Contrasting Effects of Short-Term Litter Removal on Soil Respiration in Native Phragmites Australis and Exotic Spartina Alterniflora Marshes

Salt marshes produce substantial amounts of plant litter, playing a vital role in the long-term accumulation of soil organic carbon. However, the influences of plant litter on soil respiration in salt marshes remain largely unclear, especially when global salt marshes are threatened by plant invasion. We conducted a field experiment to examine how litter removal impacts soil respiration through soil physicochemical properties (temperature, moisture, pH, salinity, inorganic nitrogen, organic carbon) and plant growth (height, density, aboveground biomass) in native Phragmites australis and exotic Spartina alterniflora salt marshes. The results indicated that litter removal had contrasting effects on soil respiration in the before and after S . alterniflora invasion. In P. australis marshes, litter removal decreased soil respiration by 38.3% due to increased soil salinity, while in S . alterniflora , it enhanced soil respiration by 25.9% through increased AGB. Although the litter removal can affect level of soil inorganic nitrogen, pH and organic carbon, these are not the main factors that alter soil respiration. The study highlights that plant litter plays a crucial role in driving Rs in salt marshes, and the processes change with plant invasion. In the future, to accurately predict the carbon cycle process of salt marshes, it is necessary to comprehensively consider the complex relationships among vegetation types, litter, and soil properties.