Biological nitrogen fixation in peatlands: Comparison between acetylene reduction assay and 15N2 assimilation methods

Abstract

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Experimental warming alters the community composition, diversity, and N2 fixation activity of peat moss (Sphagnum fallax) microbiomes

“…Slight differences in diazotroph activity were observed between 15 N incorporation and ARA methods across the warming treatments. This is consistent with recent peatland studies (Saiz, Sgouridis, Drijfhout, & Ullah, ; Warren et al, ) and is expected as acetylene is known to inhibit diazotrophic methanotrophs (Warren et al, ). Thus, 15 N incorporation measurements are more appropriate for estimating N 2 fixation in peatland ecosystems (Saiz et al, ).…”

The Global Distribution of Biological Nitrogen Fixation in Terrestrial Natural Ecosystems

“…Where a measurement is given for the entire growth season, we include it as representative of the whole year. Values must be in comparable units of nitrogen. Values only given in C 2 H 4 (ethylene) or C 2 H 2 (acetylene) are therefore excluded because conversion between C 2 H 4 and N is variable (Ley & D'Antonio, ; Nohrstedt, ; Saiz et al, ). However, where the author has made the conversion, we accept their scientific judgement. The measurements must be representative and not anomalous.…”

“…Values must be in comparable units of nitrogen. Values only given in C 2 H 4 (ethylene) or C 2 H 2 (acetylene) are therefore excluded because conversion between C 2 H 4 and N is variable (Ley & D'Antonio, 1998;Nohrstedt, 1985;Saiz et al, 2019). However, where the author has made the conversion, we accept their scientific judgement.…”

“…The conversion factor of 3:1 C 2 H 4 :N 2 is commonly assumed (Hardy et al, ) and was used by Cleveland et al ()) to convert values not already reported in units of nitrogen. But this conversion factor varies considerably, with studies suggesting anything from 1.6:1 to 5.6:1 (Nohrstedt, ) and 0.001:1 to 5.363:1 reported for peatlands with variation over space, time, and species (Saiz et al, ). This disparity is the reason we do not convert C 2 H 4 or C 2 H 2 measurements to N. Since ARA method measurements makes up a significant proportion of the measurements available and many studies have site‐specific conversion factors or use more than one method for verification, we include them.…”

Active Methanotrophs in Suboxic Alpine Swamp Soils of the Qinghai–Tibetan Plateau

“…It is a powerful method to quantify diazotrophic activity in complex environments. Although numerous studies have employed acetylene reduction assay (ARA) to measure nitrogen fixation, this method can suppress nitrogenase leading to biases in measurements (Saiz et al, 2019). Likewise, inhibition of acetylene to methane monooxygenase can underestimate the nitrogen-fixing potential by microbial methane oxidizers (Flett et al, 1975;Prior and Dalton, 1985).…”