Fjölrit RALA - 15.06.2004, Page 84

Environmental conditions of Andosol formation in Transylvania
(Romania). Soils of the Gurghiu volcanic chain.
S. Jakab1, G. Fuleky2and O. Fehér2
Sapientia Hungarian University ofTransylvania, Faculty ofTechnical and Human Sciences, Targu Mures
2Szent István Universiyt, Department ofSoil Science and Agrochemistry, Gödöllo, Hungary;
The area of our case study is located in the Cálimani -Gurghiu-Harghita volcanic chain in the
Westem part of the East Carpathians.10 sites were investigated in details during July and
August of 2003.
This volcanic chain is the youngest volcanic area of the Carpathians and the length’s of it is
approximately 160 km. The volcanic activity started in the northem part in the Cálimani
Mountains, roughly some 9.5 million years ago. On the basis of K-Ar dating the age of rocks
of the central part of the volcanic chain, the Gurghiu Mountains, is of about 7,2 million years
(Szakács-Seghedi.,1995), whereas the last emptions of the southem Harghita Mountains (at
Mt. Ciomadul [Csomád]) occurred only some tens of thousands years ago (Pannon
Encyclopaedia, 1999). As a consequence of its young age, the volcanic edifices of the chain
are well preserved. The region is still showing post-volcanic activity. According to
Michailova et al., 1984, Pécskay et al., 1985, Seghedi et al. (in print): the whole massiv of the
Gurghiu Mountains, both petrologically and geochemically can be considered homogenious
and mainly built up of pyroxene-andesites.
The starting point of our toposequence is the top of Seaca (nSOm)^ famous for its superbly
oval caldera. The Seaca is built up mainly of lava flows and pyroclastic sequences. The the
foothill areas of the volcanoe are composed of more or less reworked secondary products
intercalated between pyroclastic fall and flow deposits and subordinate lava flows (Pannon
Encyclopaedia, 1999).
The slopes of the cone of Seaca are dissected by the streams of Sovata, Nyárád, and
Gurghiu rivers. Surface mnoff at the study area is limited due to dense vegetation cover and
very high drainage of the soil surface horizons. Only are occuning along the forest roads and
sheep-tracks.
Present day climate is mainly influenced by three main factors: continentality, significant
vertical elevation differences and the north-south orientation of the mountain ranges.
According to 20 years measured average the precipitation varies between 800-1200 mm and
mean annual number of days with snow cover may reach 200 days. The typically north-south-
oriented mountain ranges experience a great amount of annual precipitation especially on
their westem side, from the prevailing westerly winds. The mean annual temperature is
around 3.5°C. Elevation differences may cause significant changes within short distances. The
mean annual number of frost days may exceed 160-180 even in the basins.
From the point of view of soil formation all the above mentioned climatic conditions are
favouring strong leaching and intensive weathering processes.
The other factor of understanding of soil genesis at our study was the influence of the
paleoclimate: an extension of the last (Wiirm) glaciation, when the whole region was
dominated by periglacial climatic influences, the rejuvenation of the surface was possible.
Vegetation cover at the elevations of 600-1200m is mainly beech forest (Fagetum
carpaticum (Soó, 1935) mixed with Picea abies and grass-cover (Oxalis acetosella, Galium
odoratum, Dentaria glandulosa , Luzula albida, L. sylvatica), Circaea alpina) conditions.
Above 1600m vegetation mainly composed of: Pinus mugo and ocassianly species of Picea
abies appears. The grass cover composed of Vaccinium myrtillus, V.uligimosum, Festuca
rubra and Nardus stricta.
65