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  • Richard, Pierre J. H.  (3)
  • 1
    Online Resource
    Online Resource
    Consortium Erudit ; 2020
    In:  Le Naturaliste canadien Vol. 144, No. 1 ( 2020-03-17), p. 63-76
    In: Le Naturaliste canadien, Consortium Erudit, Vol. 144, No. 1 ( 2020-03-17), p. 63-76
    Abstract: The postglacial history of the present-day black spruce and balsam fir-dominated bioclimatic domains of boreal Québec and southern Labrador (Canada) was reconstructed using 61 pollen diagrams from lake sediments. The period, deglaciation geography and climate determined whether or not there was an initial tundra vegetation. The establishment of trees and the subsequent development of forest cover were largely a function of climatic changes and the varied occurrence of fire over time. Afforestation was diverse, with numerous vegetational landscapes lacking modern analogues. Their duration was varied, with certain species showing extreme cases of cornering and effusion, both in space and time. The establishment of forests similar to those found today was gradual. As the climate warmed, there was an increase in the abundance of relatively thermophilous species. This progression culminated between 8,000 and 4,000 years ago. Climatic deterioration then caused a regression of the vegetation cover, giving rise to the present bioclimatic domains.
    Type of Medium: Online Resource
    ISSN: 1929-3208 , 0028-0798
    Language: French
    Publisher: Consortium Erudit
    Publication Date: 2020
    detail.hit.zdb_id: 2477916-7
    detail.hit.zdb_id: 2658776-2
    detail.hit.zdb_id: 207093-5
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Consortium Erudit ; 2007
    In:  Géographie physique et Quaternaire Vol. 50, No. 3 ( 2007-11-30), p. 331-340
    In: Géographie physique et Quaternaire, Consortium Erudit, Vol. 50, No. 3 ( 2007-11-30), p. 331-340
    Abstract: Erstaunlich hohe Pollen-Konzentrationen wurdem im Till in der Nâhe des Kraters von Nouveau-Québec festgestellt (Richard et al., 1991; Frechette 1994). Wir haben die Hypothèse aufgestellt, daB das nahe bei der glazialen Eisscheide gelegene Till reicher an Pollen ist, als die von ihr entfemten Tills. Die Hypothèse wird in diesem Beitrag ûberprùft. In der Tat enthâlt das Till aus dem Zentrum von Nunavik nahe bei der glazialen Eisscheide Pollen-Konzentrationen der GrôBenordung -31 000 Korner/g, wogegen die mehr Ôstlich und westlich gelegenen mittlere Werte von -8500 Kôrner/ g bzw. -6800 Korner/g haben. Die Sedimente aus dem Zentrum von Nunavik konnten vor einer intensiven glazialen Erosion bewahrt werden, so daB der wâhrend der vorher-gehenden lnterstadiale und Interglaziale angesammelte Pollen erhalten und wieder-verwendet werden konnte. Auf den ersten Blick entsprechen die Pollen-Spektren vom Till der Halbinsel Nunavik ungefàhr der heutigen Biogeographie. Die Pollen-Einheiten vom mehr nôrdlichen Till scheinen eine Pflanzen-Tundra zu spiegeln, wogegen diejenigen vom sudlicheren Till eher einer Busch-Tundra gleichen. Die Analyse der Hauptbestandteile erlaubte die Polleneinheiten des Tills mit denen der Oberflàchensedimente der umliegenden Seen zu vergleichen. Die Ergebnisse heben das Fehlen gegenwàrtiger Entsprechungen hervor und lassen auch Unterschiede in der Verteilung oder Ausbreitung der bioklimatischen Zonen im Vor-Wisconsinium erkennen.
    Type of Medium: Online Resource
    ISSN: 1492-143X , 0705-7199
    Language: French
    Publisher: Consortium Erudit
    Publication Date: 2007
    detail.hit.zdb_id: 2035245-1
    SSG: 14
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  • 3
    In: International Journal of Wildland Fire, CSIRO Publishing, Vol. 19, No. 8 ( 2010), p. 1026-
    Abstract: The hypothesis that changes in fire frequency control the long-term dynamics of boreal forests is tested on the basis of paleodata. Sites with different wildfire histories at the regional scale should exhibit different vegetation trajectories. Mean fire intervals and vegetation reconstructions are based respectively on sedimentary charcoal and pollen from two small lakes, one in the Mixedwood boreal forests and the second in the Coniferous boreal forests. The pollen-inferred vegetation exhibits different trajectories of boreal forest dynamics after afforestation, whereas mean fire intervals have no significant or a delayed impact on the pollen data, either in terms of diversity or trajectories. These boreal forests appear resilient to changes in fire regimes, although subtle modifications can be highlighted. Vegetation compositions have converged during the last 1200 years with the decrease in mean fire intervals, owing to an increasing abundance of boreal species at the southern site (Mixedwood), whereas changes are less pronounced at the northern site (Coniferous). Although wildfire is a natural property of boreal ecosystems, this study does not support the hypothesis that changes in mean fire intervals are the key process controlling long-term vegetation transformation. Fluctuations in mean fire intervals alone do not explain the historical and current distribution of vegetation, but they may have accelerated the climatic process of borealisation, likely resulting from orbital forcing.
    Type of Medium: Online Resource
    ISSN: 1049-8001
    Language: English
    Publisher: CSIRO Publishing
    Publication Date: 2010
    SSG: 12
    SSG: 23
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