Kitaibelia vol. 3 – no. 2. (1998) p.335-336.
Állapotváltozások a Hortobágyi Nemzeti Park löszgyepeiben (1981-1994)
V. Sipos Julianna
In grazed loess swards the number of constant-subconstant species is usually smaller than in the not or only very extensively grazed ones. The low proportion of the constant species proved to be the most evident in the case of island-like sites of small extension on the top of the "szik-benches" (Máta, Villongó). At the early 90's, the number of the constant-subconstant species showed a further decrease in some areas. In the relevés of this area in the year 1992 were missing some typical "good" loess grassland species, as e.g. Ajuga genevensis, Astragalus austriacus, Salvia austriaca, Stellaria graminea, Thalictrum minus. Festuca rupicola, Euphorbia cyparissias, Galium verum as constant species, can tolerate the grazing. The cover of the following forbs have decreased: Dianthus pontederae, Filipendula vulgaris (disappeared), Fragaria collina, Thymus marschallianus. The cover of Salvia nemorosa was only slightly decreasing, but we could find mostly only clonal sprout-colonies. The same phenomenon was observed also in Phlomis tuberosa. The grazing has restricted some weeds, as well, but Cardaria draba was increasing (nitrophilisation). The loess grasslands proved to be rather sensible against all types of disturbances, including the wrong management, as well. The good quality of loess grasslands can only be sustained, if we could conserve the closed grass cover. All kinds of influences which discontinue the closed grass cover, proved to be harmful. Hence, the concentration and stationing of the livestock on smaller patches results in a heavy degradation due to overgrazing, -trampling and -dunging. The grazing of the loess grasslands must be only a very extensive one, and it can be carried out only by traditional races of cattle or sheep, with regular moving of the livestock. The removing of the dung cannot solve the problem of degradation, because the gaps caused by tramping and overgrazing, immediately will be re-colonised by weeds from the seed-bank of the soil. Thus, the selective eradication of weeds and the mowing of grasslands must be combined. The alkali grasslands - on the other hand - proved to have a rather high resilience against disturbances. In the Festuca pseudovina swards we could not observe any evident tendencies of compositional change. Puccinellia limosa showed, however, an expressed extension into the fescue swards and it has overgrown some patches of the bare "blind-szik", as well.