The effect of crops cultivation on the soil free-living and plant-parasitic nematodes in agrocenoses of southern Karelia (fields with tilled crops, artificial grasslands) was studied. A comparison of monodominant plant communities in agrocenoses (tilled crops) and cenoses with alien species Heracleum sosnowskyi Manden was made. The characteristics reflecting the features of nematode communities in different types of agrocenoses were established. They include faunal composition with identification of constant and specific taxa determining the similarity/differences between agrocenoses, trophic structure of nematode communities, and ecological and population indices facilitating the assessment of soil ecosystem state. Bacterial and fungal feeders resistant to unfavourable conditions dominate under tilled crops and take part in organic matter decomposition, forming the core of the nematode fauna. In seeded meadows plant feeder nematodes become more significant in the community. The values of ecological and population indices show that the soil ecosystem is structured and stable. According to the characteristics of soil nematode communities the agroecosystem of the polycomponent seeded meadow corresponds to a late stage of ecological succession.