Comparison of Daytime and Nighttime Ecosystem Respiration Measured by the Closed Chamber Technique on a Temperate Mire in Poland
Radosław Juszczak1,2, Manuel Acosta3,4, Janusz Olejnik1,4
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1Meteorology Department, Poznan University of Life Sciences, Piątkowska 94, 60-649 Poznań, Poland
2Institute for Agricultural and Forest Environment, Polish Academy of Science, Bukowska 19, 60-809 Poznań, Poland
3Department of Physics, Division of Atmospheric Sciences, FI-00014 University of Helsinki, Finland
4Department of Matter and Energy Fluxes, Global Change Research Center, AS CR, v.v.i. Brno, Czech Republic
Pol. J. Environ. Stud. 2012;21(3):643–658
Ecosystem respiration (Reco) plays an important role in estimating the global carbon balance of terrestrial ecosystems, and knowledge of respiration is required to correctly assess the gross primary (GPP) production of such ecosystems. In our paper, daytime Reco fluxes are compared with nighttime CO2 fluxes which were measured manually by the closed chamber technique on a wetland site in Poland. The CO2 fluxes measurements were performed between July 2008 and May 2009. Our study indicated that there are significant differences between modeled daytime and nighttime Reco fluxes and that these differences are higher when the nighttime fluxes are restricted only to nights with stable atmospheric conditions. The nighttime sums of cumulative Reco are much higher than the one estimated for daytime conditions, while there is nearly no difference between daytime and nighttime sums of cumulative Reco, when the nighttime fluxes are restricted only for nights with turbulent atmospheric conditions. Consequently, Reco models developed on the basis of nighttime data series can overestimate CO2 fluxes when they are used to estimate daytime respiration. In order to reduce uncertainties in estimation of daily Reco fluxes on the basis of the nighttime chamber measurements, the nighttime Reco models should be restriced only to the fluxes that were measured in turbulent atmospheric conditions. The biases in nighttime chamber measurements (especially when conducted in stable atmospheric conditions) as well as differences in estimated daytime and nighttime Reco fluxes can have a significant effect on the assessment of global carbon balances of terrestrial ecosystems.