A pollen diagram from a small lake in the region of Chibougamau (49°41′N, 74°35′W; elevation 380 m), central Quebec, is divided into four pollen assemblage zones. Before 7600 BP the landscape was open shrub tundra and the pollen input to the lake was primarily from long-distance sources. Larix, and to a lesser extent Populus, were important colonizers of the newly deglaciated land, and Picea was also present. Betula papyrifera and Picea dominated the open forests between 7600 and 4700 BP. After 4700 BP the forest became more dense and the importance of Betula papyrifera suggests relatively warm and dry climatic conditions. Around 3900 BP Picea, Ericaceae, and Sphagnum increased in abundance at the expense of Betula, suggesting cooler, wetter conditions. Pinus banksiana increased during this period but was never very abundant. The modern boreal forest thus developed relatively late in this region and has been present for only the past 2000–3000 BP. Key words: paleoecology, Quebec, Holocene, boreal forest, Betula papyrifera, Picea.
Vegetation changes during the Holocene in the North Iberá, Corrientes, Argentina. Wetlands are very important sites for palynological studies, since they represent one of the most suitable environments for fossil pollen preservation. The aim of this work was to determine, by palynological analysis of lacustrine sediments, the vegetal communities and the predominant environment during the Holocene in NW of Iberá. Two lagoons were studied: San Sebastián and San Juan Poriahú. Sediment samples were obtained with witness using a "Levingstone square-rod sampler", processed with Faegri e Iversen techniques and dated with C 14. The palynological graphs were divided in zones using the Tilia program. The palynological analysis allowed visualizing diverse changes in the vegetation: from 6 140±50 to 5 170±100 a. C., the NW of Iberá was characterized by marsh-herbaceous vegetation and arboreal vegetation typical of dry vegetation. From 5 170±100 to 3 460±60 a. C., a decrease in the species frequency, typical of wet environments, is produced, and the clogging of the waterbody, from 3460±60 a. C. onwards, while continuing the dominance of herbaceous vegetation typical of these environments, the arboreal pollen, indicates the beginning of a hygrophilous forest development. Rev.
En el presente trabajo se analiza el contenido del tracto digestivo de picudos capturados en cuatro localidades de la provincia de Formosa, Argentina: Laguna Blanca, Palma Sola, Laguna Naik Neek y Buena Vista durante el período junio 1995 - mayo 1997. De los 647 picudos disecados, el 70 % presentó polen en el tracto digestivo. Se registraron 2.404 granos de polen que fueron agrupados en 37 tipos polínicos pertenecientes principalmente a las familias Malvaceae, Compositae, Solanaceae y en porcentajes inferiores al 1%: Euphorbiaceae, Amaranthaceae, Leguminosae y Polygonaceae. A lo largo del período estudiado, la ingesta de granos de polen fue muy variable, aunque pudo observarse una tendencia a una menor ingesta durante los meses de invierno. Las posibilidades de alimentación, unidas a las condiciones climáticas y la presencia de Gossypium hirsutum L., su más importante hospedante reproductiva, y Cienfuegosia drumondii (Gray) reconocida como hospedante reproductiva silvestre, favorecen la actividad del picudo durante todo el año.
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