Over the rice seasons of 2005, 2006 and 2007, the CH4 fluxes varied
from
−0.3 to 23.9 mg C m−2 h−1, and all the treatments showed
a comparable seasonality in CH4 fluxes (Fig. 3a–c). When the field
was waterlogged, the CH4 fluxes gradually increased from the
beginning of the measurement period until the seasonal peak fluxes
were attained at approximately 20–30 days after rice transplanting.
During the midseason drainage period, the CH4 fluxes dropped
sharply in all plots. Thereafter, they fluctuated according to the
alternating dry and wet conditions, which in turn were regulated
by intermittent irrigation. However, after reflooding of the fields a
strong recovery of CH4 fluxes was observed only during the 2007
rice season, whereas the corresponding CH4 fluxes during the 2005
and 2006 rice seasons remained at a lower level and increased only
slightly. It should be noted that the mitigation effect of the midseason
drainage on the CH4 fluxes was obvious for the 2005 and 2006
rice seasons but not for the 2007 rice season.
Over the rice seasons of 2005, 2006 and 2007, the CH4 fluxes variedfrom−0.3 to 23.9 mg C m−2 h−1, and all the treatments showeda comparable seasonality in CH4 fluxes (Fig. 3a–c). When the fieldwas waterlogged, the CH4 fluxes gradually increased from thebeginning of the measurement period until the seasonal peak fluxeswere attained at approximately 20–30 days after rice transplanting.During the midseason drainage period, the CH4 fluxes droppedsharply in all plots. Thereafter, they fluctuated according to thealternating dry and wet conditions, which in turn were regulatedby intermittent irrigation. However, after reflooding of the fields astrong recovery of CH4 fluxes was observed only during the 2007rice season, whereas the corresponding CH4 fluxes during the 2005and 2006 rice seasons remained at a lower level and increased onlyslightly. It should be noted that the mitigation effect of the midseasondrainage on the CH4 fluxes was obvious for the 2005 and 2006rice seasons but not for the 2007 rice season.
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