2015

Permanent URI for this collectionhttps://hdl.handle.net/1807/67833

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    Flowering and fruiting responses to climate change of two Arctic plant species, purple saxifrage (Saxifraga oppositifolia) and mountain avens (Dryas integrifolia)
    (Canadian Science Publishing, 2015-10-01) Panchen, Zoe; Gorelick, Root
    In temperate regions there are clear indications that spring flowering plants are flowering earlier due to rising temperatures of contemporary climate change. Temperatures in temperate regions are rising predominantly in spring. However, Arctic regions are seeing unprecedented temperature increases, predominantly towards the end of the growing season. We might, therefore, expect to see earlier flowering of later-season flowering Arctic plants. Parks Canada has been monitoring purple saxifrage (Saxifraga oppositifolia) and mountain avens (Dryas integrifolia) flowering and fruiting times for 20 years at Tanquary Fiord, Quttinirpaaq National Park, Ellesmere Island. S. oppositifolia flowers in early spring, while D. integrifolia flowers in mid-summer. Over the 20 year period, Tanquary Fiordâ s annual and late-summer temperatures have risen significantly. During the same timeframe, D. integrifolia showed a trend towards earlier flowering and fruiting, but S. oppositifolia showed no changes in flowering or fruiting time. Flowering time was related to monthly temperatures just prior to flowering. The number of flowers produced was related to the previous autumnâ s monthly temperatures. We found no relationship between flowering time and snow melt date. Our findings suggest that Arctic community-level ecological effects from climate change induced phenology changes will differ from those in temperate regions.
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    Diversity patterns in subarctic stream benthic invertebrate assemblages from the Sahtu Settlement Area, Northwest Territories, Canada.
    (Canadian Science Publishing, 2015-06-28) Giberson, Donna J; Vinke, Kristen; Medeiros, Andrew Scott
    Benthic invertebrate assemblages were studied across four streams in the Sahtu settlement region of the Northwest Territories (NWT) between July 2010 and October 2011 to provide information on biotic composition and associations with habitat and temporal factors. Overall diversity was similar for all streams, though taxonomic composition varied among the streams. Within streams, richness was highest in riffle and snag (woody debris) habitats, and lowest in pools and leafpacks. A substantial portion of taxa (~25 %) would have been missed if only riffles had been sampled. Nearly 88 % of individuals belonged to eight taxa, with > 60 % of individuals found in only two families (Chironomidae and Baetidae). While high within-family diversity was observed, samples were also characterized by large numbers of rare taxa, with large temporal differences in abundances. Future benthic assessments in northern streams would benefit from increased sampling effort to ensure representative samples for comparing streams or sites, and approaches that target dominant families in the north (e.g. Chironomidae), which can provide a great deal of information on biodiversity when examined at the generic level. Likewise, further analysis of the seasonal compositional turnover for some assemblages may be necessary to distinguish anthropogenic responses from natural variability.
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    Carbon exchange over four growing seasons for a subarctic sedge fen in northern Manitoba, Canada
    (Canadian Science Publishing, 2015-09-06) Hanis, Krista L.; Amiro, Brian D.; Tenuta, Mario; Papakyriakou, Tim N.; Swystun, Kyle A.
    Net ecosystem exchange of carbon (NEE) was measured using eddy covariance for four growing seasons at a subarctic hummocky fen in northern Manitoba, Canada. Over a 115-day measurement period each year, cumulative NEE ranged from a gain of 49 g C m-2 to a loss of 16 g C m-2 with a mean loss of 6 g C m-2 from the fen, with an uncertainty of about Âą34 g C m-2. Ecosystem respiration decreased with higher water tables (r2=0.3), especially in one summer when flooding occurred to 0.12 m above the peat surface. Additional methane emissions previously documented for the site of 4 to 5.7 g C m-2 y-1 added to the carbon loss. Carbon loss was measured from this same fen in the 1990s and it is likely that the carbon gain (peat accumulation) during past centuries has not continued in recent decades. Scaling to annual greenhouse gas emissions as a 100-year global warming potential showed that this fen is currently a source of 192 to 490 g CO2-equivalents m-2 y-1 based on both carbon dioxide and methane flux measurements, indicating that peat is decomposing.