Effects Of Biochar And Wetland Litter On Mineralization Of Organic Carbon In Coastal Wetlands Of The Yellow River Delta

Nowadays, there have been several urgent environmental problems to be solved such as climate changes and global warming, therefore, people need to propose an effective countermeasure to face them. It is well-known that, the carbon cycle of wetland ecosystem plays an important role in the global carbon cycle. Wetland in the Yellow River Delta, which has widest areas in northern China, is a new coastal wetland. The typical problem in the Yellow River Delta is the saline-alkalined soils. The serious salinization goes against the growth of plants and soil carbon sequestration. Meanwhile, the fast decomposition rate of soil carbon leads to carbon loss. So seeking a new material that both can cope with the greenhouse effect and restore the Yellow River wetlands is the priority, and biochar (BC) makes it possible.Great interest in the use of BC to improve soil quality has rapidly increased. Application of BC as a soil amendment in coastal wetlands in the Yellow River Delta may affect soil organic carbon (SOC) mineralization, which has significant contribution on the carbon (C) sequestration in wetlands. Thus, an incubation experiment over 150 days was conducted to investigate the effects of adding BC at rates of 0%(CK),0.1%(0.1%BC),1%(1%BC) and 3%(3%BC) on SOC mineralization and the corresponding mechanismsResults showed that:Total CO2 cumulative emissions increased due to labile C in the BC with increasing BC adding rates. About 60% of total CO2 cumulative emissions were mineralized by 15 days. The rates then rapidly decreased. As incubation time extended (>50 days), the rates were nearly to 0.Dissolved inorganic carbon (DIC) tended to increase in the early days, and then decrease. Increasing BC addition rates lead to much lower DIC contents in soils in later period. It indicated there may exist the process transferring from SOC to the soil inorganic carbon (SIC) in the salinized wetland soils. BC accelerated this process. It was confirmed by scanning electron microscope (SEM).By calculation, under 1% and 3% BC application, the actual maximum of mineralization was much lower than the theoretical. The actual maximum of SOC cumulative mineralization in 1%BC treatment was very similar to that in 3%BC. It suggested that a significant C sequestration effect occurred in salinized wetland soils with 350℃ peanut BC application. The correlation analysis showed dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were main factors influencing mineralization. In the early period, amounts of CO2 cumulative emissions and cumulative mineralization increased due to the labile C in BC. Due to the sorption of BC and stabilizing SOC through organo-mineral interactions, soil C sequestration happened as labile organic carbon depleted.To compare different effects of BC with reed application on SOC mineralization, an incubation experiment over 150 days was conducted including CK (control), 3%BC,3%reed treatments.Results showed that:Under same application rates, total CO2 cumulative emissions were always higher than the treatment with BC. Total CO2 cumulative emissions were 231.23 mg C/kg and 38.28 mg C/kg in 3%BC and 3%reed treatments respectively. As incubation time extended (>50 days), the rates of the CK,3%BC treatments were nearly to 0, but the rate of 3%reed treatment was 0.34 mg C/kg. Thus, exogenous organic matter in 3%reed treatment was much more easily to decompose than that in 3%BC treatment under same applicate rates.By the microbial quotient analysis, the values of microbial quotient in 3%reed treatment were always higher than that in 3%BC treatment. What’s more, the values of microbial quotient in 3%reed treatment were higher than that in CK treatment by 50 days. It suggested that reed application increased the utilization efficiency of microorganisms for soil organic carbon. That is to say, reed application may stimulate the utilization of carbon by microorganisms and facilitate the process of soil organic carbon mineralization. By comparison, the reed had much more degradable components, which release to the atmosphere in form of CO2 after degradation, than the BC under same application rates. The BC produced from the ordinary biomass by pyrolysis, makes contribution to the carbon sequestration.