Cyanobacteria associations in temperate forest bryophytes revealed by δ15N analysis1

Abstract

Abstract Bryophytes have an important biogeochemical role in many forest ecosystems, where they regulate soil temperature and moisture and influence carbon and nitrogen (N) cycling. Associations between bryophytes and N2-fixing cyanobacteria have been reported in northern latitude forests and are shown to provide a substantial N input to these ecosystems, but whether the association extends into temperate forests remains largely unknown. We investigated the extent of bryophyte-cyanobacteria associations in common understory bryophytes in a temperate forest in New York using δ15N analyses and ultraviolet fluorescence microscopy. Of the seven taxa examined, three (Fissidens taxifolius, Marchantia polymorpha, and Thuidium delicatulum) were associated with cyanobacteria, with colonization observed in 15–85% of the leaves examined. The taxa with cyanobacterial associations exhibited δ15N values that were 3.9‰ higher compared with taxa that did not, and the δ15N signatures were close to the atmospheric N2 signa...