Moss-cyanobacteria associations as a novel source of biological N 2 -fixation in temperate grasslands
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Moss-cyanobacteria associations as a novel source of biological N2-fixation in temperate grasslands Lalita M. Calabria & Kate S. Petersen & Amanda Bidwell & Sarah T. Hamman
Received: 27 September 2019 / Accepted: 24 August 2020 # Springer Nature Switzerland AG 2020
Abstract Aims We investigated N 2 -fixation by mosscyanobacterial associations in a North American prairie ecosystem, identifying cyanobacteria associated with moss species, and evaluating spatio-temporal dynamics in N2-fixation rates. Methods We confirmed the presence and abundance of N 2 -fixing cyanobacteria on three moss species (Pleurozium schreberi (Brid.) Mitt., Racomitrium elongatum Frisvoll, Rhytidiadelphus triquetrus (Hedw) Warnst.) using epi-fluorescence light microscopy. To estimate monthly N2-fixation rates on mosses from three sites, we conducted laboratory-based acetylene reduction assays with constant incubation temperatures and natural daylight. We evaluated the relationship between
daylength and N2-fixation, and daylength and weather variables. Results N2-fixation rates varied by species, site, and month. R. elongatum exhibited the highest rates and P. schreberi had the lowest. Rates for R. elongatum and R. triquetrus were positively correlated with daylength, with peaks occurring at 13–14 h daylight, suggesting spring and fall conditions support N2-fixation in this system. Annual median N2-fixation for R. elongatum and R. triquetrus ranged from 0.008– 0.124 kg N ha−1 yr−1 based on cover of 11–100%. Conclusions Our results highlight a previously undescribed source of biological N2-fixation in temperate grasslands. Changes in the distribution or activity of N2-fixing moss-cyanobacterial associations due to management practices and climate change could impact future stand-level nitrogen dynamics.
Responsible Editor: Jeff R. Powell Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11104-020-04695-x) contains supplementary material, which is available to authorized users. L. M. Calabria (*) : K. S. Petersen The Evergreen State College, 2700 Evergreen Parkway NW, Lab 1, Olympia, WA 98505, USA e-mail: [email protected] A. Bidwell School of Environmental and Forest Sciences, The University of Washington, 1410 NE Campus Parkway, Seattle, WA 98195, USA S. T. Hamman The Center for Natural Lands Management, 120 Union Ave SE #215, Olympia, WA 98501, USA
Keywords Bryophytes . Cyanobacteria . Grasslands . Mosses . Nitrogen fixation . Prairies
Introduction Ground-dwelling bryophytes (mosses, liverworts, and hornworts) significantly influence global carbon (C) and nitrogen (N) cycles through contributions to aboveground biomass and associations with N 2 -fixing cyanobacteria (Cornelissen et al. 2007; Elbert et al. 2012). In boreal forest and arctic ecosystems, N2-fixation by moss-cyanobacteria associations is an important source of bioavailable N, where they contribute greater
Plant Soil
than 2 kg N ha−1 yr−1 (DeLuca et al. 2002; Rousk and Michelsen 2017). The association is th
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