Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
the greatest importance to prove o ur views. The present paper originates
from this difference of opinion, but it has also anot her and more general
aspect — i.e. the deyelopmental history of Swedish spruce forest treated with
the periodic storm-gaps and their regeneration as the central theme.
Certain soils, such as those upon which in Fennoscandia the spruce forest
is the climax, are unstable, and the forests on them consequently subjected
to storm-felling. For instance, marly moraines in Uppland produce soils of
this type, as do also the morain fields in Uppland and Gästrikland which are
composed of large boulders of local origin, often piled up in ridges (p. 36—48).
Storm-felling in spruce forest on marly moraines has been described
previously by Hedemann-Gade and Lubeck, mainly from a technical and
economic point of view. The present author deals particularly with the
forests on boulder moraines. It is emphasized for the first time that these
soils are particularly favourable to the spruce in preference to other plant
communities, and, further, that such spruce forests are easily devastated by
storms and gales. The forests of Granskär and Fiby stand on just this type
of boulder morain.
Storm-felling is to be regarded as one of the catastrophic ecological
changes (catastrophic destruction, Tånsley). The author, having studied the
storms and their effects in Uppland from 1795 up to the present time (p. 17),
considers storm-felling a periodic phenomenon. Uppland seems to have
suffered at least 17 storms of such violence that the spruce forests must have
been ravaged along the path of the gale. It would not seem too daring to
suppose that every spruce forest on unstable ground within the province has
been exposed to at least 5 such storms each century. Over large areas in
Uppland gaps were made in the same spruce forests both in February 1932
and in December 1931 ; so that storm-gap formation is evidently a secular
factor of great importance.
One must, however, aseertain whether the storms in question have really
been of such violence that the gap-formation has reached the dimensions
and intensity required by the author’s theory of storm-gap regeneration.
For this purpose historical and statistical details are given for the
cata-strophies of 1795, 1931 and 1932. Some of the figmres of Hedemann-Gade
and Lubeck, for the counties of Stockholm and Uppsala, are quoted in the
table on p. 32 for the 1931 storm-felling which is one the best studied
statistically. Protective measures on a large scale had to be taken then to avoid
an economic disaster in wide areas.
However, this damage in 1931 seems inconsiderable compared to that of
the 1795 eatastrophy. This one devastated an area more than three times
greater — we know of its effects from Southern Gästrikland, practically the
whole of Uppland and large parts of Västmanland — and it was of such
terrific violence, that much even of the forest on the stable soils was
over-thrown.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
