Exploring sub-daily to seasonal variations in methane exchange in a single-crop rice paddy in central Japan

摘要

Methane (СЩ) is an important greenhouse gas, accounting for about 20% of the total direct radiative forcing from long-lived greenhouse gases since pre-industrial times. Rice paddy fields are known as a major source of CH4 in the terrestrial atmosphere. Many studies have thus investigated the source strength and environmental controls on СЩ exchange in rice paddies using the chamber technique and pot experiments. Despite these efforts, there is still large uncertainty regarding the global СЩ emissions from rice paddies. It is important to understand the transport pathways from the anoxic soil where СЩ is produced to theatmosphere, as well as the environmental controls on the transport processes. We applied the eddy covariance technique to observe ecosystem-scale CH4 exchange in a rice paddy field in central Japan (Kanto Region) in both the growing and post-harvest seasons. Our objectives were: 1) to clarify the environmental controls on ecosystem-scale CH4 exchange to infer the main transport pathways for the different stages of cultivation, and 2) to quantify the total annual СШ exchange in the rice paddy field.