B. Papp szerk.: Studia Botanica Hungarica 33. 2002 (Budapest, 2002)

Dobolyi, Konstantin: Studies of vegetation dynamics on the rock grasslands in Csíki-hegyek (Budaörs, Hungary)

Table 9. Distribution of the nitrogen preference categories on the sites (BORHIDI 1993) (expressed in percentage). Nitrogen preferOdvas-hegy Szekrényes-hegy Farkas-hegy Kő-hegy ence categories 1996 2001 1996 2001 1996 2001 1996 2001 1 50.3 49.0 71.7 71.3 74.5 70.7 58.7 61.8 2 37.5 37.1 18.0 20.47 18.6 17.0 23.3 16.4 3 10.5 11.8 7.8 7.1 6.6 11.2 14.9 18.7 4 1.7 1.6 2.5 1.2 0.3 1.1 3.1 3.1 5 0.5 6-9 One potential kind of degradation is spreading of nitrophilous weeds in several vegetation types and distribution of the nitrogen preference categories can indicate nitrogen pollution of the environment. In our case low nitrogen preference is significant on the four sites. In Farkas-hegy the proportion of the higher nitrogen preference categories have been increasing in a small extent (Table 9). DISCUSSION Although we have no early data about the original vegetation of Csíki-hegyek, the main vegetation types could be: pubescent oak scrub woodlands, rock steppes, open and closed rock grasslands (ZÓLYOMI 1958). Most of the woods were cut several hundred years ago and the dolomite hills were pastured intensively. Proportion of the grasslands has increased in time, and their structure has • Odvas-hegy • Szekrényes-hegy • Farkas-hegy • Kő-hegy Fig. 1. Average naturalness value of the sites.