Understanding how plant tissue respiration will adjust to a changing climate will help us correctly model future ecosystem respiration and carbon balance. Exponential increases in root system respiration with temperature could lead to much greater CO₂ efflux to the atmosphere, creating a positive feedback loop leading to enhanced warming. This could also reduce C availability for biomass production. The objective of this study is to determine how fine root respiration of woody perennials will respond to warmer soils and if acclimation will occur in the short-term (weeks to months) in response to elevated soil temperature. Fine root (<1 mm) respiration was measured in an Acer saccharum dominated northern hardwood forest throughout the summer of 2009 to determine if the root respiration would acclimate to seasonal changes in temperature. In mid-summer of 2010, a soil warming experiment will be initiated at the study location with treatments including: control, warming (+3 deg), water (ambient precipitation + 20%) and warming with water. In 2009, specific root respiration rates were measured monthly from May to November at ambient soil temperatures for the sample date, and at a common reference temperature of 18°C. Comparing specific root respiration rates at a common reference temperature across different dates is a good indicator for the presence of acclimation.

Results/Conclusions

Measurements made at ambient soil temperature during the summer of 2009 indicated root respiration increased exponentially with temperature (Q₁₀ = 2.4). Respiration rates at the constant reference temperature did not decrease with increasing seasonal soil temperatures, which would have been expected if significant seasonal acclimation was present. Experimental warming will be initiated in the summer of 2010 and we will compare the pretreatment responses to the experimental warming responses to assess the presence of acclimation of root respiration to the consistently increased temperatures.