Variations and Drivers of Methane Fluxes from Double-Cropping Paddy Fields in Southern China at Diurnal, Seasonal and Inter-Seasonal Timescales

Abstract

Methane (CH4) is the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2), and paddy fields are among the largest sources of CH4 emissions. Owing to the scarcity of observational data, the characteristics and influencing factors of CH4 fluxes in paddy fields at different timescales need to be further investigated. Observations of CH4 fluxes via eddy covariance (EC) data were performed over four seasons in two paddy fields in Nanchang, Jiangxi Province, China. The pattern, magnitude and biophysical controls of CH4 emissions were explored by wavelet analysis and stepwise multiplicative modelling. The results revealed a distinct, single-peak diurnal pattern in CH4 fluxes during the vegetative stage in all four rice growing seasons and the reproductive stage of early rice. Large seasonal variations in daily CH4 emissions were observed in the two double-cropping paddy fields, and the soil temperature at a depth of 5 cm (Ts5) explained most of the seasonality of the CH4 fluxes. At the inter-seasonal scale, under local farms’ traditional field management method, reducing the amount and frequency of irrigation during the vegetative stage could decrease CH4 emissions in southern China. This study improves the understanding of CH4 emissions and helps in developing GHG management strategies for paddy fields.

The Linkage Between Methane Fluxes and Gross Primary Productivity at Diurnal and Seasonal Scales on a Rice Paddy Field in Eastern China

“…This diurnal pattern of GPP was similar to findings of a rice paddy in Yancheng (Ge et al., 2018), Philippines (Alberto et al., 2014), USA (Hatala et al., 2012) and India (Bhattacharyya et al., 2013). As reported by previous studies (Knox et al., 2016; L. Ma et al., 2021; Miyata et al., 2000), CH 4 fluxes at this study site reached diurnal peaks around 13:00–15:00. Our average seasonal peak of GPP was 16.86 g C m −2 day −1 , higher than the peak value of 12 g C m −2 day −1 in Philippine rice fields (Alberto et al., 2009, 2014), and lower than the value of 18.04–20.56 g C m −2 day −1 reported by C. Chen et al.…”

“…Nevertheless, the total CH 4 emission during the growing season was site dependent due to different environmental conditions, soil properties, rice varieties, and field management practices (Wang & Li, 2002). Mean daily CH 4 /GPP in growing seasons ranged from 3.5% to 6.4% at this rice paddy field (Table 1), consistent with the results of Ge et al (2018) and L. Ma et al (2021). However, it was significantly higher than the values (<3%) reported by other studies (Bao et al, 2022;Bhattacharyya et al, 2014;Li et al, 2021;Meijide et al, 2017;Miyata et al, 2005;Shim et al, 2016), which can be attributed to the differences in water management and crop fertilizer application.…”

Diurnal variation in methane emission from a rice paddy due to ebullition

“…Some previous reports proposed that a plant physiological process plays a role in shaping the diurnal pattern of CH 4 emission through greater root exudates (i.e., substrates for methanogenesis) associated with leaf photosynthesis in the daytime (Hatala et al, 2012;Knox et al, 2016;Ma et al, 2021).…”

Optimization Analysis of Pretreatment Device Structural Parameters for Low-Concentration CBM Utilization

“…When the monitoring results remain constant after 5000 iterations, the calculated results are considered to have converged. The numerical simulation of gas mixing unit is essential to solve 2 Geofluids the continuity equation, momentum equation, energy equation and component transport equation, and its expression is as follows: Continuity equation:…”

“…Coalbed methane (CBM) is homologous with coal, and its main component is methane [1]. Methane is the second largest greenhouse gas after carbon dioxide [2], and its warming effect and potential are higher than carbon dioxide, which has a significant impact on the global greenhouse effect [3]. In recent years, methane emission reduction has become the focus of many areas of research [4].…”