Skógræktarritið - 15.05.2001, Blaðsíða 94

Fig. 1. Salix alaxensis after the storm:
surprisingly little damage.
age, and which recovered most
quickly, while taking into account
factors such as age, soil condi-
tions, etc. |Figs 1 & 2).
At the same time it became
important to convey a message
of optimism to people who were
perhaps filled with despair or
sorrow at the mess their trees
were in: "Don't worry, if your tree
is reasonably healthy and well
established it will recover in time
... take such and such precau-
tions ... and isn't it a good thing
you've got some tree shelterfor your
garden, otherwise the damage would
have been far, far worse."
Furthermore, an arborist could
hardly avoid thinking: "if certain
kinds of trees can survive such
weather conditions without
undue damage, why not use
them to shelter not only gardens
but agricultural crops as well?"
for there would have been signifi-
cant financial burdens incurred
by farmers and growers on that
day.
And one last thought: "Why is
it that some people who live in
Shetland go on insisting that
Fig. 2. Pinus contorta after the storm:
not so good-looking.
trees 'just don't or can't grow
here', when all the evidence
shows that they do - and can
stand up to phenomenal
extremes of weather?".
Pre-history
It has indeed often been said
that Shetland is empty of wood-
land because of the climate,
windiness being the prime cause.
Severe storms, however, damage
other vegetation as pointed out
above, yet the islands continue
to support a variety of grasses,
herbs and heather, as well as iso-
lated relict trees and shrubs, and
pockets of planted woodland
|Fig. 3].
Paleo-ecological research indi-
cates a sudden decrease of tree-
cover about 5,000 years ago
(lohansen 1985, Bennett et al.
1992). This appears to have coin-
cided with agricultural settle-
ment on a large scale. One need
only to look at lceland to see
how only 1200 years of human
occupation has severely reduced
tree-cover (The Forestry Fund
1994).
The late Professor David
Spence hypothesised that 5000
years of vegetation change was
as much due to animal grazing
and trampling as to climate
(Spence 1979). This followed a
period of initial burning and
felling, to which some Shetland
place-names deriving from Old
Norse bear witness, e.g. "Brunt
Hamarsland".
Remains of trees are found in
peat banks and in bogs, even on
quite exposed land. it is notable
also that the eight known surviv-
ing aspen (Populus tremula) in
Shetland, are all on cliffs
exposed to the Atlantic ocean
and its prevailing winds. While
one might imagine they had
been driven to the most inhos-
pitable locations by hostile
forces intent on their destruc-
tion, they nonetheless continue
to survive. Four of them have
now been brought into cultiva-
tion. It remains to be seen how
they grow in other more
favourable locations.
Likewise, Betula pubescens
(Downy birch), which was proba-
Fig. 3. Relict Sorbus aucuparia, Ronas
Hill, North Mainland.
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SKÓGRÆKTARRiTlÐ 2001 l.tbl.