Soil Active Organic Carbon Components And Enzyme Activity Characteristics Across Typical Plant Communities In Coastal Wetlands

Soil active organic carbon is a sensitive indicator of changes in soil carbon pool,which can reflect the turnover process of soil carbon pool in time.Different active organic carbon components have different physical properties,respond differently to changes in the external environment,and their influencing factors also vary greatly.Coastal wetlands are located between the ocean and the land,subject to the dual action of the ocean and the land.In this study,soil samples at 0-10 cm(surface layer),10-30 cm(middle layer)and 30-60 cm(deep layer)depths of four typical plant communities were collected to explore the distribution characteristics and influencing factors of soil active organic carbon components in different soil layer in Yancheng coastal wetlands.The content of TOC,EOC,DOC and POC content were measured and the correlation between soil carbon components and soil factors and aboveground biomass were analyzed.Our research results are as follows:(1)Among different plant communities,Spartina alterniflora community had higher total organic carbon and active organic carbon content,the total content of Suaeda salsa community was the lowest,and there was relatively little difference between Scirpus triqueter community and Phragmites australis community.In different soil layers,the TOC content of Spartina alterniflora community was slightly higher in the deep layer,and the other communities showed a downward trend with increasing depth;there was no consistent change rule of EOC and DOC content on the vertical profile;the content of POC gradually decreased with increasing soil depth.(2)From the trend of the proportion of EOC to TOC,the evaluation results of the relative stability of soil organic carbon were Spartina alterniflora community > Scirpus triqueter community > Phragmites australis community > Suaeda salsa community.On the vertical section,the Spartina alterniflora community and Scirpus triqueter community showed that active organic carbon content was higher in surface soil layer,while the deep soil organic carbon pool was composed of more inactive organic carbon.Suaeda salsa community and Phragmites australis community had a higher proportion of active organic carbon in deep soil layer,and deep soil organic carbon pool is composed of more active organic carbon.(3)There are large differences in the influencing factors of the three types of soil active carbon components.TN and TP had a greater impact on the EOC content in surface layer,while DOC and POC content were more affected by the aboveground biomass and soil redox status;the content of soil DOC in the middle layer was more affected by soil nitrogen and phosphorus nutrients and water content,while POC was closely related to aboveground biomass and soil redox status;DOC in deep layer was significantly affected by p H,and EOC and POC had no significant factors.Our study shows that the effects of AGB and p H on the content of soil organic carbon components at the three soil layers are more significant,while the effect of soil redox status is more significant with the increase of soil depth,and the relative content of soil organic carbon components and its influencing factors vary greatly depending on the soil level and composition type.In order to explore the characteristics and influencing factors of soil enzyme activities in Yancheng coastal wetlands,soil invertase,phosphatase and invertase activities of typical plant communities were measured,and the correlation between soil enzyme activity and soil factors and aboveground biomass were analyzed.Our research results are as follows:(1)The activities of soil invertase and phosphatase in Spartina alterniflora community and Scirpus triqueter community were higher,and those in Phragmites australis community and Suaeda salsa community were relatively low.Soil catalase activity was highest in Scirpus triqueter community,and was lowest in Spartina alterniflora community,and the difference between Phragmites australis community and Suaeda salsa community was small.Among different soil layers,the activities of soil invertase and phosphatase showed a decreasing trend with the increase of soil depth,while the activity of catalase was lowest in the surface layer.(2)Soil invertase activity was mainly affected by AGB,soil TN and SWC;soil phosphatase was mainly affected by soil TN and RS;soil catalase activity was mainly affected by aboveground biomass,soil BD,EC and SWC.To sum up,the soil active organic carbon content and soil enzyme activity in Yancheng coastal wetlands vary greatly depending on the community type and soil layer.Our research results can provide a theoretical basis for the ecological restoration and function enhancement for Yancheng coastal wetlands.