Sustainable carbon retention from water input to wetlands at two temporal scales

Wetlands retain carbon from flowing water through biomass accumulation and deposition processes. However, the contributions of accumulated carbon from water to carbon storage and cycling in wetland ecosystems remain unclear. Moreover, there are no comprehensive estimates of the stability and sustainability of wetland performance in retention of carbon from water on different time scales. We conducted a meta-analysis (2889 paired observations) to estimate the stability and sustainability of constructed wetlands in retention of carbon from input water on short and long time scales. This study showed that the efficiency of carbon retention from water in wetlands significantly increased on short time scales, whereas it remained stable on long time scales and among different seasons. The usage of grave, alum sludge and all types of plant had higher effect sizes on short-term wetland water carbon retention, but the long-term stability of water carbon retention was not affected by substrates or plant types. Variations in precipitation as well as air temperature affected the short-term water carbon retention in wetlands, but they did not affect long-term water carbon retention in wetlands. However, on long time scale, the stability of water carbon retention in wetlands was challenged by operation time, low water temperature and high hydraulic load rate, which posed a threat to the sustainability of wetland performance in water carbon retention. In summary, this study demonstrated the stability and sustainability of carbon retention from water and proved the contribution of accumulated carbon from water to the carbon pool in wetland ecosystems.