Skógræktarritið - 15.05.2001, Blaðsíða 140

podzol horizon contains 4.1%
(Ushakova, 1997).
Climate.
In general, the climate of the cen-
tral part of the province is more
continental than the climate of
the eastern and coastal parts
(Anon. 1965, 1968). The western
part has a higher precipitation,
than the central and coastal area
of the White Sea. The average
annual temperature is below 0° C
in the whole area, but inland and
at the White Sea it is clearly cold-
er than in the western region. The
western and coastal parts of the
region show evidence of maritime
climate by their reduced summer
rainfall (less than 35 % of the
annual distribution for June, luly,
and August)
Data collection.
Field work was carried out in
1990-1999 in the Khibiny, Keyvy,
Chuna-Tundra, Monche-tundra
and Salnye Tundry Mts. and
along the shore of the White Sea.
A total of 82 sample plots
(10 x 10 m) were made in birch
stands considered uniform in
floristic composition and struc-
ture. Percentage cover of each
taxon was estimated using the
following variant of the Braun-
Blanquet scale: « 1% cover, <
1%, 1-5%, 6-25%, 26-50%, 51-75%,
and 76-100%.
Altitude, aspect and slope were
estimated with the help of a map
and compass. Height and diame-
ter of trees were measured and
the density of canopy and cover
of understory species were est-
mated. The botanical nomencla-
ture follows Lid and Lid (1994)
for vascular plants, Ignatov and
Afonina (1992) and
Konstantinova et al. (1992) for
mosses and Santesson (1993) for
lichens.
In addition, birch forest vegeta-
tion samples taken by Avrorin et
al. (1935), Nekrasova (1938) and
Neshatayev & Neshatayeva
(1993) were included. These sam-
ples were comparable to Braun-
Blanquet releves.
Data analyses
The numerical technique
TWINSPAN, which gives both a
grouping of species and classifi-
cation of sample plots (Hill,
1979), was used to analyse the
more than 110 releves (stands).
Three levels of division were
taken into account in order to
produce the final community
units. The TWINSPAN sequence
of species was rearranged in
order to characterize the groups
of communities obtained in
terms of their floristic composi-
tion and to reveal clearly at a
glance the similarity and dissimi-
larity of samples.
Results
The two large groups delineated
by the first TWINSPAN division
corespond to heath and meadow
birch forests (Fig.l). Within
these, the following birch forest
community types were defined.
I. The Arctostaphylos uva-ursi type
of heath birch forest is widely
distributed at low elevations,
mainly on southerly plains. The
tree layer is open, with
policormic birches growing far
apart, and the field-layer consists
mainly of Arctostapfiylos uva-ursi
and Empetrum hermaphroditum.
Lichens of the genera Cladina and
Cladonia form the ground layer.
II. The Empetrum - Flavocetraria
type comprises the driest and
the most infertile birch stands.
They are common in the moun-
tains of the eastern part of the
province. The birches here grow
in bush islands, standing far
apart. Dwarf shrubs and chiono-
phobous lichens of the genera
Cladina, Cladonia and Flavocetraria
form scattered cover.
III and IV. The third group of
birch forests is where mosses
make up an essential part of the
ground-layer. Here birches are
often in the form of individual
trees, the stands occupying more
sheltered positions. There is a
dense ground layer with a large
proportion of mosses and liver-
worts, some vascular plants and
the constant presence of
mesophilous foliose lichens. This
group is divided into sub-units,
which differ in accordance with
the abundance of lichen and
moss in the ground layer; the
Empetrum - Cladina and Empetrum
- Hylocomium types.
V. The Empetrum - Cornus type
contains the transitional charac-
teristics of the heath to meadow
birch forest. These stands occupy
rather steep warm slopes with
good water supplies served by
numerous brooks. Polycormic
oblique birches form a dense
tree layer and the field layer con-
sisis mainly of herbs, although
dwarf shrubs are a significant
component too. The ground layer
is weakly developed (almost
absent). Owing to their particular
position and ecological condi-
tions these stands provide shel-
ter to some interesting rare Red
Book species such as Epipactis
atrorubens, Veronica fruticans and
Castillea lapponica.
VI and VII. The two last types rep-
resent meadow birch forests,
which are mainly situated close
to springs and rivers as well as in
mountains in the submaritime
zone, where meadow forests are
most prevalent. The birches here
are tall, straight or oblique.
Mountain ash and alder are com-
mon in the tree-layer. Luxuriant
tall herbs, grasses and ferns form
138
SKÓGRÆKTARRITIÐ 2001 l.tbl.