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Permafrost peatland plays an important role in the global carbon (C) cycle, and dissolved organic carbon (DOC) is one of the most important components to C budgets in this system. Through the Chinese–United States EcoPartnership program, Dr Xianwei Wang, Li Sun, and Prof Changchun Song et al. from the Northeast Institute of Geography and Agroecology of Chinese Academy of Sciences and Prof Aixin Hou from the Louisiana State University observed dynamics of DOC concentrations and specific ultraviolet absorbance at 254 nm (SUVA254) obtained from soil porewater of permafrost peatlands for two growing seasons in the Great Hing'an Mountains, Northeast China. Soil porewater DOC concentrations varied greatly with depths during the growing season, ranging between 22.08 and 65.02 mg L−1. There was no significant relationship between DOC concentrations and SUVA254. DOC concentrations were higher in autumn and increased as the seasonal thaw depth increased. DOC concentrations of supra‐permafrost water at freeze–thaw boundary were also higher than those at the other soil depths. Temperature and thawing depth had been shown to affect DOC concentrations at different soil depths. Our finding suggests that warming and deepening of the active layer likely increase the DOC productions in the permafrost peatland, which may influence the C balance in these C‐enriched ecosystems. [ABSTRACT FROM AUTHOR]

• CH 4 and CO 2 fluxes from two wetlands in northeast China are presented. • Most variations of CH 4 were distributed at time scales of several days to some months. • Soil temperature and thaw depth imposed alternated influences on CH 4 at the peatland. • Soil temperature and plant productivity influenced CH 4 emissions at the marsh. • Both wetlands were carbon sinks while the marsh had a net positive radiative forcing. Quantifying net CO 2 exchange (NEE) and CH 4 emissions of northern wetlands and their responses to biophysical controls are central to understanding the role of wetlands in global climate change. This study presents two growing seasons of observations of CO 2 and CH 4 fluxes by eddy covariance technique from a permafrost peatland and an inundated marsh in northeast China. Wavelet analysis was used to explore the temporal multi-scale variations of NEE and CH 4 fluxes and their biophysical controls. NEE showed prominent variations at the diel and the seasonal scales. However, most CH 4 variance was distributed at time scales longer than one day. At the permafrost peatland wavelet analysis revealed strong spectral coherency and alternating coherence between soil temperature and CH 4 fluxes during the spring and summer seasons and between thaw depth and CH 4 fluxes in the late growing season, with the suggestion of an as yet unknown coherence at longer timescales than could be resolved with just growing season records. At the marsh, soil temperature and CH 4 flux showed strong spectral coherency throughout the growing seasons and gross ecosystem production (GEP) additionally imposed its influence on CH 4 mainly during the most active part of the growing season. The growing season average CH 4 emission from the peatland (0.7 g C CH 4 m−2) was quite small and was negligible compared to its growing season NEE (−74.2 g C CO 2). In contrast, the growing season CH 4 emission from the marsh (average 31.1 g C CH 4 m−2) was considerably higher and accounted for about 16.2 % of its NEE (−191.7 g C CO 2 m−2). Although the two wetlands were net carbon sinks during the growing seasons and the permafrost peatland had a negative radiative forcing (i.e., cooling effect), the high CH 4 emissions from the marsh resulted in a net positive radiative forcing (i.e., warming effect). To understand the function of northern wetlands in the global carbon cycle, continuous field observations of these greenhouse gases are vital. [ABSTRACT FROM AUTHOR]