Methane (CH₄) produced in rice-paddy soil is transported to the atmosphere either via the rice plants or by bubbling events (ebullition); however, little is known about the frequency and intensity of bubbling CH₄ emissions and the factors that affect them. We developed a method to quantify ebullition using high-time-resolution (~1 Hz) CH₄ concentration data obtained by closed-chamber measurements. Field measurements were conducted in a Japanese rice paddy at different rice growth stages: panicle formation (PF), booting (BT), and heading (HD). A dataset of 132 chamber measurements was used to develop and evaluate the method. A scripting file written in R programing language was used to automatically determine CH₄ emissions via the two pathways. Plant-mediated CH₄ emission intensity was constant during chamber deployment and was reflected as a steady linear increase in chamber [CH₄] with time or as a constant baseline in a flux time series. We found that the plant-mediated emission could be determined as the peak with the lowest flux intensity in the flux frequency distribution even if bubbling events occurred during the chamber deployment. The field measurement results in combination with established data processing protocols showed that at PF, ebullition contributed only 4% of the total emission, whereas it accounted for 32% and 60% of the total emission at BT and HD, respectively. In contrast, the plant-mediated flux variation among growth stages was smaller. Both ebullition and plant-mediated emissions correlated significantly with air temperature at HD, but the magnitude of the dependency was much higher for ebullition than for rice-mediated emission. These results demonstrate that ebullition occurs more frequently than has previously been thought, and the different transport pathways show varying degrees of dependency on plant phenological and environmental factors, thus underscoring the need to separately determine CH₄ emissions via each transport pathway.

中文翻译：

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使用密室测量期间获得的高时间分辨率浓度数据量化稻田中甲烷的鼓泡排放（沸腾）

稻田土壤中产生的甲烷（CH ₄）通过水稻或冒泡事件（沸腾）被输送到大气中；然而，人们对冒泡 CH ₄排放的频率和强度以及影响它们的因素知之甚少。我们开发了一种使用高时间分辨率 (~1 Hz) CH ₄浓度数据来量化沸腾的方法，该数据是通过密闭室测量获得的。田间测量在日本稻田的不同水稻生长阶段进行：穗形成 (PF)、孕穗 (BT) 和抽穗 (HD)。使用 132 个腔室测量数据集来开发和评估该方法。使用 R 编程语言编写的脚本文件自动确定 CH ₄两种途径的排放。植物介导的 CH ₄排放强度在腔室部署期间是恒定的，并反映为腔室 [CH ₄] 随着时间或作为通量时间序列中的恒定基线。我们发现，即使在腔室部署期间发生鼓泡事件，植物介导的排放也可以确定为通量频率分布中通量强度最低的峰值。现场测量结果结合已建立的数据处理协议表明，在 PF 处，沸腾仅占总排放量的 4%，而在 BT 和 HD 处分别占总排放量的 32% 和 60%。相比之下，生长阶段之间植物介导的通量变化较小。沸腾和植物介导的排放均与 HD 的气温显着相关，但沸腾的依赖性程度远高于水稻介导的排放。₄每个运输途径的排放量。