The riparian vegetation of about 30 islands located upstream of lake Saint-Pierre has been analysed. Eleven natural vegetation units were identified, described and defined along with five units of human origin and six agricultural types. The aquatic habitat is characterized by a Vallisneria americana plant community-type. In the semiaquatic floodland habitats, four community-types were present: a Sagittaria latifolia, a Sparganium eurycarpum, a Phalaris arundinacea, and a Scirpus pedicellatus type. The wetlands were characterized by an Acer saccharinum – Ulmus americana – Fraxinus pennsylvanica forest. Both vegetational analysis and fluctuations of the superficial water table pointed to the existence of four variants in this last type of riparian forest. Those are respectively a Matteuccia struthiopteris, a Laportea canadensis, an Onoclea sensibilis, and a Rorippa amphibia variant. Granulometric and pedologie analyses of typical soil samples are also presented and discussed.
During the summer of 1979, indicator rabbits were placed in three sites in Entrelacs (Laurentian area, province of Quebec) and mosquitoes were collected in order to monitor arbovirus activity in the area. Eight seroconversions to California encephalitis (CE) group viruses were detected in rabbits during June, July, and August. Twenty-five strains identified as members of the CE group were isolated: 3 were obtained from viremic rabbit sera, 1 from adult Aedes communis reared in the laboratory from field-collected larvae, and 21 from mosquito pools. Twenty-two of these were typed as snowshoe hare (SSH) virus. No evidence of La Crosse (LAC) virus was detected but three strains belonging to the CE group showed antigenic properties different from reference SSH, LAC, or Jamestown Canyon (JC) viruses. One isolate identified as Flanders virus was obtained from Culex pipiens. Three mosquito species (A. communis, A. punctor, and A. excrucians) were involved in the transmission cycle of SSH virus in Entrelacs. This is the first report, in the province of Quebec, of SSH isolation from animal sera and the first demonstration of its transovarial transmission.
RésuméLa composition spécifique, l'abondance respective et la succession saisonnière des Tabanidae adultes sont analysées pour Poste-de-la-Baleine (55°17′ N; 77°45′ O) et le Golfe de Richmond (56°09′ N; 76°39′ O), deux régions de la toundra-forestière situées le long de la côte orientale de la mer d'Hudson. Un total de 14 espèces fut recensé à Poste-de-la Baleine (7 Chrysops et 7 Hybomitra) et de 8 espèces au Golfe (3 Chrysops et 7 Hybomitra). Six espèces sont holarctiques : C. nigripes, H. aequetincta, H. arpadi, H. astuta, H. lurida et H. frontalis. Les espèces les plus abondantes dans les pièges à Poste-de-la-Baleine (614 spécimens) sont : H. lurida (29.5%), C. furcatus (22%), C. excitans (18%), H. hearlei (11.9%) et H. frontalis (11%). Au Golfe, deux espèces dominent : H. frontalis (83.9%) et C. sordidus (12.2%). H. lurida est l'espèce la plus précoce; elle fut capturée en 1982 plusieurs semaines avant les autres espèces. Les résultats obtenus sont comparés aux rares études nord-américaines effectuées dans de telles régions.
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