Dependence of the Q10 values on the depth of the soil temperature measuring point

The parameter Q10 is commonly used to express the relationship between soil CO(2) efflux and soil temperature. One advantage of this parameter is its application in a model expression of respiration losses of different ecosystems. Correct specification of Q10 in these models is indispensable. Soil surface CO(2) efflux and soil temperature at different depths were measured in a 21-year-old Norway spruce stand and a mountain grassland site located at the Experimental Ecological Study Site Bily Kriz, Beskydy Mts. (NE Czech Republic), using automated gasometric systems. A time-delay and goodness-of-fit between soil CO(2) efflux and soil temperature at different measuring depths were determined. Wide ranges of values for the time-delay of CO(2) efflux in response to temperature, Q10 and the determination coefficient (R(2)) between CO(2) efflux and temperature were obtained at the both sites. The values of Q10 and the CO(2) time-delay increased with depth, while the R(2) of the CO(2)-temperature relationship significantly decreased. Soil temperature records obtained close to the soil surface showed the highest values of R(2) and the lowest value of the time-delay at both sites. Measurement of soil temperature at very shallow soil layer, preferably at the soil surface, is highly recommended to determine useable values of Q10. We present a new procedure to normalize Q10 values for soil temperatures measured at different depths that would facilitate comparison of different sites.