Plant biomass and soil organic carbon are main factors influencing dry-season ecosystem carbon rates in the coastal zone of the Yellow River Delta

Coastal wetlands are considered as a significant sink of global carbon due to their tremendous organic carbon storage. Coastal CO(2) and CH(4) flux rates play an important role in regulating atmospheric CO(2) and CH(4) concentrations. However, the relative contributions of vegetation, soil properties, and spatial structure on dry-season ecosystem carbon (C) rates (net ecosystem CO(2) exchange, NEE; ecosystem respiration, ER; gross ecosystem productivity, GEP; and CH(4)) remain unclear at a regional scale. Here, we compared dry-season ecosystem C rates, plant, and soil properties across three vegetation types from 13 locations at a regional scale in the Yellow River Delta (YRD). The results showed that the Phragmites australis stand had the greatest NEE (-1365.4 μmol m(-2) s(-1)), ER (660.2 μmol m(-2) s(-1)), GEP (-2025.5 μmol m(-2) s(-1)) and acted as a CH(4) source (0.27 μmol m(-2) s(-1)), whereas the Suaeda heteroptera and Tamarix chinensis stands uptook CH(4) (-0.02 to -0.12 μmol m(-2) s(-1)). Stepwise multiple regression analysis demonstrated that plant biomass was the main factor explaining all of the investigated carbon rates (GEP, ER, NEE, and CH(4)); while soil organic carbon was shown to be the most important for explaining the variability in the processes of carbon release to the atmosphere, i.e., ER and CH(4). Variation partitioning results showed that vegetation and soil properties played equally important roles in shaping the pattern of C rates in the YRD. These results provide a better understanding of the link between ecosystem C rates and environmental drivers, and provide a framework to predict regional-scale ecosystem C fluxes under future climate change.