Publikationen
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Behling, H. & Schüler, L. (2010): Characteristics of Poaceae pollen grains as a tool to assess palaeoecological grassland dynamics in South America. Vegetation History and Archaeobotany 20, 97-108.
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DOI: 10.1007/s00334-010-0264-0
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Abstract:
Abstract:
During the Quaternary, in particular during
glacial times, different grassland ecosystems played a
much larger role and had a significantly larger distribution.
Little is known yet about past development, biodiversity
and dynamics of grassland ecosystems. In this innovative
study, we attempt to distinguish between different South
American grassland types in space and time based on
morphological pollen grain characteristics of Poaceae. For
this purpose[60?80 Poaceae pollen grains of 20 grassland
samples were measured using their length, width and pore
diameter as well as annulus width. Samples were taken
from five sites in wet Pa´ramo vegetation from the Late
Pleistocene to the Late Holocene in South Ecuador and
from two sites in the south-eastern Brazilian highlands
(Campos do Altitude) of the same period. Additionally, we
investigated two samples from a Pampa site as well as six
samples from one Campos grassland site in southern Brazil
from the Late Pleistocene to the Late Holocene. Subsets of
samples of the Campos grasslands and of the Pa´ramo were
investigated in order to retrieve more detailed information
on patterns within these vegetation types. Multivariate data
analysis of the complete data set shows changes in taxonomic
composition along an elevational gradient in the
Pa´ramo grasslands. Our results reveal a highly dynamic
development of the individual grassland types; they also
provide interesting information on Poaceae taxa composition
patterns, development and possibly changes in
biodiversity within these ecosystems. Moreover, our data
provide an indication about the origin and dynamics of the
Campos ecosystems in the southern Brazilian highlands
during the Late Pleistocene and the Holocene before and
after the onset of human activities.
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Keywords: |
biodiversity |
grassland |
South America |
Poaceae |
pollen grain morphology |
grain size |
Pampa |
Schüler, L. & Behling, H. (2010): Poaceae pollen grain size as a tool to distinguish past grasslands in South America - a new methodological approach. Vegetation History and Archaeobotany 20, 83-96.
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DOI: 10.1007/s00334-010-0265-z
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Abstract:
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.
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Keywords: |
palynology |
grassland |
South America |
Poaceae |
Pampa |
Paramo |