Scots pine is well represented
throughout the historical records of the British Isles,
except during some glacial stages (Godwin, 1964). The
fossil records fluctuate frequently in many pollen diagrams,
allowing us to
establish the changing status of pine throughout history.
However, due to its tendency to travel long distances
it can be a problematic guide to the local presence in
an area. Abundant macroscopic evidence has been accumulated;
wood, bark, needles and cones have been discovered at
sites to produce trustworthy records of the past occurrence
of pine near or at the site of their recovery. On mainland
Europe there is the possibility that these remains may
have belonged to other species, but in the British Isles
there is no reason to suppose that during the Holocene
period any other species other than Pinus sylvestris was
present.
In the past it is believed to have occupied two different
types of habitat similar to those that it inhabits today.
It is highly characteristic of the transitional stages
of vegetational succession which correspond with the initiation
of raised bog above fen. During the late stages of fen
consolidation, fen-carr or fen-wood is established, which
are first rich in Alnus and Betula and later Quercus and
Fraxinus. However, if the region favours the colonisation
of base-tolerant Sphagna on the floor of the fen-wood
than the floor can become increasingly
acidic. It is at this stage that that Pinus sylvestris
largely replaces other trees, although over time can also
succumb to water logging due to the continued accumulation
of Sphagnum (Godwin, 1964).
The second habitat type favouring pine preservation, are
the direr portions of raised bogs and blanket bogs, which
may occur as the result by drainage of ancient peat cuttings.
Although today pine may be sparse in such areas, there
is evidence from past periods of climatic dryness where
there has been a marked
invasion of Betulus and Pinus, pine in particular tolerating
the high acidities developed by the weathering of Sphagnum
peat. Layers of pine stubs have been found indicating
dryness in the Sub-boreal period. When pollen analysis
has been carried out in such pine layers in raised bogs,
pollen curves have shown maximum pine pollen, because
the increase in pine was local and therefore confined
to the bog surfaces, not affecting the general composition
of the countryside (Godwin, 1964).
The Compared to other trees its productivity is very high;
although the large size of the grain increases fallout,
this is offset by the fact that its density is very low
because of the lateral air sac. Therefore the observed
rate
of fall in still air is the same as some unwinged, smaller
grains. The grains are particularly liable to long-distance
transport, which can explain why pine pollen appears in
areas where it is never likely to have grown. The grain
is quite resistant to decay and is often preserved in
mineral sediments where other pollen has since decomposed.
The air sacs give them buoyancy and float on water, often
forming a yellow film during pollination (Godwin, 1964).
There are records for all 4 sub-stages of the Hoxnian
interglacial and the preceding late glacial, and can be
correlated with abundant macroscopic evidence. There are
records for the early and late Weichselian and Ipswichian,
and during the Holocene, zone 1v it is common throughout
the British Isles forming a wide spread local presence
of about 10-20%. |
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