Symbiotic moss-cyanobacteria associations as a novel source of biological N2-fixation in temperate grasslands

Aims. Terrestrial mosses contribute significantly to nitrogen budgets in boreal forests through symbiotic associations with N2-fixing cyanobacteria, but few studies have considered these interactions in temperate systems. We investigated how N2-fixation by moss-cyanobacterial associations contribute spatio-temporally to site-level N dynamics in a western North American prairie ecosystem.

Methods. We first tested for the presence of N2-fixing cyanobacteria on six moss species using epi-fluorescence light microscopy. We then used an acetylene reduction assay to estimate monthly N2-fixation rates in moss-cyanobacteria associations across three prairies located in the Puget Sound, Washington State, USA. We evaluated temperature and precipitation effects on N2-fixation activity. 

Results. We confirmed the presence of N2-fixing cyanobacteria on three moss species (Pleurozium schreberi (Brid.) Mitt., Racomitrium elongatum Frisvoll, Rhytidiadelphus triquetrus (Hedw) Warnst.) and found spe...