Saturday, 15 July 2006

The Soils Cover of the Volcanic Area from the Eastern Carpathians (Romania).

Constantin Rusu1, Iulian Stanga2, Lilian Niacsu2, Iuliana Breaban1, and Bogdan Rosca1. (1) Univ Al l Cuza, Faculty of Geography and Geology, Iasi, 700505, Romania, (2) Univ AI I Cuza, Faculty of Geography and Geology, Iasi, 700505, Romania

This morpho-structural unit occupies the western part of the Eastern Carpathians (Romania), which extends to north across the border in Ukraine and to south till the Perşani Mts. The genesis of the longest inactive volcanic chain from Europe (almost 200 km length) has been synchronous with the folding of the Neogene Carpathian flysch, in three tectono-magmatic cycles, in Badenian, Upper Sarmatian–Lower Pliocene and Upper Pliocene–Lower Pleistocene. The specific of these manifestations, their age and the differentiated aerial modelling, hand in hand with the bio-climatic characteristics has allowed the delineation of the Oaş-Văratec, Ţibleş-Bârgău and Călimani-Harghita sectors. The Oaş-Gutâi-Văratec Mts, located in the north-western extremity and formed in the conditions of a late subsequent magmatism, were individualized during the first two tectonic cycles, through aerial and underwater eruptions. Their reduced altitudes (under 1450 m) and the accentuated relief fragmentation impose an extreme complexity of the soil forming processes. The Ţibleş-Bârgău group belongs to a volcano-sedimentary area, in which the lava flows alternate with sub-volcanic corps (Ţibleş-Hudin) and with large sedimentary areas. The medium altitudes and the litologic diversity determine the complexity of the soil cover. The Călimani-Gurghiu-Harghita Mts are the most recent sector, the highest (2101 m in the Călimani Mts) and with the most typical volcanic features. The soil forming processes are characteristic to a mountainous temperate and boreal climate, and to diverse vegetation associations. The litologic background has been analysed with the help of the geological maps (1:50000) and of own field research. In the north-western (Oaş-Gutâi) and central (Ţibleş-Bârgău) areas, the effusive and intrusive magmatic rocks do not overrun 50% of the surface, while in the southern compartment (Călimani-Harghita) the volcanic rocks clearly dominate (varieties of andesites, dacites, riolites, basaltic andesites and basalts). Besides these are encountered different pyroclastic and derived deposits. The litologic complexity and the landscape variety determine a specific grouping of the soil forming processes, on the background of a thermal differentiated (0-8șC) and relatively humid (600-1200mm/year) climate. The relief is interesting through the partial maintenance of volcanic apparatuses, of lava levels, the considerable extension of the volcanic plateaus, the existence of varied dimensioned calderas, as well as through the lacustrine evolution of some areas. Soil diagnosis was based on the field data (over 150 profiles), according to the Romanian Soil Taxonomy System (Bucharest, 2003). The realization of the soil maps was done using modern cartography techniques (TNTmips 6.9 software). The soil study shows the existence of a diversified soil cover. The latitudinal zonation is not obvious, yet the soil cover presents a clear tendency of altitudinal zonation. Another reference element is the anthropic intervention. In these conditions, the soil cover comprises typological entities grouped in 9 soil classes (from the 12 separated on the Romanian territory). The zonal soils belong to the Cambisols (Eutric and Dystric Cambisols), Podzols (Entic, Haplic and Umbric-entic Podzols) and Umbrisols (Humic Umbrisols), with altitudinal limits varying according to the rock chemistry. The presence of eruptive materials determines the occurrence of Andisols, while in the peripheral areas characteristic are the Luvisols (Haplic Luvisols, luvic phases, Luvisols). Between the soils related to lithology we mention the Vertisols and vertic subtypes, with isolated occurrences at the region's periphery. In the conditions of pluvial hydromorphism Gleyosols and stagnic subtypes are developed, which in special conditions may evolve till the stage of Histosols. On small surfaces occur Leptosols, Regosols, Fluvisols, diversified at typological level. The anthropic modified soils belong to the Anthrosols and eroded phases of different soil types. The most representative are the soils with andic character (Andosols and andic subtypes), while the Cambisols become dominant on the lower part of the landscape (under 1000m). The Spodisols occupy the range over 1400 m (20% of the territory), while the Umbrisols have local occurrences. The soil cover of the Eastern Carpathian volcanic area shades a few types of landscape, most representative being the forested ones (broad-leaved forests under 1200m, beech-coniferous mixing and coniferous between 1200 to 1800m). To these are added the secondary mountainous (with acid soils, poorly productive) and subalpine (over 1800m) meadows, and some surfaces strongly affected by man.

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