title: Effects of available P and N:P ratios on non-symbiotic dinitrogen fixation in tallgrass prairie soils.
abstract: Prescribed burning is a major control over element cycles in Tallgrass prairie (Eastern Kansas, USA). In this paper we report potential effects of fire on nonsymbiotic nitrogen fixation. Fire resulted in additions of available P in ash, which may stimulate nitrogen fixation by terrestrial cyanobacteria. Cyanobacterial nitrogenase activity and biomass responded positively to additions of ash or P in laboratory assays using soil. Further assays in soil showed that cyanobacteria responded to changes in available N:available P ratio (aN:P) across a range of concentrations. Nitrogen fixation rate could be related empirically to aN:P via a log-linear relationship. Extrapolation of laboratory results to the field yielded a maximal estimate of 21 kg N ha-1y-1. Results support arguments from the marine and terrestrial literature that P availability is central to regulation of ecosystem N budgets.
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 80523, Fort Collins, CO, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Eisele
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 80523, Fort Collins, CO, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Schimel
authors.affiliation: Department of Botany, Miami University, 45056, Oxford, OH, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Kapustka
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, 80523, Fort Collins, CO, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Parton
keywords: Acetylene reduction; Ash; Cyanobacteria; Fire