Abstract
Coastal wetlands are considered as a significant sink of global carbon due to their tremendous organic carbon storage. Coastal CO2 and CH4 flux rates play an important role in regulating atmospheric CO2 and CH4 concentrations. However, the relative contributions of vegetation, soil properties, and spatial structure on dry-season ecosystem carbon (C) rates (net ecosystem CO2 exchange, NEE; ecosystem respiration, ER; gross ecosystem productivity, GEP; and CH4) 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 CH4 source (0.27 μmol m-2 s-1), whereas the Suaeda heteroptera and Tamarix chinensis stands uptook CH4 (-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 CH4); 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 CH4. 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.
Highlights
Carbon dioxide (CO2) and methane (CH4) are key greenhouse gases (GHGs) that make substantial contributions to global warming [1]
The gross ecosystem productivity (GEP) of P. australis was much greater than that of T. chinensis, which resulted in the highest value of net ecosystem exchange (NEE) in P. australis (Fig 2A and 2C)
The present study showed that NEE had a significant relationship with dissolved organic carbon (DOC), plant coverage, plant biomass, total phosphorus (TP), available phosphorus (AP), NO3, microbial biomass carbon (MBC), and Ta; ecosystem respiration (ER) had a significant relationship with soil organic carbon (SOC), plant coverage, plant biomass, TP, and soil water content (SWC); and GEP was closely related with plant biomass, plant coverage, AP, and NO3
Summary
Carbon dioxide (CO2) and methane (CH4) are key greenhouse gases (GHGs) that make substantial contributions to global warming [1]. Numerous studies have estimated global wetland CO2 and CH4 fluxes, but with great uncertainties, mainly due to complicated environmental drivers [2,3,4]. Coastal wetlands can act as greenhouse gas sinks via C burial, sediment deposition, and plant biomass accumulation, and as greenhouse gas sources through the release of CO2 and CH4 produced by the decomposition of organic matter [8], so they are of vital importance in governing the atmospheric concentrations of CO2 and CH4 [9]. Due to the complicated interaction of environmental factors including vegetation and soil properties, how to disentangle the contributions of multiple drivers to CO2 and CH4 fluxes in estuary wetland remains unclear
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