Soil nematode communities of typical biocoenoses in the republic of altai

The first data on soil nematodes of coniferous forest and steppe biocoenoses in the Republic of Altai are presented, thus making it possible to establish relationships between different characteristics of nematode communities and vegetation features. Overall, 49 taxa of soil nematodes belonging to 31 families and 9 orders were found. The results showed the highest value of nematode taxonomic diversity lying in larch forest, vs the lowest in steppe biocoenoses. The nematode population density and biomass were similarly high in the soil of forest biocoenoses, but significantly exceeded those in the steppe. Variations in the eco-trophic structure of soil nematode communities among the study biocoenoses were revealed. In the pine forest with Pinus sibirica, bacterial feeders and nematodes associated with plants prevailed in the soil, this being typical of various types of pine forest, vs bacterial feeders, plant parasites and fungal feeders which dominated the larch forest. Nematode communities in steppe soils showed specific features and differ markedly from those in forest biocoenoses, the community structure being incomplete, with dominance of fungal feeders and/or omnivores. Based on ecological indices (Structure index SI, Enrichment index EI) calculated for nematode communities and the state of the food web described, the soil ecosystems of forest biocoenoses were assessed as undisturbed, with complex food webs and a moderate level of soil organic matter enrichment. The steppe biocoenosis formed by Stipa splendens, on the contrary, was characterized by low SI and EI values indicating a simplified and unstable food web associated with degraded soil ecosystems under the influence of unfavorable environmental factors (climatic or anthropogenic). This shows a possible effect on soil nematodes of the extreme conditions formed in the steppe of the Kosh-Agach region. The CI index values of the predominant pathway of organic matter decomposition in the soil varied depending on biocoenosis type. In Siberian stone pine and larch forests, low CI values were found, indicating an active participation of bacteria in the destruction of organic matter in the soil. This is not typical of forest biocoenoses of other zones (for example, coniferous forests of Karelia), where soil fungi dominate the decomposition of organic matter. In this study, high CI values were observed in the steppe biococenosis, indicating the dominance of soil fungi in the processes of organic matter destruction.