Annual and seasonal variations of Q10 soil respiration in the sub-alpine forests of the Eastern Qinghai-Tibet Plateau, China

The annual and seasonal variations in the temperature sensitivity of soil respiration (Rs) were assessed through continuous measurements during the 2004-2006 growing seasons using chamber-based techniques in two sub-alpine forest ecosystems in the Eastern Qinghai-Tibet Plateau, China. The study sites were 40-year-old spruce plantations (Picea asperata) (FSPF) and Faxon Fir Primary Forest (FPF). Our results showed that Q10, regardless of site origin, exhibited a strong seasonal and annual variation pattern, and decreased with soil temperature increase. Estimated Q10 values ranged between 1.16 and 24.3. The maximum, annual, mean Q10 values remained consistent over 3 years, while the highest Q10 values (7.01 in FSPF and 6.39 in FPF) occurred in 2005 (for all sites). There was no significant difference observed among Q10 values between the two forest types in each year (2004-2006) (p = 0.07). Q10 values were fitted well with data of soil temperature using linear regression models, while the correlation between Q10 and soil moisture was not significant (p > 0.1). This study suggested that soil temperature was the dominant factor influencing Q10 values, while soil moisture was a potential contributor to the annual and seasonal variations of Q10 in a sub-alpine forest. Due to the complexity of correlation between Rs and soil moisture, Q10 values derived from annual and seasonal patterns of RS should be used with caution when predicting future soil CO2 emissions under conditions of global warming.