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A bstract: Tlie species composition, nest density, structure and ecological profile of an ant community were studied within a transect encompassing the forest interior, forest edge and a belt-shaped clearing in a moist mixed pine forest habitat (Querco roboris-Pinetum) in the Kampinos Forest (Central Poland) in the context of direct and indirect human impact and the bioindicator importance of ants. Altogether, 19 ant species were found; the most abundant ones (in respect of number of nests) in the entire habitat under study were Temnothorax crassispinus (Karav.) and Myrmica rubra (L.). All analysed parameters of individual subcommunities, except for nest density (highest on the forest edge, lowest in the cleared belt), showed a gradient pattern of variability, with species richness and the index of general diversity increasing and the dominance index decreasing within the transect from the forest interior to the cleared belt. Differences between the two subcommunities from the forested area (forest interior and forest edge), both highly dominated by T. crassispinus, were, in every way, much smaller than those between either of them and the subcommunity from the cleared area, where M. rubra prevailed.

Key words: earthw orm s, m onocystid gregarines, Apicom plexa, in fection, parasites, heavy m etals, u rbanization, Warsaw. i n t r o d u c t i o nA m odern c ity possessing vast green areas is generally stated to be an ecosystem in w h ich the basic elements o f its s tru c tu re and p rin cip le s of fu n c tio n in g are s im ila r to those o f n a tu ra l ecosystems ( P i s a r s k i and T r o j a n , 1 9 7 6 ; G e p p , 1 9 7 7 ) .The u rb a n iz a tio n o f an area involves m a n y serious im pacts on b o th abiotic and b io tic com ponents o f the environm ent. Besides changes in tro p h ic and c lim a tic re lations, those proceeding in soil belong to the m ost im p o rta n t. Hence, in order to assess the degree o f u rb a n stress, soil a nim als are often used as bio ind ica tors. N a tu ra lly, b io ind ica tors are m a in ly searched am ong the m ost susceptible so il anim als, however, some representatives o f the n o n susceptible ones m ay also be occasionally u tilize d fo r the purpose o f b io in d ica tio n . E a rt hw orm s are o f th a t type due to th e ir ca p a b ility to accum ulate poisonous

Tom 37Warszawa, 30 IV 1995 Nr 18 N . K u z n e t s o v a , M . S t e r z y ń s k a E ffects of single trees on the com m unity structure of soil-dw elling Collem bola in urban and non-urban environm ents Abstract. Species composition and com m unity stru ctu re of Collembola com m unities u n d er the crowns of single trees were studied in non-urban and urb an environm ents in order to reveal their possible significance in spatial organization in open biotopes. In a n atu ral environm ents single trees may play an im portant role acting as refugia for forest species as well as a norm al h ab itat for some eurytopic meadow forms. In urban habitats, the effect of single trees on collembolan com m unity organization is m uch weaker. The ecotone effects of single trees is also discussed.