Nitrogen Mineralization, Nitrification, and Denitrification in a High Arctic Lowland Ecosystem, Devon Island, N.W.T., Canada

1996 ◽  
Vol 28 (1) ◽  
pp. 85 ◽  
Author(s):  
David M. Chapin
Keyword(s):  
Nitrogen Mineralization ◽  
High Arctic ◽  
Devon Island ◽  
Nitrification And Denitrification

A survey of mycorrhizal plants on Truelove Lowland, Devon Island, N.W.T., Canada

1990 ◽  
Vol 68 (9) ◽  
pp. 1848-1856 ◽  
Author(s):  
C. Bledsoe ◽  
P. Klein ◽  
L. C. Bliss
Keyword(s):  
Plant Species ◽  
High Arctic ◽  
Cenococcum Geophilum ◽  
Soil Extracts ◽  
Vaccinium Uliginosum ◽  
Devon Island ◽  
Ericoid Mycorrhizae ◽  
Arctic Regions ◽  
Arctic Soils ◽  
Mycorrhizal Associations

Although mycorrhizal associations are commonly found on roots of most plant species, little is known about the presence or absence of mycorrhizae in arctic regions. In the Canadian High Arctic, roots of 55 herbaceous and woody plant species were examined for mycorrhizae during the summers of 1987 and 1988 on Devon Island, N.W.T. Ectomycorrhizal associations were found on roots of Salix arctica, Dryas integrifolia, and Potentilla hyparctica; ericoid mycorrhizae formed on Cassiope tetragona and Vaccinium uliginosum. Ectomycorrhizal roots were often covered with black hyphae resembling the fungus Cenococcum geophilum; sclerotia characteristic of this fungus were found in soil extracts. Plants expected to have endomycorrhizal associations were apparently nonmycorrhizal in the traditional sense, since no arbuscules, vesicles, or pelotons were found on any roots during two field seasons. Although extensive fungal hyphae were often present on and within roots, these hyphae could not be conclusively identified as endomycorrhizal. Some dark, septate hyphae were present; their function, although unknown, may be beneficial to the host. In a series of greenhouse bioassays using arctic soils, no endomycorrhizal associations developed on test plants. Spores of vesicular–arbuscular fungi were not found in soil extracts. Thus in this survey, only ectomycorrhizal associations were observed, suggesting that the cold, dry winter and cold, wet summer climates in this area of the High Arctic severely limit formation of endomycorrhizae. Key words: roots, fungi, ectomycorrhizae, endomycorrhizae, arctic.

Taxonomic and ecologic observations of zoosporic fungi in soils of a high-arctic ecosystem

1976 ◽  
Vol 54 (5-6) ◽  
pp. 533-538 ◽  
Author(s):  
Tom Booth ◽  
Paul Barrett
Keyword(s):  
Species Diversity ◽  
Species Composition ◽  
Soil Acidity ◽  
High Arctic ◽  
Arctic Ecosystem ◽  
Devon Island ◽  
Zoosporic Fungi

Phylctochytrium arcticum Barr and Rhizophlyctis harderi Uebelmesser are reported as additional taxa in soils of Truelove Lowland (Devon Island, N.W.T.) and Nowakowskiella spp., Olpidium pendulum Zopf, Pythium irregularae Buisman. Pythium spp., Phlyctochytrium arcticum, and Rhizophydium sphaerotheca Zopf are readily detectable as active organisms in Lowland microhabitats. Species diversity is greatest in mesic and warm soils and species composition of water-logged soils is different than dry soils. Soil acidity effects on distribution are discussed and autecological considerations of Nowakowskiella elegans and R. sphaerotheca with respect to pH, percentage N, C, and P, milliequivalents Ca2+ and Mg2+, moisture, and temperature are presented.

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.

scholarly journals A new hesperornithiform (Aves) specimen from the Late Cretaceous Canadian High Arctic with comments on high-latitude hesperornithiform diet

2016 ◽  
Vol 53 (12) ◽  
pp. 1476-1483 ◽  
Author(s):  
Laura E. Wilson ◽  
Karen Chin ◽  
Stephen L. Cumbaa
Keyword(s):  
Late Cretaceous ◽  
High Latitude ◽  
Upper Cretaceous ◽  
Current Knowledge ◽  
High Arctic ◽  
Time Of Death ◽  
Canadian High Arctic ◽  
Size And Shape ◽  
Devon Island ◽  
Paleoecological Reconstructions

Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of Devon Island, Nunavut, Canada. This specimen (NUVF 286) is referred to cf. Hesperornis sp. based on size and shape of femora and teeth preserved with other skeletal elements. Previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death. This new cf. Hesperornis specimen includes the first teeth associated with a high-latitude hesperornithiform, allowing for comments on the trophic behavior of these birds. Paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high-latitude hesperornithiform birds may have had more varied diets than previously assumed.

The patterning of plant communities and edaphic factors along a high arctic coastline: implications for succession

1994 ◽  
Vol 72 (8) ◽  
pp. 1095-1107 ◽  
Author(s):  
L. C. Bliss ◽  
W. G. Gold
Keyword(s):  
Plant Communities ◽  
High Arctic ◽  
Organic Soils ◽  
Similar Species ◽  
Edaphic Factors ◽  
Beach Ridges ◽  
Cushion Plant ◽  
Devon Island ◽  
Isostatic Rebound ◽  
Biological Development

Isostatic rebound and the periodic development of ice-push beach ridges have created topography suitable for development of biologically rich polar oases along the northeast coast of Devon Island, Canada. Distinct patterning of both plant communities and edaphic factors from coastal shoreline areas inland indicate primary succession with a directional species replacement At Rocky Point (emergent < 2000 BP) biological development along the shore is initiated by marine algae that are invaded by cyanobacteria. These organic mats are colonized by Puccinellia on the shoreline of these brackish lagoons. Where the topography grades upslope, via concave areas, the toposequence from Puccinellia proceeds through Dupontia → Carex → Salix hummocks → cushion plant–lichen communities. In drier, convex areas Puccinellia proceeds through rosette-herb hummocks → cushion plant–lichen communities as a toposequence. Reduced levels of salinity and of nitrogen fixation upslope (from the shore) along with increased depth of organic soils and ability of soils to hold more soil water appear important in the conversion of Puccinellia- to Dupontia- to Carex-dominated meadows. This is the major chronosequence at Rocky Point and it is these Carex meadows that occupy most of the wetlands of Truelove Lowland. The Salix hummocks and cushion plant–lichen communities of all drier habitats resemble communities of similar species composition on the beach ridges of the lowland. Key words: arctic Canada, succession, plant communities, soil factors, polar oasis.

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