Nitrogen fixation in soils of Truelove Lowland, Devon Island, Northwest Territories

1975 ◽  
Vol 53 (14) ◽  
pp. 1387-1399 ◽  
Author(s):  
R. C. Stutz ◽  
L. C. Bliss
Keyword(s):  
Nitrogen Fixation ◽  
Vascular Plants ◽  
Beach Ridge ◽  
Nostoc Commune ◽  
Cushion Plants ◽  
Devon Island ◽  
Reduction Assay ◽  
Sedge Meadows ◽  
Incubation Temperatures ◽  
Biological Nitrogen

Biological nitrogen fixation was studied on Truelove Lowland, Devon Island, N. W. T., in three different habitats. Raised beach ridges, resulting from postglacial uplift, form well-defined xeric habitats, which are dominated by dwarf shrubs and cushion plants. Hummocky sedge meadows with associated mosses and forbs comprise the second intensively studied habitat. Waterlogged wet sedge meadows with moss were studied less intensively.Nitrogen fixation was estimated using acetylene-reduction assay. Incubation temperatures were moderated by burying the jars in soil pits (10 cm) on site.Available nitrogen was determined by microkjeldahl analysis of KCl soil extracts.Symbiotic nitrogen fixation by vascular plants is nil on Truelove Lowland. One lichen species, Peltigera aphthosa, reduced acetylene (5.1 μμmol∙mg−1∙h−1). Nostoc commune, a prominent blue-green alga on meadow soils, reduced acetylene at a rate 10 times that of P. aphthosa. An estimated 30 and 7 mg N∙m−2∙year−1 was fixed by bacteria and soil algae in beach ridge soil in 1971 and 1972 respectively, and 380 and 120 mg N∙m−2∙year−1 was fixed in meadow soils in the same years.

Nitrogen fixation and photosynthesis in high arctic forms of Nostoc commune

1994 ◽  
Vol 72 (7) ◽  
pp. 940-945 ◽  
Author(s):  
R. Lennihan ◽  
D. M. Chapin ◽  
L. G. Dickson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Terrestrial Ecosystems ◽  
Growing Season ◽  
High Arctic ◽  
Colony Morphology ◽  
Nostoc Commune ◽  
Devon Island ◽  
Low Levels ◽  
Temperature Optima

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies of N. commune found on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction in N. commune (2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arctic N. commune but lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1 PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpina and Gleotrichia sp.), N. commune had higher rates of nitrogen fixation. Key words: Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosynthesis.

Environmental regulation of nitrogen fixation in a high arctic lowland ecosystem

1991 ◽  
Vol 69 (12) ◽  
pp. 2744-2755 ◽  
Author(s):  
David M. Chapin ◽  
L. C. Bliss ◽  
L. J. Bledsoe
Keyword(s):  
Nitrogen Fixation ◽  
Soil Moisture ◽  
Environmental Regulation ◽  
Acetylene Reduction ◽  
High Arctic ◽  
Spatial And Temporal Variation ◽  
Phosphorus Fertilization ◽  
Nostoc Commune ◽  
Nitrogen And Phosphorus ◽  
Devon Island

This study examined spatial and temporal variation in cyanobacterial nitrogen fixation and the environmental regulation of this variation at Truelove Lowland, Devon Island, N.W.T. Acetylene reduction rates of soil–plant cores from a variety of plant communities were measured under uniform conditions of light and temperature during the 1987 and 1988 growing seasons. Concurrent measurements of soil moisture and extractable nitrogen and phosphorus were also made. Effects of temperature, moisture, and phosphorus were examined in manipulative experiments. Acetylene reduction rates were highest in brackish environments, intermediate in mesic to hydric terrestrial and in aquatic communities, and lowest on xeric beach ridges. Rates generally increased during early season, then decreased through mid to late season. Among the three parameters examined, rates were most highly correlated to soil moisture. The temperature optimum for fixation was near 20 °C. There was a strong, but reversable, depression in acetylene reduction in response to experimental desiccation, and weekly phosphorus fertilization had a strong positive effect on fixation rates. The highest fixation rates along the marine shoreline were associated with high phosphorus input from marine algae and greater biomass of cyanobacteria. Because of the overriding importance of moisture, changes in nitrogen and phosphorus levels accompanying ecosystem development do not appear to strongly control nitrogen fixation in terrestrial, nonbrackish sites in this polar desert oasis. Key words: nitrogen fixation, environmental regulation, Devon Island, High Arctic, Nostoc commune, cyanobacteria.

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