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

Background Trees in natural forests are a major contributor to atmospheric methane (CH4), yet these emissions have never been investigated in reclaimed forests. Our study aimed to assess the magnitude, seasonality, drivers, and contributions of tree CH4 emissions to ecosystem CH4 flux in the reclaimed forests. We measured CH4 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 CH4 emissions and measured tree morphological variables (diameter at breast height, wood density, and lenticel density) to determine species differences in emissions. Results CH4 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 CH4 emissions were primarily driven by growth stage and soil parameters, including soil CH4 flux, temperature, and moisture. Conclusion In the reclaimed forests, tree-mediated CH4 emissions could be an important contributor to ecosystem CH4 flux, with contributions varying by season. As these forests mature and become ecologically restored, they may significantly impact regional and global CH4 emissions.