Zs. K. Komáromy szerk.: Studia Botanica Hungarica 17. 1984 (Budapest, 1984)
Siklósi, Engelbert: The flora of the pits in the Nature Preservation Area of Ócsa
S T U D I A XVII. BOTANIGA HUNGARICA (Antea: Fragmenta Botanica) 1984 p. 41-54 The flora of the pits in the Nature Preservation Area of Ócsa By E. SIKLÓSI (Received November 30, 1982) Abstract: The flora of 5 pits and a canal in the protected area of Ocsa were examined. A total of 140 cenological sample plots in these areas were studied and their floras compared. The previous rarest species are missing from the vegetation of pits but their re-establishment could be expected in the former place. INTRODUCTION The pits examined by me are situated in the Nature Preservation Area of Ocsa, which were turned over to the custody of the NAEPNC in 1975. This area covers 3575 hectares and lies between the villages Ocsa, Dabas and Inárcs, in Pest country. Out of this 1412 hectares the areas known as "Öregturján", " Nagy túrj án", Rókás erdő strictly protected. The above-mentioned mine lakes are situated in the area of "Öregturján". Origin of the area and geological construction The P.A. of Ocsa lies about 30 km SW from Budapest and east of the Danube valley. The surface (loess, wind-blown sand) formed in the Pleistocene was partly destroyed by the Danube in the pre-Holocene that widened its bed to the east. In this way a characteristic bog area developed in the formed depression. The regulation of waterways partly changed the nature of the bogs but fortunately could not completely change it. The subsoil water of the high, sandy and loess hills and the seepage coming from the shelf of the hills of the Danube-Tisza Mid-region ensured the continuance of the bogs. The late-Pleistocene gravel transporting and containing water added to the rich water supply that is near the surface (IVANYOSI 1979). The remaining parts are "Öregturján" W of the village Ocsa, "Vörös-ér" and "Rokás-mocsár" SE of the village and "Nagyturján" N of village Sári. At the lakes and periodically flooded areas are found the boggy meadow soils. The character of this soil is the stong hydromorphic effect. The soil profile may be wet, or saturated with water all over the year. Airless anaerobiosis and the accompanying reductive effects influence in decisive way the determinant processes of soil formation. A result of these effects is the formation and accumulation of turf. The upper layer consists almost completely of turf, it is alkaline, as shown by dam and snail shells in it. The turf is formed by reed ( Phragmites communis ) and sedge ( Carex spp.). The turf layer is as high as 1 meter near the village Őcsa (SZABOLCS 1979). The character of the area outlined above was formed by the specific interrelation of soil and water. The agricultural drains of the area were built several decades ago. The subsequently modified drains lead to the already completed section of the Danube-Tisza channel and to the Danube I
