In the Queen Elizabeth Islands, regional distributions of vegetation and many summer climate patterns show similar, distinctive S-shaped patterns, a response to the interaction between regional topography and persistent northwesterly flow from the central Arctic Ocean. The cool and cloudy central polar pack ice climate bulges almost unimpeded into the low-lying islands of the northwest and north-central sector. This region has the least vascular plant diversity and is dominated almost entirely by herbaceous species. The mountains of Axel Heiberg and Ellesmere islands create a barrier that effectively shelters an intermontane region from both the central Arctic Ocean climate and travelling cyclonic systems. In this large intermontane zone regional minimums of cloud cover and maximums of temperatures and melt season duration are found. This area contains the most dense and diverse vascular plant assemblages. Woody species and sedges dominate, and many species with more southerly limits occur as disjuncts. The plateaus and highlands in the southern islands modify the central Arctic Ocean climate sufficiently to produce an intermediate climate. Woody species and sedges also dominate this area; however, the density and diversity are less than that of the intermontane area. Several phytogeographic limits occur in the Queen Elizabeth Islands, including the northern limits of woody plants and sedges, and the northern limits of the dominance of woody plants and sedges. These regional boundaries roughly coincide with regional mean July isotherms of 3 and 4°C respectively.
Recent studies at Hot Weather Creek, Ellesmere Island document the climate and vegetation of a major part of the intermontane zone of Ellesmere Island. Summer temperatures in this region are much higher than would be expected for its 80° N location. This enables a variety of arctic species with more moderate temperature tolerances to thrive. The dense and diverse tundra and wetland vegetation in parts of the region, however, does not conform to polar desert or semidesert vegetation expected from the meager amount of precipitation (< 70 mm per year) recorded there. Comparisons between differing biological and geomorphological responses to the summer climatic regimes of 1988 and 1989 suggest a two source supply of moisture to the active layer in summer. Supplementary source of water, from the melting of massive ground ice bodies provides water from the base of the active layer, during the hot, dry summer of 1988. During the wet summer of 1989, a more conventional nival regime was in operation. These two potential sources of moisture in summer provide a fail-safe delivery system to vegetation in areas underlain by massive ground ice, and permit a richer vegetation growth than climate alone could.
Three occurrences of the macroalga Prasiola fluviatilis (Sommerf.) Aresch. were recorded after the examination of 32 stream segments from the Ellesmere Island National Park Reserve (81°23′ N) in the High Arctic of Canada. The collection sites were small (second‐third order) glacial melt streams characterized by pH 7.3–8.2, specific conductance of 52–159 μS·cm−1, low ion levels, extremely low nutrient levels, and the lack of other prominent macroalgae. These occurrences confirm the reported circumpolar distribution of the species.
A reconnaissance study of the vegetation of north-central District of Keewatin was undertaken in order to gain a better understanding of the relationships between the nature and distribution of plant communities and the surficial materials on which they grow. The
four types of surficial materials studied - bedrock, glacial deposits, marine deposits, and actively aggrading and eroding deposits - each support a suite of plant communities that naturally segregate on the basis of moisture regime. Bedrock supports solely cryptogamic communities. Glacial deposits,
commonly moderately to well drained, have lichen-heath and lichen-Hierochloe tundra; imperfectly and poorly drained glacial deposits have cryptogam-monocot tundra and wet sedge meadows. Marine silts and clays, generally moderately to poorly drained, support cottongrass tusscock tundra and wet sedge
meadows. The driest aspects are unvegetated or have sparse grass barrens. Marine sand and gravel are generally moderately to well drained and have shrub-monocot tundra or shrub-monocot barrens. Locally where poorly drained, wet sedge meadows occur. Communities growing on actively aggrading and
eroding postglacial fluvial and eolian deposits are generally in early stages of succession. Differences in species occurrence, abundance, and diversity, related to altitudinal and to some extent latitudinal changes, allow a bioclimatic subdivision of the Low Arctic ecosystem in the map area. This
zonation is most obvious in the changes from Zone I where there is a variety of heath species, a dominance of dwarf shrubs, and the regular occurrence of erect shrubs, to Zone III where lichens and masses are dominant and the importance of shrub species is reduced, particularly the absence of erect
shrubs and the reduction of heath species to two major ones. The removal or disruption of plant communities due to man's activities can lead to destruction of unique or botanically significant communities or species, alteration of drainage, accelerated geomorphic processes, and erosion. Such
activities can also lead to the destruction of important feeding and breeding habitats for de pendent fauna. Communities on imperfectly and poorly drained materials are the most vulnerable to disruption.
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