Biological Nitrogen Influx in an Ohio Relict Prairie

Abstract

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Factors Influencing Nitrogen Fixation and Nitrogen Release in Biological Soil Crusts

“…NA in Microcoleus-Collema soil crusts drops rapidly below soil water potentials of -33 kPa, with a 50 % reduction by -100 kPa (Rychert et al 1978). NA rates at a given moisture content vary within and between species (DuBois and Kapustka 1983;Kershaw 1985). Jones (1977d) found Nostoc commune in subtropical soils had maximal NA rates at 22-126 % water content by weight, while Coxson and Kershaw (1983b) showed maximal NA rates at 500 % water content in Nostoc from a northern temperate grassland soil.…”

“…Most soil cyanobacteria and cyanolichens are capable of N fixation between -5 and 30°C. Optimum temperatures reported generally range from 20-30°C for crusts in the Arctic, Antarctica, Scotland, Canada, South Africa, and subalpine regions (Jones 1977b;Coxson and Kershaw 1983a;Davey and Marchant 1983;DuBois and Kapustka 1983;Fritz-Sheridan 1988;Lennihan et al 1994). However, studies of temperature optimum must be interpreted carefully.…”

“…After freezing, recovery of NA is dependent on conditions before and after the freezing event. Freezing has the ability to damage nitrogenase in Nostoc (DuBois and Kapustka 1983;Scherer et al 1984). Low temperatures can reduce photosynthetic rates and thus reduce available ATP and reductant pools, creating a lag time after freezing before N fixation is initiated (Kershaw 1985).…”

“…When Nostoc was frozen for 3 days and then thawed at different temperatures, recovery of NA to prefreeze levels was much faster at 25 and 30°C when compared to lower temperatures. Light exposure before freezing reduced recovery time, as well as protein synthesis inhibition, indicating the need for de novo nitrogenase production (DuBois and Kapustka 1983;Scherer et al 1984).…”

“…16; Dodds et al 1995;GarciaPichel and Belnap 1996). In many studies, Nostoc showed an increase in NA up to 100-150 μmol m -2 s -1 PPFD, after which maximal NA rates are maintained (Jones 1977b;DuBois and Kapustka 1983;Fritz-Sheridan 1988;Lennihan et al 1994). Other species, including Calothrix, Stigonema, and Scytonema, also reach maximal NA rates at lower PPFD levels, which are maintained at higher light as well (Griffiths and Gallon 1987;Fritz-Sheridan 1987).…”