Effects Of Aboveground And Belowground Litter Input On Soil Respiration And Its Components In A Salt Marsh Wetland

Salt marsh wetlands play a critical role in terrestrial ecosystem carbon sinks due to its higher carbon accumulation rate.Soil respiration is an important flux to release carbon into the atmosphere,which has an important impact on the stability of soil carbon pool in salt marsh wetlands.The high productivity of salt marsh vegetation makes the aboveground and belowground litter become important in affecting soil respiration.However,current understanding for the effects of aboveground and belowground litter input on soil respiration and its components in salt marsh wetlands remains unclear.In this study,we established a brackish marsh mesocosms by adding aboveground litter and belowground litter of Spartina alterniflora to soil with and without plants to probe the regulation mechanism of litter input on soil respiration and its components.We measured soil respiration rate,plant biomass and soil microbial community structure in four treatments?control,add aboveground litter,add belowground litter,add aboveground and belowground litter?.The main results were as follows:?1?To explore the effects of aboveground and belowground litter inputs on soil respiration and its components in the salt marsh wetland,we continuously monitored soil temperature and soil respiration rate of each treatment.We found that the annual soil respiration and its components increased significantly after litter inputs,and the increase in soil heterotrophic respiration was significantly higher than that in soil autotrophic respiration.However,there was no significant difference among different types of litter.The temperature sensitivity(Q₁₀)and basal respiration(R₁₀)of soil respiration and its components were also unaffected by aboveground and belowground litter input,but with seasonal dynamics.The Q₁₀ in summer was higher than that in spring and visa versa for R₁₀,which were probably caused by seasonal changes in enzyme activities in plants and microorganisms.?2?The effects of aboveground and belowground litter on plant and soil microorganisms was studied by measuring plant biomass,carbon and nitrogen contents of plant leaves and stems,and soil microbial community structure.The results showed that litter input increased plant biomass,carbon and nitrogen contents of leaves and stems,and total soil microbial biomass.The effect of belowground litter on total soil microbial biomass was significantly higher than that of aboveground litter.Soil autotrophic and heterotrophic respiration were positively correlated with plant biomass and soil microbial biomass,which was regulated by plants and soil microorganisms respectively.Plants could enhance soil autotrophic respiration by absorbing nutrients from litter,and increasing root biomass and rhizosphere microbial activity,while soil microorganisms could improve their own activity and priming effect by decomposing litter.In conclusion,our study found that litter inputs affected soil respiration and its components in salt marsh wetlands by changing plant growth and soil microbial activity,highlighted the importance of litter to soil carbon emissions in salt marsh wetlands.Our results further deepen the understanding of the process and mechanism of soil carbon emissions in salt marsh wetlands,and provide data and theorecial basis for global models to accurately predict soil carbon release in salt marsh wetlands.