Stem CH4 emissions from the reclaimed forests: magnitude, drivers, and contribution

Background Trees in natural forests are a major contributor to atmospheric methane (CH 4 ), yet these emissions have never been investigated in reclaimed forests. Our study aimed to assess the magnitude, seasonality, drivers, and contributions of tree CH 4 emissions to ecosystem CH 4 flux in the reclaimed forests. We measured CH 4 emissions from different emission pathways, including the stems of trees ( Populus euramericana , Metasequoia glyptostroboides , and Camphora officinarum ), shoots of herbs ( Carex breviculmis and Carex dispalata ), and soils in the two reclaimed forests with reclamation periods of 12 and 5 years. We identified factors controlling seasonal tree CH 4 emissions and measured tree morphological variables (diameter at breast height, wood density, and lenticel density) to determine species differences in emissions. Results CH 4 emissions from trees in the 12-year-old reclaimed forest were significantly higher than those in the 5-year-old forest. Seasonal variations in tree CH 4 emissions were primarily driven by growth stage and soil parameters, including soil CH 4 flux, temperature, and moisture. Conclusion In the reclaimed forests, tree-mediated CH 4 emissions could be an important contributor to ecosystem CH 4 flux, with contributions varying by season. As these forests mature and become ecologically restored, they may significantly impact regional and global CH 4 emissions.