Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 51. (Budapest 1959)
Kovács, L. ; Gozmány, L.: Data to the quantitative relations of the Lepidoptera of the Alderwood Marshes in Ócsa, Hungary
Data to the Quantitative Relations of the Lepidoptera of the Alderwood Marshes in Ocsa, Hungary By L. KOVÁCS and L. GOZMÁNY, Budapest We began our surveys, to be discussed hereafter, on 10 June 1952 in the alderwood marshes which stretch in a broad zone East of the Danube, from Alsónémedi toward Dabas. The site of the surveys lie in the vicinity of Ócsa, about 5 km to the S — SE of the inhabited area. The selection of the site was based on the expert findings of our botanist colleague P. J a k u c s, for whose kind help to further our work we have the pleasant duty to express our gratitude also in this place. Two points of view decided on the selection of the above site. One of them was that its approach should not be overly difficult, and the other that, in spite of this, the plant associations in the given area should bear as little traces of human interference as possibile and as circumstances permit it. We found an area conforming to the above requirements near the Babád road, in the so-called Nagyerdő (Great Forest). This forest is partly a pure alderwood, partly mixed with hornbeam ; — to designate it phytocoenologically, a Cariceto clongatae Alnetum glutinosae, that is, its Fraxinus excelsior consociation. The trees are tall, healthy, about 25—30 years old at that time. In the spring, the ground beneath the trees is inundated with the exception of some higher points ; whilst, in the dry summer season, the surface layers in contact with the atmosphere show some traces of desiccation, but even a slight disturbing of the soil brings also wet ground to the light. Aerial humidity is always high during the night. The compact foliage hinders considerably evaporation, slowing down thereby also the rate of drying up of the soil. During the summer, the temperature of the forest is much more uniform than that of the adjacent marshy fields, since the foliage tempers insolation during the daytime as well as the loss of warmth in the night. Due to this fact, the formation of dew will often fail to take place beneath the trees when it is abundant in the fields or even in the clearings within the forest. With the commencement of the late summer falls in temperature, climatic differences will gradually increase between the forest and the marshy fields in the daytime hours, since the nocturnal losses in temperature of the forest could be replaced less and less under the close foliage. The shrub zone beneath the trees is represented mainly by Sambucus nigra and a Rubus species. The spreading of the black elder is indubitably the result of human interference. In several places, Humulus lupulus climbs high up the trees. There is no grass zone in the strict sense of the word, Gramineae
