Impacts of elevated CO 2 and temperature on soil respiration in warm temperate evergreen Quercus glauca stands: an open‐top chamber experiment

We conducted an open‐top chamber experiment for 3 years to examine the effect of elevated CO 2 and temperature on soil respiration in experimental stands of Quercus glauca , an evergreen tree species common in the warm temperate zone of Japan. Seedlings of Q. glauca were planted in open‐top chambers and treated with factorial combinations of ambient and elevated (ambient × 1.4, ambient × 1.8) CO 2 concentrations and ambient and elevated (+3°C) air temperatures. Elevated CO 2 significantly increased the total soil respiration rate ( P < 0.001) and the soil respiration rate at 15°C ( R 15 ) ( P < 0.05) but had no significant effect on the temperature coefficient Q 10 . Although temperature significantly affected total soil respiration rate ( P < 0.05), neither the R 15 nor the Q 10 of total soil respiration was affected significantly by the air temperature increase. Annual soil respiration rate, estimated from R 15 , Q 10 , and soil temperature data, tended to increase with elevated CO 2 concentration. These results suggest that soil respiration rate in Japanese warm temperate broad‐leaved forests dominated by Q. glauca is sensitive to elevated CO 2 and is likely to increase under future climatic conditions.