Skógræktarritið - 15.05.2001, Síða 169

SKÓGRÆKT HANDAN SKÓGARMARKA / NSSE
FRANS E. WIELGOLASKI
Field- and bottom iayer vegeta-
tion mat transplantation:
A method to simulate possible
effects of climate change?
SAMANTEKT
Þökum úr bláberjalyngsmóum var umplantað yfir í þurra fléttuheiði,
en þökur úr henni voru færðar yfir í bláberjalyngsdæld 100-200 m í
burtu. Breytingar á gróðrinum voru skoðaðar eftir mislangan tíma.
Eftir 4 ár var minna en 20% af bláberjalynginu á lífi í fléttuheiðinni, en
eftir 9 ár einungis 10%, og fimmtán árum eftir umplöntunina voru engir
lifandi sprotar af bláberjalyngi eftir í hinni þurru fléttuheiði. Á runn-
fléttunni Cetraria nivalis (maríugrös), sem venjulega vex á vindsorfnum
hæðarbrúnum, gulnaði þalið hins vegar strax einu ári eftir umplöntun í
votari bláberjalyngsdæld. Þekja maríugrasanna minnkaði niður í 3-4%
eftir fjögur ár, og var einungis I % eftir níu ár, borið saman við þökur
sem var umplantað innan sama svæðis. Breyting á þekju annarra
tegunda við mismunandi umplöntun var einnig greinileg, en þó minni.
Votara loftslag með meiri snjó- og íshulu og styttra vaxtartímabili
getur haft svipuð áhrif og umplöntun á gróðurþökum úr þurri fléttu-
heiði í bláberjalyngsdæld með lengri snjóþekju, líkt og kom fram með
dauða maríugrasanna. Afturá móti geta loftslagsbreytingar sem valda
minni snjóþekju, kaldari vetrum og meiri þurrki haft svipuð áhrif og
sést á umplöntun bláberjalynggróðurs í þurra og opna fléttuheiði.
The climatic growth conditions
vary strongly over small distances
in mountains. Particularly, this is
true for the snow cover and the
soil moisture. Therefore, it may be
possible to simulate the effect of
climatic changes by reciprocal
transplantations of the vegetation
between nearby sites of different
soil moisture and snow cover.
In most cases transplantation
studies have been carried out on
single plant specimens, although
in some cases populations are
studied (Clausen et al., 1948;
Mooney and Billings, 1961;
McGraw, 1987). The reason is
that in most natural plant com-
munities it is not possible to
transplant the whole community
because of the size of the plants
both above and below ground. ln
many types of arctic, alpine and
sometimes subalpine plant com-
munities, however, this might
physically be done because of
the small plants found in the
field and bottom layer.
As a working hypothesis in the
present study it was expected
that the species growing in a
sheltered snow bed would be
more strongly influenced by
transplantation to a winter cold
and summer dry wind exposed
heath, than the species naturally
growing at that community, when
placed in a more sheltered and
moister snow bed. It was also
expected that the recovery would
be slower in the more strongly
stressed windswept heath than
in the snow bed.
Material and methods
Vegetation mats of two types of
low alpine plant communities at
the mountain plateau Hardanger-
vidda in southwestern Norway
(latitude 60°N, elevation I200m
a.s.l.) were chosen in the present
study, but similar transplanta-
tions could also been done in the
subalpine mountain birch forest.
One community was an olig-
otrophic heath dominated by
blueberries (a Phyllodoco-Vac-
cinion myrtilli community), one
of the most common communi-
ties in the region. It is found
where there is some snow protec-
tion from the lowest winter tem-
peratures and not too dry soil in
the summer. On the other hand
the vegetation period cannot be
too short, which means that this
type is missing also in extreme
snow beds. The other community
chosen was a typical oligotrophic
lichen heath (an Arctostaphyleto-
Cetrarion nivalis community),
common at dry, wind swept, win-
ter cold ridges.
The two communities thus
represent various climatic condi-
tions, although the horizontal
distance between them in the
field was only l-200m. It was
SKÓGRÆKTARRITIÐ 2001 1. tbl
167