Xudong Zhu*, Jingke Chen, Lichun Li, Mingjie Li, Tingting Li, Zhangcai Qin, Fan Wang, Xiaosong Zhao

Geophysical Research Letters

https://doi.org/10.1029/2023GL107235

Published: 04 June 2024

Abstract

The climate benefit of blue carbon sequestered by mangrove forests can be partially offset by CH4 emission, but this offset is rarely assessed using multi-year high-frequency measurements. Here, four-year eddy covariance measurements were used to examine temporal patterns of CH4 flux and its blue carbon offset (i.e., reduced climate benefit) in a subtropical estuarine mangrove in China. We found both diel and seasonal CH4 fluxes were mainly driven by soil temperature and tidal activities, showing greater nighttime emission. On average, one-tenth of CO2 uptake was offset by CH4 emission using the sustained-flux global warming potential metric at a 20-year time horizon, while this offset could vary over an order of magnitude due to asynchronous fluxes of CH4 and CO2 across diel and seasonal cycles. These results highlight the significant contribution of nighttime emission to mangrove CH4 budget and the importance of asynchronous flux variations in assessing mangrove's climate benefit.