Effects of Rewetting on Soil Organic Carbon and Fe-bound Organic Carbon Contents of A Degraded Peatland:A Case Study of Baijinghe Peatland
As one of the significant carbon pool within terrestrial ecosystems,changes in soil carbon in peat-lands have considerable implications for the global carbon balance.Soil enzymes and iron are important sub-stances which affect the decomposition of soil organic matter.This article focuses on the Baijianghe peatland as the research subject,with soil samples collected from the natural area,drained,and water level restoration area at depths of 0-20 cm in April 2021.Soil physical and chemical properties,different forms of iron con-tents,soil enzyme activity,iron contents,Fe-bound soil organic carbon,and soil organic carbon were mea-sured.The aims of this study were to clarify the relative importance of'enzyme latch'and'iron gate'mecha-nisms in soil organic carbon cycling within peatlands and to provide a data foundation for carbon pool man-agement during the restoration of degraded peatlands.The results showed that after two years of rewetting,soil pH increased but soil total nitrogen content decreased.Soil Fe2+and pyrophosphate-extractable iron ox-ides(Fep)exhibited a trend where the restoration area surpassed the drained area.In contrast,the contents of soil Fe3+,oxalate-extractable iron oxides(Feo),and dithionite-citrate-bicarbonate-extractable iron oxides(Fed)demonstrated a trend of the drained area exceeding the restoration area.Soil hydrolytic activities of the 0-5 cm depth decreased but the oxidase activities increased after rewetting.However,the activities of soil enzymes in the 5-20 cm depth did not change uniformly.Changes in soil enzyme activities were mainly affected by soil total nitrogen and iron content.In general,soil organic carbon and Fe-bound soil organic carbon contents in the restoration area were higher than those in the drained area.After rewetting,soil pyrophosphate-extractable iron oxides content increased which was benefit for the increasing of Fe-bound soil organic carbon content.However,the'iron gate'mechanism was not the main cause of soil organic carbon increasing after rewetting.Soil iron regulated soil organic carbon mainly through affecting enzyme activities.The'enzyme latch'mecha-nism was found to play a crucial role in regulating soil organic carbon during the rewetting process of degrad-ed peatlands in spring.
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