The apparent temperature response of leaf respiration depends on the timescale of measurements: A study of two cold climate species

Productivity and climate models often use a constant Q₁₀ for plant respiration, assuming tight control of respiration by temperature. We studied the temperature response of leaf respiration of two cold climate species (the Australian tree Eucalyptus pauciflora and the subantarctic megaherb Pringlea antiscorbutica, both measured in a field setting) on a short timescale (minutes) during different times within a diel course, and on a longer timescale, using diel variations in ambient temperature. There were great variations in Q₁₀ depending on measuring day, measuring time and measuring method. When Q₁₀ was calculated from short-term (15 min) manipulations of leaf temperature, the resulting values were usually markedly smaller than when Q₁₀ was calculated from measurements at ambient leaf temperatures spread over a day. While for E. pauciflora, Q₁₀ estimates decreased with rising temperature (corroborating the concept of a temperature-dependent Q₁₀), the opposite was the case for P. antiscorbutica. Clearly, factors other than temperature co-regulate both leaf respiration rates and temperature sensitivity and contribute to diel and seasonal variation of respiration.