Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster V98

N fixing activity in moss associated cyanobacteria in response to grazing and experimental warming in Tundra ecosystems

Ana J. Russi , Ólafur S. Andrésson, Ingibjörg S. Jónsdóttir

University of Iceland and University Centre in Svalbard

Kynnir / Presenter: Ana J. Russi

Tengiliður / Corresponding author: Ana J. Russi (ajr2@hi.is)

Nitrogen (N) fixing moss associated cyanobacterial communities (MAC) are considered important contributors to the N budget in northern regions. Environmental change, including warming, is expected to affect bryophyte productivity and biomass, which may in turn cause change in N fixation patterns. In this study, we assessed the response of MAC to experimental warming in sub-arctic alpine ecosystems at two ITEX sites in Iceland (i) a grazed (sheep) mesic dwarf birch heathland (450 m elevation) largely covered by mosses, and (ii) an ungrazed Racomitrium moss heath on postglacial lava (120 m elevation). N fixation activity was assessed by the acetylene reduction assay (ARA). Estimation of cyanobacterial relative abundance and diversity was carried out with microscopy (phase-contrast, fluorescence and confocal scanning) and with amplification and sequencing of nifH, rpoB, rbcLx and 16S genes. Preliminary results suggested that both grazing and simulated climate warming negatively affected N fixation rates, also that the significant decrease of N fixing activity may largely depend on MAC identity and community composition. Our findings may have substantial impact on the understanding of the N cycle response to global environmental change in the Tundra.