| The macrofossil evidence for
Filipendula ulmaria is considerable, consisting
of carpels that have lost their outer coat and have an
asymmetric twisted form, crescentic in the side view and
are quite recognisable when in this form and also when
entire (Godwin 1975). They are also distinguishable from
Filipendula vulgaris. The pollen grains of the
two Filipendula species are not readily distinguishable
and so fossil pollen records are not separated beyond
the genus level. The recovery of Filipendula pollen
in association with F. ulmaria macrofossils (Godwin
1975) encouraged the general attribution of fossil Filipendula
grains to F. ulmaria, although some may well be
F. vulgaris. Filipendula pollen has been
recorded in all phases of all interglacials since the
Cromerian (oxygen isotope stage 11) and in all sub-stages
of the subsequent interglacials. Pollen records also occur
from earlier interglacial contexts and from the early
and late phases of glacial cold stages (Godwin 1975).
Filipendula pollen is present in significant percentages
in both the early and middle Devensian, but reaches high
frequencies during the Devensian Late Glacial period and
the transition to the Holocene. Although Filipendula
is a high pollen producer, the evidence suggests that
it was abundant during these periods, as it occurs in
almost every site investigated and often in high percentages.
Godwin (1975) notes that F. vulgaris is characteristic
of present day cold steppe grassland and so the Devensian
records may be referable to that species. The abundance
of marshy habitats suitable for F. ulmaria in the
Late Devensian, however, supports that as the species
responsible for Late Glacial Filipendula abundance,
especially as Filipendula ulmaria is today an important
component of the kind of tall herb vegetation communities
which were typical under Late Glacial environmental conditions.
Great reductions in pollen frequencies for Filipendula
during the cold and arid Late Devensian Stadial also suggest
that F. ulmaria was the species involved. Filipendula
ulmaria is also regarded as a thermophilous plant
and was abundant in the early tall herb stage of transitional
vegetation succession towards shrub and tree cover at
the start of the Holocene. Such short-lived successional
population expansion of thermophilous taxa on base-rich
soils after climatic amelioration is typical of protocratic
phase vegetation before tall shrub and tree expansion
occurred (Birks 1986). The temporary high frequencies
of Filipendula pollen will reflect the abundance
of the plant around shallow lakes and marshes where it
would be locally dominant in the earliest Holocene. Filipendula
pollen is present throughout the rest of the Holocene
in low frequencies and the species remained present in
wetland communities as it does today. Higher pollen frequencies
in the later Holocene are probably due to a spread of
wetland habitats with climatic deterioration and are most
apparent at sites in western parts of the British Isles
(Godwin 1975). Clearance of woodland would have assisted
that change and also increased the flowering and pollen
transport of Filipendula. The pollen record indicates
a probably continuous presence of Filipendula in
the British Isles through several glacial/interglacial
cycles (Godwin, 1975). |
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