Comparison of Closed Chamber and Eddy Covariance Methods to Improve the Understanding of Methane Fluxes from Rice Paddy Fields in Japan

Nongpat Chaichana,Kosuke Noborio,Tiwa Pakoktom,Shujiro Komiya,Sonoko Bellingrath-Kimura,Yoshiharu Fujii,Ottfried Dietrich

doi:10.3390/atmos9090356

Abstract

Greenhouse gas flux monitoring in ecosystems is mostly conducted by closed chamber and eddy covariance techniques. To determine the relevance of the two methods in rice paddy fields at different growing stages, closed chamber (CC) and eddy covariance (EC) methods were used to measure the methane (CH4) fluxes in a flooded rice paddy field. Intensive monitoring using the CC method was conducted at 30, 60 and 90 days after transplanting (DAT) and after harvest (AHV). An EC tower was installed at the centre of the experimental site to provide continuous measurements during the rice cropping season. The CC method resulted in CH4 flux averages that were 58%, 81%, 94% and 57% higher than those measured by the EC method at 30, 60 and 90 DAT and after harvest (AHV), respectively. A footprint analysis showed that the area covered by the EC method in this study included non-homogeneous land use types. The different strengths and weaknesses of the CC and EC methods can complement each other, and the use of both methods together leads to a better understanding of CH4 emissions from paddy fields.

Highlights

Rice paddy fields are important sources of the global greenhouse gas (GHG) emissions, especially methane (CH4 ) [1]
The average CH4 fluxes the closed chamber (CC) method were 58%, 81%, 94% and 57% higher than those of the eddy covariance (EC) method at 30 days after transplanting (DAT), 60 DAT, calculated from the respectively
Flux was mainly driven by Ta_Eco (β = 2.960) and Ts_10 cm (β = 2.536), followed by RH (β = 1.252). These results showed that CH4 flux was mainly driven by Ta_Eco (β = 2.960) and Ts_10 cm

Summary

Introduction

Rice paddy fields are important sources of the global greenhouse gas (GHG) emissions, especially methane (CH4 ) [1]. Atmospheric CH4 emitted from rice paddies accounts for 10 to 40% of total natural CH4 emissions. Irrigated rice areas account for 70 to 80% of the CH4 emissions from global rice production [2,3]. Methane emissions from paddy fields are a dynamic process resulting from production by methanogenic bacteria under anaerobic soils and consumption by CH4 -oxidizing bacteria in aerobic conditions [4,5]. High rates of CH4 fluxes are found in soils with high soil organic matter content [6]. Low CH4 fluxes appear when soil contains high concentrations of ammonium and nitrate [7]. High temperatures and the increase in soil temperature stimulate the activities of soil

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