How many times a day should gas fluxes be measured? By re-analyzing two datasets of
seasonal CH4 fluxes measured by an automated closed chamber system in Japan,Minamikawa et al. (2012) determined that measurements performed once per day during
mid-morning always resulted in acceptable estimates (i.e., ±10%) (Table 4.2). Therefore, we
recommend conducting measurements in mid-morning to obtain the daily mean CH4 flux. In
particular, in temperate parts of Asia, measurement at approximately 10:00 (09:00–11:00)
local mean time is recommended. The time window recommended here is consistent with
common practice (Sander and Wassmann, 2014). Although twice-per-day measurement can
improve trueness (Table 4.2), measurements in the early morning (when the plants may be
wet) and at night (when it is dark) in a rice paddy are not recommended. It should be noted
that the above analysis was conducted in fields in a temperate climate (in Japan), so further
investigation is required to determine the best schedule for fields in other climate regions
How many times a day should gas fluxes be measured? By re-analyzing two datasets ofseasonal CH4 fluxes measured by an automated closed chamber system in Japan,Minamikawa et al. (2012) determined that measurements performed once per day duringmid-morning always resulted in acceptable estimates (i.e., ±10%) (Table 4.2). Therefore, werecommend conducting measurements in mid-morning to obtain the daily mean CH4 flux. Inparticular, in temperate parts of Asia, measurement at approximately 10:00 (09:00–11:00)local mean time is recommended. The time window recommended here is consistent withcommon practice (Sander and Wassmann, 2014). Although twice-per-day measurement canimprove trueness (Table 4.2), measurements in the early morning (when the plants may bewet) and at night (when it is dark) in a rice paddy are not recommended. It should be notedthat the above analysis was conducted in fields in a temperate climate (in Japan), so furtherinvestigation is required to determine the best schedule for fields in other climate regions
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