Rapid carbon accretion and organic matter pool stabilization in riverine floodplain soils

The importance of wetlands in the global C budget has been recognized in recent years, and the high biomass productivity of riverine floodplains is widely acknowledged. However, soil C dynamics in these ecosystems are still poorly understood and rarely quantified. In this study, we quantify organic C accretion and examine changes of organic matter pools across an age gradient of riverine floodplain soils under different land uses in a warm temperate climate. We find rapid C accumulation during the initial 100 years of soil formation, with rates exceeding 100 g m −2 a −1 . We show that floodplain land use strongly affects soil C sequestration and organic matter pool allocation and find that the distribution of different soil organic matter pools reaches a steady state within a few decades of soil development. Our results demonstrate that continually rejuvenated soils on riverine floodplains are strong C sinks but also show that intensive cultivation severely compromises their high C sequestration potential.