|
Study: Avalanches along the Northwestern
slope of Todorka Peak, Pirin mountains
Aim of this Study is
to determine the most important limiting factors at the
treeline forests on the Northwestern slope of Todorka Peak,
Pirin mountains. It was a part of the PhD study of Eng.
Momchil Panayotov.
Pirin
Mountains are the second highest in Bulgaria (Vihren
peak, 2917m a.s.l.). The climate in the range is formed
under the complex influence of Mediterranean and Atlantic
air masses, with the predominance of moist Mediterranean
masses. This is reason for milder winters with frequent
snowfalls and occasional Southwestern winds. Due to its
specific climate Pirin Mountains have become refuge for
numerous plant species, many of which are endemic. This
is the reason why the majority of the northern part of the
range has been declared a national park and included in
UNESCO’s “Man and Biosphere” list of very important natural
zones. On the territory of the park are situated some of
the best-preserved forests of the Balkan endemic species
Pinus peuce and the very rare Pinus heldreichii.
Todorka peak (2748m a.s.l.,
41.45'N, 23.25'E) is situated in the central part of the
mountains , just opposite to the highest Vihren and Kutelo
peaks.
The Northwestern slope of Todorka peak with its numerous
avalanche tracks and couloirs descending through Macedonian
pine forests
The specific position
of the Northwestern slope of Todorka peak is the reason
for big snow accumulations. This, together with the fact
that the slope is with one of biggest vertical drops in
Bulgaria is the reason why it has very high avalanche activity.
On the slope there are eight major avalanche couloirs separated
by wide shoulders (ridges).
The middle and lower parts of the ridges are covered by
forests dominated by Macedonian pine (Pinus peuce
Griseb.) with limited participation of Norway spruce (Pecea
abies Karst.), Scots pine (Pinus sylvestris
L.) and Bosnian pine (Pinus heldreichii Christ).
The trees at the treeline are about 120-140 years old, while
those at the forests below reach up to several hundred years
(oldest found tree > 600 years).
Above the forests and along the borders of the avalanche
couloirs there are dense communities dominated by mountain
pine (Pinus mugo Turra ssp. mugo ) with
limited participation of small Macedonian pine trees, Common
juniper (Juniperus communis Willd. var. nana
), Goat willow (Salix caprea L.) and Mountain ash
(Sorbus aucuparia L.), White birch (Betula
pendula Roth) at lower altitudes.
Observations of forest
stands and single trees show that the highest zones of the
forests have been influenced periodically from falling avalanches.
The steep slopes and the fact that there are wide spaces
between the old trees contribute for the initiation and
falling of avalanches of different sizes in the forests
below the treeline.
The runout zone of one
of the couloirs. There are signs of huge avalanche
in the past (the ridge to the right of the couloir).
|
Taking cores from old
trees with the aim to build a "reference chronology" |
To determine the growth
differences between potentially influenced and not influenced
by avalanches trees there have been collected increment
cores from several different locations. One of them is at
the top of a slope where there is no possibility of avalanche
influence. On this place has been marked a permanent plot
and carried out measurements of tree diameters and heights.
The other trees, which have been selected for analysis,
are situated at treeline locations on the ridges between
the avalanche couloirs. For determining of the avalanche
regime and dating bigger slides, cores have also been extracted
from trees, which are situated on the borders of the avalanche
couloirs and in the runout zones.
Besides influence from
avalanches the trees in the forests at the treeline and
below it experience periodic influence from big snowfalls
and possibly accumulation of rhyme and ice. There have been
observed occasions with breakage of the top of the stems
of smaller trees and big branches of old trees after intensive
snowfalls.
Since the slope is lee to the prevailing strong Southwestern
winds they are not from the most important limiting factors
for the growth and development of the trees.
The collected
data from filed measurement and observations have been inserted
in GIS, which facilitates composition of thematic maps,
filed work and future research in the specified regions
and sites.
Up to this moment there
have been built Reference chronology and the major avalanches
in two couloirs have been dated.
Publications:
Panayotov, M.P. and
Yurukov, S. (2007) Tree ring chronology from Pinus peuce
in Pirin Mts and the possibilities to use it for climate
analysis. Phytologia
Contacts:
Dr. Momchil Panayotov,
e-mail: panayotov.m@ltu.bg
|
