Identification of two genera of N2-fixing cyanobacteria growing on three feather moss species in boreal forests of Quebec, Canada

The recent discovery that N-2 fixation rates by the feather moss carpet of boreal Scandinavian forests increases with stand maturity has put into question the paradigm that N-2 fixation is negligible in mature boreal forest. The N-2 fixation was attributed to a previously unknown association between Nostoc sp., a N-2-fixing cyanobacteium and Pleurozium schreberi (Brid.) Mitt., a feather moss that is abundant worldwide in the boreal forest. Here we report for the first time that this association also exists in the Canadian boreal forest. We discovered, however, that Nostoc was found growing not only on Pleurozium but also on two other moss species (Hylocomnium splendens (Hedw.) Br. Eur. and Ptillium crista-castrensis (Hedw.) De Not.). In addition, the N-2-fixing cyanobacterium Stigonema sp. was observed on the three moss species mentioned above, indicating the existence of six different associations. At least one of the six associations was found at 9 of 13 sites that are representative of a large area of the Quebec boreal forest. These findings suggest possibilities for further research, aimed at measuring the unaccounted for N-2-fixing potential of the feather moss carpet in Canadian boreal forests.