[Impact of Differences in Vegetation Cover on Soil Organic Carbon Composition and Stability in Caohai]

Soil organic carbon （SOC） stability and carbon sequestration potential can be affected by vegetation cover. The Caohai in Guizhou is a typical plateau freshwater wetland ecosystem at the same latitude as other regions worldwide. The study focused on the soils from Caohai and selected five types of vegetation cover, including forest land, cultivated land, grassland, reeds, and tidal flats. Soil samples were collected vertically at depths of 0-20, 20-40, and 40-60 cm, and the activity and stability of SOC were tested to explore the impact of different vegetation covers on the composition and stability of SOC, finally providing basic data for soil carbon sequestration and ecological protection in the Caohai. The results indicated that cover variability led to differences in SOC content on the vertical distribution scale （P<0.05）. Comparing SOC content in various covers with tidal flats （14.75 g·kg^-1） on a horizontal scale, reductions were observed in forests （19.32%）, reeds （15.05%）, cropland （12.47%）, and grassland （1.58%）. The proportions of stable and labile organic carbon （SAOC and LOC） accounted for 52.51% and 45.00% of the total SOC content, respectively. The ω（ROC） （g·kg^-1） values were 7.89 （forests）, 7.47 （tidal flats）, 6.67 （reeds）, 6.36 （cropland）, and 5.67 （grassland）, with N/P and TN being the main physicochemical factors influencing ROC （r≥0.72）. ROCI ranged from 0.16 to 0.34, with the highest in forest land and relatively lower values in cropland and grassland, mainly affected by N/P （P<0.01）, negatively correlated with BD （P<0.05）, and influenced by cover type （P<0.001） and soil depth （P<0.01）. Both cover type and soil depth interacted significantly with ROCI （P<0.01）. The research indicated that vegetation cover variability altered organic matter decomposition and accumulation, leading to a differential distribution of organic carbon components. Agricultural activities affected the stability and accumulation status of organic carbon, contributing to the higher levels of unstable carbon components SAOC and LOC and exhibiting significant potential for soil carbon sequestration enhancement. Moreover, it is recommended to implement scientific management practices to transition towards a more stable state, thereby enhancing regional ROCI levels and carbon sequestration potential.