Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)

Dobolyi, K., Kováts, D. , Szerdahelyi, T. ; Szollát, Gy.: Vegetation studies on the rocky grasslands of Odvas Hill (Budaörs, Hungary)

rence appears also in group IL Here the N2 value is the highest. According to the categories of the preservational indexes (Fig. 9) we could mention the relative poorness of protected species, the higher quantity of the natural pioneer (TP), natural disturbance tolerating (TZ) and weed species (GY) of group II. The constancy values (Table 2) of the four sample groups are given according to ZÓLYOMIS data (1958). (The typical open dolomite grass communities marked by Zl and the stipetosum eriocaulis-pulcherrima subassociation marked by Z2. Having compared the data it could be established there are no essential differences between the Odvas Hill samples (mainly groups III and IV) and the typical (Zl) association. From the missing species in ZÓLYOMI'S list Botriochloa ischaemum may be noteworthy from the Odvas Hill southern side sample groups I and IV with constancy value IV (natural disturbance tolerating species) and the Orthantha lutea (therophyton species) indicating degradation. Anthyllis vulneraria also occurs with higher constancy value in sample groups II and III (natural disturbance toleranting species). Mainly the presence of this plant with high coverage value supported the separation of the stand spots marked 3 on the sketchy vegetation map originally based on an air photo. SUMMARY As a result of investigation of the open rocky grasslands, existing especially on the northern facing slopes of Odvas Hill we concluded to the following. On the southern (-southwestern) and southeastern facing steep slopes there is an open dolomite rocky grassland community (Seseli leucospermo-Festucetumpallentis ZÓLYOMI (36)66) having an extraordinary value from the nature conservancy point of view. Fortunately this stand is degraded only to a small degree (groups I and IV of samples) (see Fig. 10). On the steeper parts of the western (-northwestern) slopes of the hill there are also existing open dolomite rocky grassland community stands, characterized by masses of Anthyllis vulneraria in some places. On the steep eastern (-northeastern) slopes on the eastern part of the hill there is a smaller patch of the stand having the same physiognomy (group III of samples). On the less steep slopes exposed to the west there are markedly and slightly degraded open dolomite rocky grassland community stands (group II of samples). Our investigations revealed, that in the case of sample groups III and IV the inclination of the slope has a greater influence on the development of the vegetation than its exposition (see groups III and IV of samples). The richness of the vegetation in rocky grassland elements - Festucetalia valesiaceae - (Fig. 4) and the relatively high number of Mediterranean and sub-Mediterranean -, as well as Pontic, Pannon and Balkan elements (Fig. 5) in these open dolomite rocky grassland communities is natural. The relatively high number of species having chamaephytonous and nanophanerophytonous life-form is characteristic (Fig. 6) and the higher number of termophilous species on the south-facing slopes (Fig. 7) is also typical. The high number of xerophilous species is living on basic soil being poor in nitrogen was also expected (Figs 7, 8). The number of the protected species is relatively high, too (Fig. 9). The constancy values of our samples generally corresponded with Zolyomi's (1958) drawn tables. The high constancy values of Botriochloa ischaemum and Anthyllis \%ilneraria - native species that tolerate disturbance - as well as Orthantha lutea - species of principal component, native to the area - indicate degradation. * * * Acknowledgements - The authors are grateful to L. LÓKÖS for collecting and identifying the lichens growing on Odvas Hill and drawing up the list of the lichen species, to B. PAPP and DR. M. RAJCZY for having done the same with the mosses. We would like to express our thanks to J. DÓRÁN and J. ESZTERGÁLYOS for their assistance given in drawing of illustrations and in preparing the data. This study was made within the framework of the Succession Research Project", an OKKFT programme of the Hungarian Natural History Museum supported by the OMFB.