The Accumulation Of Phenolic Compounds During Peatland Degradation And Its Effects On Dissolved Organic Carbon

Peatland is rich in carbon reserves and has important value in biodiversity conservation,climate and hydrological regulation,agriculture and animal husbandry,etc.However,under the influence of human and natural factors,the degradation of peatland is increasingly serious.As an important component of organic carbon in peatland,phenolic compounds have strong antioxidant activity and biotoxicity,which can inhibit the decomposition of organic carbon and slow down the carbon loss in peatland.However,the response of phenolic compounds to peatland degradation is widely controversial,and the potential relationship between phenolic soil carbon and vegetation communities during peatland degradation has not been explored.To solve this problem,typical sequence of retrograde succession peatlands(S1 peat swamp,S2 swamp meadow and S3 alpine meadow)in Riganqiao area of Zoige Plateau,China were selected as the research object in this experiment.In this study,vegetation succession,phenolic compounds and soil carbon content accumulation during peatland degradation were studied by field investigation and liquid chromatography analysis.And explore the potential relationship Among vegetation,phenols and soil carbon.The main conclusions are as follows:1.Regularity of vegetation change during peatland degradationWith the degradation of peatland,the aboveground vegetation community structure tends to be complex,and the most intuitive is the significant increase in vegetation biomass and coverage(P<0.05).Vegetation diversity and richness increased significantly with the degradation of peatland(P<0.05).The plant species gradually evolved from aquatic plants to terrestrial plants.Aboveground biomass increased significantly with the degradation of peatland(from 153 g/m~2to 649 g/m~2)(P<0.05),while the aboveground biomass and the height of vegetation community increased first and then decreased,and both reached the highest values in S2 swamp meadow.The total phenols of plants increased significantly with degradation(P<0.05),which may lead to more phenolic compounds being imported into the soil system.In addition,the degradation of peatland accelerated the succession of vegetation communities,increased underground biomass and abundance of gramineae and cyperaceae plants,and more decomposable plant residues entered the soil system,which may increase the carbon input level of vegetation communities.2.Changes of soil phenolic compounds during peatland degradationThe content of water-soluble phenols increased with the degradation of peatland,while the content of total phenols increased first and then decreased.In peat swamp and swamp meadows,the contents of water-soluble phenols were uniformly distributed in 0-10 cm,10-20 cm and 20-30 cm soil layers.In alpine meadows,the contents of water-soluble phenols were mainly distributed in the 10-20cm soil layer(161.795 mg/kg),and the contents in the 0-10cm soil layer were the least distributed(76.623 mg/kg).There was no significant difference in the distribution of total phenol content in each degradation stage.During the degradation of peatland(swamp meadow to alpine meadow),the water level drops,forming an oxygen-rich environment,and monophenols are converted to polyphenols under the action of enzymes The content of polyphenol gallic acid(GA)was significantly increased(P<0.05),the content of monophenol was significantly decreased(P<0.05),and the content of diphenol was not significantly decreased.Polyphenols have more phenolic hydroxyl groups,and their antioxidant activity and biotoxicity are stronger.Therefore,the increase of polyphenols may be beneficial to inhibit carbon decomposition in peatland.3.Peatland degradation affects phenolic compounds and carbon accumulation by changing vegetationDuring the transition from peat swamp to alpine meadow,the content of DOC and total carbon in the soil increased significantly(P<0.05).Regression analysis showed that DOC and total carbon were positively correlated with vegetation biomass and total phenols.The results indicated that there was a close relationship between vegetation and soil carbon in peatland,and the biomass of vegetation and the total phenol content of plant body were the possible reasons for regulating soil carbon content.Phenolic compounds had a significant positive effect on DOC accumulation.Monophenols,polyphenols and water-soluble phenols all had significant positive effects on DOC content.Phenolic compounds can effectively inhibit the decomposition of unstable carbon such as DOC,which plays an important role in the carbon stabilization of peatland.In conclusion,vegetation,phenolic compounds and carbon are closely related to each other.Therefore,future research and exploration on peatland should take the whole peatland system as the guide,and study the plant-soil system as a whole to clarify its internal relationship and mechanism.It has laid a solid foundation for the study of phenolic compounds in peatland,which is of great significance in the protection and restoration of peatland.