FLOOD AS STRESS WHICH INCREASES THE NATURAL VALUE OF THE DEPRESSIONS OF ARABLES ON THE HUNGARIAN BODROGKÖZ

Generally the agrarian habitats are extremely poor in floristical elements with high natural value. The lack of oxygen kills most of the cultivated plants in the flooded depressions and in its muddy fringes. This hypoxic stress makes bare soil surfaces free from competition which are favorable for aquatic and amphibian plant-communities. During our coenological and floristical investigations of Hungarian Bodrogköz (Szirmai et al. 2008) micro region (NE Plain), there are seven protected plant species have been found from the 69 natural species of the flora of flooded depressions. We have explored four associations which were new for the territory of Hungary. TheElatinetum alsinastri(Nagy et al. 2006). (dominated by the protectedElatine alsinastrum) and theVeronico anagalloides-Lythretum hyssopifoliae(Wagner ex Holzner 1973). Belong to theNanocyperionassociations, and theOenanthetum aquaticae(Nagy et al. 2006). andButometum umbellati(Konczak 1968) (Philippi 1973). belong to theOenanthion aquaticaeassociations. All of the four associations are mono-dominant, herbaceous community, built by native species. They appear as the early state of secondary succession of agrarian habitats and appear as scattered small islands with more or less natural vegetation in the so called „rural deserts”. Altogether the flood stress decreases the profitable size of plough-land but increases the natural value of it.