOC leaching by 80-100%, with a declining contribution of 13C-depleted litter-DOC. The remaining litter mass after drought was two to seven times larger as compared to the control. We did not observe a strong C release upon rewetting and hence, there was no compensation for the reduced soil C fluxes during drought. The more sensitive drought response in the litter layer than in the deeper soil and the declining DOC fluxes indicate an altered soil C balance with a C preservation in the topsoil, but ongoing losses of probably ‘older' C in subsoils under drought.