Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)
Kisbenedek, T.: Habitat preference and seasonality of spider (Araneae) communities in dolomitic grasslands
Direct evidence has been found (GUNNARSON 1990) that the habitat structure affects the abundance in spider species dwelling on conifers. COLEBOURN (1974) also proved the effect of habitat structure on certain changes in the abundance of net-spinning species. In the present paper the structure of a spider community is demonstrated in dolomitic grasslands. Habitat preference and seasonal distribution in the diurnal and nocturnal types of wandering hunters have also been studied. STUDY AREA Data were collected in the vicinity of Budapest, in the Buda Hills (47° 35' N, 18° 90' E). The study area was outlined on the Odvas Hill, which is situated 10-12 kilometers west of Budapest, close to the settlement of Budaörs. The Odvas Hill is a 315 meter high, eroded barren karst with steep slopes. Its basement rock is mainly dolomite, with some loess at the southern foot of the hill. Around the peak the soil is immature. Low quality brown forest-soil can only be found on certain parts of the hill. The surface that seems to be barren from a distance, is covered by grasslands flowering in various colours during spring and summer. Natural vegetation occurs only on these spots and around the peak. There are orchards and vineyards on the slopes together with introduced black pine forests. Three grassland associations were studied: (A) open slope dolomitic grassland (Chrysopogono-Caricetum humilis), dominant grass is Carex humilis and the Chrysopogon gryllus and other steppe grass species. The cover of vegetation is 50%. (B) ecotone zone between the two grasslands A and C, with species coming from the two associations. Its vegetation cover is 70-80%. (C) closed dolomitic grasslands (Festuco pallenti-Brometum pannoniéi), its dominant grasses are Bromus erectus, Carex humilis, Festuca pallens. The cover of vegetation is totally closed (based on JAKUCS 1981). The microclimatic conditions are the most balanced in the grass at the northern slope - its climate is cool, while the grass at the south-southwest has the warmest microclimate (PÉCSI 1958). METHODS Data collection with pitfall traps was carried out from April to October in 1988.108 traps were set up in 3 groups with 36 traps in each groups. The 3 groups were situated along a straight line: the first in patch A, the second in patch B, and the third in patch C. The distance between the first and second groups was 100 m while it was 300 m between the second and third. Each had a triangular shape. Cylinder shaped plastic cups were used with the volume of 3 dl for trapping. The cups were covered with iron sheet and they were filled with ethylene-glycol as killing agent which was supplemented fortnightly. Diversity was calculated by the Shannon-Weaver function: H = - Zpi In (pi) where H = Shannon-Weaver index, pi = relative frequency value of the i species, In = natural logarithm. Dominance value was calculated by the BERGER-PARKER index (1970): D = Nmax/N where D = dominance value, N m ax = maxium abundance value of species, N = total abundance. Richness index was calculated according to MARGALEF (1958): R = S -1 / In (N) where R = Margalef s richness index, S = total number of species, N = total number of individuals, In = natural logarithm. Evenness index was calculated according to PIELOU (1975): E = H/In (S) where E = evenness index, H = Shannon-Weaver index, S = total number of species, In = natural logarithm.
