[Effects of Salt-tolerant Rice Cultivation on Organic Carbon Pool and Carbon Conversion Enzyme Activities in Coastal Saline Soil].

Cultivating salt-tolerant rice （STR） is an effective approach to ameliorating coastal saline soils （CSL）. In this study， the CSL without STR cultivation served as the control （CK）， while soils with different rice cultivation years （1-5 years） were the research objects. The one-way analysis of variance， redundancy analysis， Monte Carlo permutation test， Mantel test， and structural equation modeling were applied to investigate the changes and internal connections of soil organic carbon components， carbon pool quality， and carbon-converting enzyme activity under STR cultivation in CSL. The results showed that： ① Soil organic carbon content continued to rise after 2 a of STR cultivation， and the contents of microbial biomass carbon and easily oxidized organic carbon reached their peak values at 2 a and 4 a of cultivation， respectively. No significant difference in particulate organic carbon content in surface soil was found among different cultivation years， whereas its content in subsurface soil peaked at 5 years of cultivation. The contents of dissolved organic carbon in the surface and subsurface soil reached the highest values at 2 a and 4 a of cultivation， respectively. ② There was no significant difference in soil carbon pool activity among different cultivation years. Similarly， no significant difference in the carbon pool activity index of surface soil existed among different cultivation years， but the carbon pool activity index of subsurface soil reached the highest value at 4 years of cultivation， which was 84.4% higher than that of CK. Moreover， the carbon pool index was significantly higher than that of CK after 2 a of STR cultivation， and the carbon pool management index of surface and subsurface soil reached the highest values at 2 a and 4a of cultivation， respectively. ③ The activities of sucrase and amylase in the surface soil reached the highest values at 2 a of cultivation， which were 341.2% and 111.5% higher than those of CK， respectively， and there was no significant difference in the activities of sucrase and amylase in the subsurface soil among different cultivation years. The activities of soil β-glucosidase and polyphenol oxidase reached the highest and lowest values at 4a of cultivation， respectively， and the differences between them and CK were significant. ④ The activities of soil β-glucosidase and polyphenol oxidase were the key environmental factors affecting organic carbon components and carbon pool quality. The cultivation of STR improved the content of soil nutrients and available nutrients and stimulated the activities of hydrolytic and oxidative enzymes， thereby affecting the components of soil organic carbon and improving the soil carbon pool quality. In addition， the enhancement of the oxidative enzyme activity also weakened the quality of the soil carbon pool. This study is expected to provide a scientific basis for understanding the mechanism of soil organic carbon sequestration and the management of CSL under the cultivation of STR.