The bottom rim
of the chamber was inserted about 3 cm into the surface
soil. Its top cover was sealed and about 0.5 L of the air in
the headspace was collected at a 20-minute interval to
determine the CO2 concentration by an infrared gas
analyzer (IRGA) (ZFP5, Fuji Electronics Co. Ltd, Japan).
Measurements were performed mostly from 9 a.m. to 2
p.m