0000000000365156
AUTHOR
Sanna M. Leppänen
Nitrogen fixation and methanotrophy in forest mosses along a N deposition gradient
Abstract Nitrogen deposition has decreased the plant-associated nitrogen (N 2 ) fixation when measured using the indirect acetylene reduction assay (ARA). However, nitrogen deposition can also lead to changes in the diversity of moss symbionts, e.g. affect methanotrophic N 2 fixation, which is not measured by ARA. To test this hypothesis we compared ARA with the direct stable isotope method ( 15 N 2 incorporation) and studied methanotrophy in two mosses, Hylocomium splendens and Pleurozium schreberi , collected from seven forest sites along a boreal latitudinal N deposition transect. We recognized that the two independent N 2 fixation measures gave corresponding results with the conversion …
Methanotrophy induces nitrogen fixation during peatland development
Significance In peatlands, the external sources of nitrogen are mainly atmospheric, but the atmospheric nitrogen deposition alone cannot explain the long-term annual nitrogen accumulation rates to these ecosystems. Because of methodological problems, methane-induced fixation of atmospheric dinitrogen gas has been previously overlooked as an additional nitrogen input mechanism. We found that the activity of methane-oxidizing bacteria provides not only carbon but also nitrogen to peat mosses and, thus, contributes to carbon and nitrogen accumulation in peatlands, which store approximately one-third of the global soil carbon pool. Our results imply that nitrogen fixation in wetlands may be str…
Methanotrophs are core members of the diazotroph community in decaying Norway spruce logs
Dead wood is initially a nitrogen (N) poor substrate, where the N content increases with decay, partly due to biological N2 fixation, but the drivers of the N accumulation are poorly known. We quantified the rate of N2 fixation in decaying Norway spruce logs of different decay stages and studied the potential regulators of the N2-fixation activity. The average rate for acetylene reduction in the decaying wood was 7.5 nmol ethylene g−1d−1, which corresponds to 52.9 μg N kg−1d−1. The number of nifH copies (g−1 dry matter) was higher at the later decay stages, but no correlation between the copy number and the in vitro N2 fixation rate was found. All recovered nifH sequences were assigned to t…