Point bars retained particulate organic carbon within a meandering river corridor in Zoige Basin of the Tibetan Plateau

Abstract

Carbon retention within river corridors influences ecosystem processes of catchments and regulates regional to global carbon budgets. Previous studies lack focus of carbon retention associated with meandering river migration. To fill the gap, this study concentrated on particulate organic carbon (POC) retention by point bars that built via hydrogeomorphic processes within meandering river corridors. We selected a typical meandering river (White River) in Zoige Basin of the Tibetan Plateau to conduct field works in the growing seasons of 2016, 2018, and 2019. We found (i) concentration of POC retained within point bars was 0.17%-2.52%, three to five times significantly lower than on general areas of floodplain, and did not show downstream trends; (ii) POC was homogeneously distributed within individual point bars, whereas the positions pioneer plants invaded had significantly higher concentrations; (iii) the order for POC concentration within the river corridor was: positions of bars without plants (1.08%) < positions of bars with pioneer plants (2.96%) < general area of floodplain (5.65%); (iv) the frequency of pioneer plants invasion increased downstream by advantage of the widened channel. Hydrogeomorphic processes through building point bars exerted an intense influence in modifying the POC concentration within the meandering river corridor.