シモノ　アヤコ   Shimono Ayako   下野　綾子    所属   東邦大学  理学部 生物学科    職種   准教授
論文種別	原著
言語種別	英語
査読の有無	査読あり
表題	Mangrove–diazotroph relationships at the root, tree, and forest scales—diazotrophic communities create high soil nitrogenase activities in Rhizophora stylosa rhizospheres
掲載誌名	正式名：Annals of Botany ISSNコード：0305-7364
掲載区分	国外
出版社	Oxford Academic
巻・号・頁	125(1),pp.131-144
著者・共著者	Inoue, T., Shimono, A., Akaji, Y., Baba, S., Takenaka, A., and Chan, H. T.
担当区分	2nd著者
発行年月	2020/01/02
概要	Background and Aims The tidal flats on which mangrove plants grow tend to have low soil nitrogen contents because nitrogen-containing litter is repeatedly washed offshore by ebb tides. Under such circumstances, it is unclear how mangrove plants acquire the nitrogen required to support their vigorous growth. In the present work, chemical and biological characteristics of diazotrophy around mangrove plant roots were surveyed under natural conditions to elucidate mangrove–diazotroph relationships. Methods Soil nitrogenase activity of a representative mangrove plant, Rhizophora stylosa, which has a broad geographical distribution, was measured using the acetylene reduction assay at forest, tree and prop root scales. In addition, diazotrophic community composition was compared between rhizosphere and bulk soil based on sequencing of nifH genes. Key Results Soil nitrogenase activity was high near prop roots, and this pattern was enhanced as soil live root content increased. At the forest scale, we observed high soil nitrogenase activity (acetylene-reducing activity) inside the forest. Rates decreased sharply from the forest to the tidal flat. The nifH operational taxonomic unit composition differed significantly among forest and tree rhizospheres and the bulk soil. Conclusions Our results suggest that the accumulation of diazotrophs around R. stylosa mangrove trees enhances the supply of biologically fixed nitrogen to the mangrove roots. This supply is especially important when the soil naturally contains little nitrogen. This nitrogen acquisition system may be a key process that explains the high productivity of mangrove ecosystems.