HELMINTHOLOGIA, 38, 2: 105-109,2001 Soil and plant nematode communities of two types of ecosystems B.VALOCKÁ,M.SABOVÁ,M.RENCO Parasitological Institute of the Slovak Academy of Sciences, Hlinkova 3,040 Ol Košice, Slovak Republic Summary Abundance of soil and plant nematodes and the nematode communities structure were compared in natural perma- nent grass ecosystems and regularly cultivated cereal agro- systems at four localities in East Slovakia. The mean num- ber of genera and the abundance of nematodes were higher in cereals. Plant feeders were the dominant trophic group at all localities in both types of ecosystems. Helicoty/en- chus spp. were the most abundant plant parasitic nemato- des with higher population densities on permanent grass stands. Ty/enchorhynchus, Merlinius and Praty/enchus we- re more abundant on cereals. Bacterial feeders were the subdominant trophic group at the majority of the localities, the fungal feeders at the locality with acid environment. The least abundant trophic group were the predators. Eco- logical and nematode communities indices used for evalua- tion of the studied ecosystems indicated higher stability of the natural grass ecosystems. Key words: nematode communities; trophic groups; natu- ral grass stand; agroecosystem; cereals; Slovakia Introduction Soil and plant nematodes are important components of both natural and cultivated ecosystems. Nematodes are known as primary consumers (plant parasites),secondary consumers (predators) and consumers of decomposters (bacterial and fungal feeders) and they are involved in soil ecological processes such as decomposition, mineralization and nutrient cycling. Because of differential sensitivity of nematodes to environmental disturbance, they provide an indication of the diversity or stability of soil ecosystems. Ecological aspects of the occurrence of nematodes, their role in soil processes, as well as the possibility and utility to use the nematode community analysis as a measure of the condition of soil environment are presented in many recent studies (Wasilewska, 1997, Bongers and Bongers, 1998; Ritz and Trudgill, 1999). Nematode community structures have been studied mostly in natural and semi-natural ecosystems. In agroecosystems the interest concentrated on plant parasitic nematodes as crop pests. In both types of ecosystems soil and plant nematode communities are influenced by various biotic and abiotic factors, such as plants, soil type, land and crop management. The changes in the structure of nematode communities are expressed in ecological indices (Yeates and Bird, 1994; Bongers et a/., 1997; Bongers, 1990, 1999; Yeates, 1999). In our previous work we studied the changes in the struc- ture of trophic groups and values of some indices in natural grass lands in regions of East Slovakia with different pol- lution levels (Valocká and Sabová, 1997a). The aim of this study was to compare the nematode com- munities structure of natural permanent grass ecosystems and regularly cultivated cereal agroecosystems. Material and Methods Investigations were carried out in 1999-2000 at four locali- ties in the East Slovakia region. At each of the localities two neighbouring sites - with natural permanent grass stands and cereal crops were selected. Locality Polov - situated in Košická kotlina Basin, 21° 12' E, 48° 40' N, altitude 230 m, soil pH 6.6-7.0, mean annual rainfaIl 522 mm, mean annual temperature 9.4°C. Grass site: covered with grass - legumes multispecies as- sociation. Cereal site: 1999 winter wheat, 2000 spring barley. Locality Jelšava - situated in Revúcka vrchovina High- land, 20° 4' E, 48° 38' N, altitude 260 m, soil pH 7.0- 8.3, mean annual rainfaIl 572 mm, mean annual temperature 9°C. Grass site: covered with grasses with dominance of Agro- pyrum repens. . Cereal site: 1999 winter wheat, 2000 winter wheat. Locality Nižná Slaná - situated in Revúcka vrchovina 105