Carbon Sequestration and Soil Accretion in Coastal Wetland Communities of the Yellow River Delta and Liaohe Delta, China

Rates of accumulation of particulate organic carbon (POC) and particulate inorganic carbon (PIC) as well as soil accretion rates were determined in the Yellow River Delta (YRD) and Liaohe Delta (LHD) in northeastern China. Rates of carbon accumulation were dominated by PIC accumulation in the YRD and by POC accumulation in the LHD. Rates of POC accumulation at sites above mean sea level were similar in the two deltas, 141 ± 17 g C m−2 y−1, but were much higher, 381 ± 10 g C m−2 y−1, at sites in the LHD below mean sea level. High rates of PIC accumulation in the YRD, 916 ± 133 g C m−2 y−1, reflect the very high concentration of dissolved inorganic carbon in the Yellow River, which in turn reflects the erosion of carbonate-rich glacial dust and evaporates minerals in the Loess Plateau, the excess of evaporation over precipitation in the watershed, and the fact that much of the flow in the river is diverted to irrigate crops. In both river deltas, accumulation of PIC was positively correlated with accumulation of POC, although the sources of the PIC are allochthonous and the sources of the POC are primarily autochthonous. Rates of POC accumulation were closely correlated with the species of wetland plants in the deltas. Although the rates of PIC accumulation in the YRD are exceptional, anthropogenic effects, including climate change, are creating conditions that will likely enhance PIC accumulation in many other river deltas.