Abstract:
Despite the dominance of grasslands during the
last glacial period, especially in South America, the highly
uniform morphology of Poaceae pollen grains has so far
allowed only very few palynological studies based on
Poaceae pollen. In our study we compare two methods of
distinguishing between South American grassland ecosystems
based on quantitative morphology of Poaceae pollen
grains. We investigated data sets from Pa´ramo in southern
Ecuador, Campos de Altitude and Campos in south-eastern
and southern Brazil as well as data sets from the Pampa in
Argentina by measuring the pollen grain length, grain
width, pore diameter and annulus width. Firstly we investigated
the potential influence of chemical treatment of
pollen grains on pollen grain size as well as the measurement
setting for defining the boundary conditions for using
Poaceae pollen grains in a palaeoecological investigation.
Finally the measured pollen grain parameters were analyzed
by comparison of average grain length using
statistical tests. This approach reveals highly significant
differences in average grain size between all grassland
ecosystems. Assuming that a certain grain size range can
be assigned to a certain Poaceae taxon, conclusions about
differences and similarities in taxa composition can be
derived. We used two methods of multivariate data analysis.
One uses the pollen grain parameters directly for a
Principle Component Analysis (PCA). The other is an
already established method in grassland ecology which
defines parameter based pollen grain types to investigate
similarities between grassland ecosystems. Both approaches
confirm the results of the grain length analysis. In this
work we demonstrate that the method we developed has the
potential to provide acquisition of so far inaccessible
information on spatial and temporal patterns and dynamics
of South American grasslands.
