TITLE:
A Contribution to Pollen Rain Characterization in Forest-Savanna Mosaics of the Venezuelan Guayana and Its Use in Vegetation Reconstructions from Sedimentary Records
AUTHORS:
Leal Alejandra, Bilbao Bibiana, Berrío Juan Carlos
KEYWORDS:
Pollen Representation; Savanna-Forest Dynamics; Upland Guayana; Gran Sabana; Poaceae Pollen
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.7A,
July
18,
2013
ABSTRACT:
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.