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A Contribution to Pollen Rain Characterization in forest-savanna Mosaics of the Venezuelan Guayana and Its Use in Vegetation Reconstructions from Sedimentary Records

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American Journal of Plant Sciences 2013年第7期4卷 33-52页

作者： Leal Alejandra Bilbao Bibiana Berrío Juan Carlos Department of Environmental Studies Universidad Simón Bolívar Sartenejas. Edo. Caracas Venezuela 2Department of Geo- graphy University of Leicester Leicester UK.

The main results of a study of pollen representation in surface soils from different plant communities in the upland savannas of Guayana were presented. The representation of savanna herb pollen mainly belonging to the Poaceae and Cyperaceae was high in open communities such as fernlands, grasslands and Mauritia palm swamps, but decreased as vegetation structure became more closed and woody;from savanna-forest borders to secondary forests and lastly, evergreen montane forests;mimicking the gradient of vegetation openness observed in living plant communities. Thus, the proportion of savanna herb pollen in herbaceous communities: swamps, fernlands and grasslands, reached over 80% and arboreal pollen contributed less than 10%. This ratio changed in savanna-forest borders where savanna herb pollen decreased to 60% or less and the proportion of arboreal pollen rose to 30% or higher. Lastly, in forest soils, pollen abundances from trees (Dimorphandra, Protium, Schefflera), shrubs (Miconia and other Melastomataceae) and lianas contributed higher than 60% of the pollen sum, even in open gallery forests and fallows. The lack of pollen from cassava, the main crop in the forests of the region, at these sites was remarkable. The ordination of sediment samples from 4 records from the Late Holocene with respect to the soil surface samples studied, showed that the characterization of pollen rain was useful for identifying long-term compositional and structural changes in the sedimentary records, thus providing objective indicators for the interpretation of past vegetation structure.

关键词： Pollen Representation savanna-forest Dynamics Upland Guayana Gran Sabana Poaceae Pollen

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