Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply
Bahn, Michael | Rodeghiero, Mirco | Anderson-Dunn, Margaret | Dore, Sabina | Gimeno, Cristina | Drösler, Matthias | Williams, Michael | Ammann, Christof | Berninger, Frank | Flechard, Chris | Jones, Stephanie | Balzarolo, Manuela | Kumar, Suresh | Newesely, Christian | Priwitzer, Tibor | Raschi, A. | Siegwolf, Rolf | Susiluoto, Sanna | Tenhunen, John | Wohlfahrt, Georg | Cernusca, Alexander
Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R s ( [graphic removed] ), R s at a reference soil temperature (10°C; [graphic removed] ) and annual R s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO₂ m⁻² s⁻¹, 0.3 to 5.5 μmol CO₂ m⁻² s⁻¹ and 58 to 1988 g C m⁻² y⁻¹, respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites [graphic removed] was closely related to [graphic removed] . Assimilate supply affected R s at timescales from daily (but not necessarily diurnal) to annual. Reductions of assimilate supply by removal of aboveground biomass through grazing and cutting resulted in a rapid and a significant decrease of R s. Temperature-independent seasonal fluctuations of R s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites [graphic removed] increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply overrides potential acclimation to prevailing temperatures. Also annual R s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate for deriving estimates of annual R s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight the importance of assimilate supply for soil CO₂ emissions at various timescales.
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