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

Abstract

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.