Jing Bai , Min Luo , Yang Yang , Shuyao Xiao , Zhifeng Zhai , Jiafang Huang
{"title":"Iron-bound carbon increases along a freshwater−oligohaline gradient in a subtropical tidal wetland","authors":"Jing Bai , Min Luo , Yang Yang , Shuyao Xiao , Zhifeng Zhai , Jiafang Huang","doi":"10.1016/j.soilbio.2020.108128","DOIUrl":null,"url":null,"abstract":"<div><p><span><span>Globally, a vast extent of tidal wetlands will be threatened by sea-level-rise-induced salinization<span>. Because ferric (hydro)oxides [Fe(III)] play a crucial role in soil organic carbon (SOC) preservation, understanding the responses of the Fe-bound C pool to increasing </span></span>salinity<span> could assist in accurate prediction of the changes in C stocks in the tidal wetland soils<span> facing imminent sea-level rise. In this study, we investigated pools of Fe-bound C and SOC<span>, C-degrading enzyme activity<span>, Fe species contents and Fe-cycling bacteria, and plant properties along a salinity gradient from freshwater (0.0 ± 0.1 ppt; part per thousand) to oligohaline (2.6 ± 0.6 ppt) in a subtropical tidal wetland. Overall, the belowground biomass and the content of root Fe(III) plaque (a proxy of root oxygen loss potential) rose with the increasing salinity. Along the salinity gradient, the abundance of </span></span></span></span></span><span><em>Gallionella</em></span> (Fe-oxidizing bacteria) increased, but the abundance of <span><em>Geobacter</em></span><span><span> (Fe-reducing bacteria) decreased. The Fe(II):Fe(III) ratios decreased as salinity increased, implying that more Fe(II) was oxidized and immobilized into Fe(III) closer to the sea. Fe sulfides contents also elevated close to sea. The co-existence of Fe(III) and Fe sulfides at the oligohaline sites implied a high spatial heterogeneity of Fe distribution. During the growing season, the SOC pool generally decreased with increasing salinity, probably due to a reduction in aboveground-C input and enhanced activity of the C-degrading enzyme. The Fe-bound C pool was positively affected by the amorphous Fe(III) content and negatively related to the activity of phenol </span>oxidase. The Fe-bound C pool generally rose along the salinity gradient, with the importance of Fe-bound C to SOC increasing from 18% to 29%. Altogether, our findings implied that when the imminent sea-level-rise-induced salinization occurs, the total soil C stock may generally decrease, but Fe-bound C will become increasingly important in protecting the rest of the C stocks in tidal wetland soils.</span></p></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"154 ","pages":"Article 108128"},"PeriodicalIF":9.8000,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.soilbio.2020.108128","citationCount":"23","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soil Biology & Biochemistry","FirstCategoryId":"97","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0038071720304247","RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"SOIL SCIENCE","Score":null,"Total":0}
引用次数: 23
Abstract
Globally, a vast extent of tidal wetlands will be threatened by sea-level-rise-induced salinization. Because ferric (hydro)oxides [Fe(III)] play a crucial role in soil organic carbon (SOC) preservation, understanding the responses of the Fe-bound C pool to increasing salinity could assist in accurate prediction of the changes in C stocks in the tidal wetland soils facing imminent sea-level rise. In this study, we investigated pools of Fe-bound C and SOC, C-degrading enzyme activity, Fe species contents and Fe-cycling bacteria, and plant properties along a salinity gradient from freshwater (0.0 ± 0.1 ppt; part per thousand) to oligohaline (2.6 ± 0.6 ppt) in a subtropical tidal wetland. Overall, the belowground biomass and the content of root Fe(III) plaque (a proxy of root oxygen loss potential) rose with the increasing salinity. Along the salinity gradient, the abundance of Gallionella (Fe-oxidizing bacteria) increased, but the abundance of Geobacter (Fe-reducing bacteria) decreased. The Fe(II):Fe(III) ratios decreased as salinity increased, implying that more Fe(II) was oxidized and immobilized into Fe(III) closer to the sea. Fe sulfides contents also elevated close to sea. The co-existence of Fe(III) and Fe sulfides at the oligohaline sites implied a high spatial heterogeneity of Fe distribution. During the growing season, the SOC pool generally decreased with increasing salinity, probably due to a reduction in aboveground-C input and enhanced activity of the C-degrading enzyme. The Fe-bound C pool was positively affected by the amorphous Fe(III) content and negatively related to the activity of phenol oxidase. The Fe-bound C pool generally rose along the salinity gradient, with the importance of Fe-bound C to SOC increasing from 18% to 29%. Altogether, our findings implied that when the imminent sea-level-rise-induced salinization occurs, the total soil C stock may generally decrease, but Fe-bound C will become increasingly important in protecting the rest of the C stocks in tidal wetland soils.
期刊介绍:
Soil Biology & Biochemistry publishes original research articles of international significance focusing on biological processes in soil and their applications to soil and environmental quality. Major topics include the ecology and biochemical processes of soil organisms, their effects on the environment, and interactions with plants. The journal also welcomes state-of-the-art reviews and discussions on contemporary research in soil biology and biochemistry.