Temperature sensitivity of respiration differs among forest floor layers in a Pinus resinosa plantation

Abstract Decomposer microorganisms contribute to carbon loss from the forest floor as they metabolize organic substances and respire CO 2 . In temperate and boreal forest ecosystems, the temperature of the forest floor can fluctuate significantly on a day-to-night or day-to-day basis. In order to estimate total respiratory CO 2 loss over even relatively short durations, therefore, we need to know the temperature sensitivity ( Q 10 ) of microbial respiration. Temperature sensitivity has been calculated for microbes in different soil horizons, soil fractions, and at different depths, but we would suggest that for some forests, other ecologically relative soil portions should be considered to accurately predict the contribution of soil to respiration under warming. The floor of many forests is heterogeneous, consisting of an organic horizon comprising a few more-or-less distinct layers varying in decomposition status. We therefore determined at various measurement temperatures the respiration rates of litter, F-layer, and H-layer collected from a Pinus resinosa plantation, and calculated Q 10 values for each layer. Q 10 depended on measurement temperature, and was significantly greater in H-layer than in litter or F-layer between 5 and 17 °C. Our results indicate, therefore, that as the temperature of the forest floor rises, the increase in respiration by the H-layer will be disproportionate to the increase by other layers. However, change in respiration by the H-layer associated with change in temperature may contribute minimally or significantly to changes of total forest floor respiration in response to changes in temperature depending on the depth and thickness of the layer in different forest ecosystems.