Soil Nematodes of Northern Meadows and Agrocoenoses as Bioindicators of the Transformation Degree in Soil Ecosystems

Abstract

This paper examines the effect exercised by agricultural intensity on soil nematode communities inhabiting natural meadows, hayfields, and monocrop agrocoenoses in the Republic of Karelia. The diversity of the soil nematode fauna in natural meadows is similar to that in hayfields, but it significantly decreases in agrocoenoses. The abundance of nematodes reaches the highest values in soils of meadows and decreases as land use intensity goes up. Bacterial feeders predominate in the eco-trophic structure of nematode communities in all types of biocoenoses reaching the maximum share in agrocoenoses. The relative abundance of predators and nematodes associated with plants in agrocoenoses is significantly lower compared to natural meadows and hayfields. Ecological indices computed for nematode communities indicate the presence of a stable and multicomponent soil ecosystem in meadows. The CI index reflecting the predominant pathway of organic matter decomposition indicates an active participation of bacteria in the destruction. Values of the SI and CI indices decrease in agrocoenoses, while the EI index increases. Such a ratio between indices specifies simplified food web and a disturbed soil ecosystem in agrocoenoses. Discriminant analysis shows that, of all studied biocoenoses, only agrocoenoses and natural meadows can be differentiated statistically significantly based on differences in the SI index. However, the identified positive effect of latitude on the SI index in agrocoenoses indicates that the application of this parameter to northern ecosystems has some limitations.