Mechanisms of Environmental Factors Influencing CO2, CH4, and N2O Emissions under Intermittent Irrigation in Coastal Rice Fields of Northern Zhejiang, China

Abstract

Environmental conditions significantly affect greenhouse gas (GHG) emissions from rice paddies. Using an open-path monitoring system, this study investigated methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions from intermittently irrigated coastal rice fields in northern Zhejiang, China. The results revealed synchronized trends in air, soil, and rice canopy temperatures, all peaking at the late tillering stage. Gross primary production (GPP) and net ecosystem production (NEP) showed similar dynamics, with cumulative values of 850.51 and 294.36 g C/m2, respectively. Both GPP and NEP showed linear positive correlations with photosynthetically active radiation (PAR) and a quadratic relationship with vapor pressure deficit (VPD). CH4 emissions peaked at tillering, with daily fluxes of 0.02-1.19 g/m2/d and a total of 27.05 g/m2. Positive linear correlations were observed between CH4 emissions and temperature as well as VPD, explaining 15.12-17.37% and 10.14% of CH4 variation, respectively. The average N2O flux was 2.5281 μg·m-2·h-1, with higher cumulative fluxes during the jointing and booting stages. These results clarify GHG emission characteristics in northern Zhejiang’s rice fields and support the development of mitigation strategies.