Dissolved organic matter movements from forests influence downstream soil CO2 flux during thawing

Abstract

Soil CO2 flux is critical for atmospheric carbon emissions and is highly influenced by soil respiration. Dissolved organic matter (DOM) from upland forests can transport to downstream wetlands and then influence soil respiration during thawing. Current studies have mainly focused on a uniform forest or wetland, whereas the soil CO2 flux changing characteristics affected by watershed DOM movements within the forest wetland catchment during thawing are rarely understood. In this study, the in situ measurement, field sampling, and multiple analysis methods were adopted. First, the soil CO2 flux and soil respiration rates were acquired by eddy covariance tower and portable greenhouse analyzer, respectively. The higher soil CO2 flux occurred during thawing might be partly attributed to the bursts of stored CO2. Then, the relationship between dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in water samples, and soil CO2 flux was analyzed by linear regression analysis. DOM from forests can be transported to downstream wetlands via surface runoff, and then promotes soil CO2 flux during thawing. Finally, the soil microbial abundances near the in situ measured sites of forests and wetlands were also compared with the corresponding soil respiration rates. LMWs contains in DOM inputs may influence soil respiration rates by altering soil microbial abundance. Overall, watershed DOM movement from forests can influence downstream soil CO2 flux during thawing in which microbes might exert effects via altering soil respiration rates.