Soil nematodes of coniferous forests in the Finnish-Russian Friendship Nature Reserve

Abstract

The article describes the communities of soil nematodes in pine (hereinafter – Pinus sylvestris) and spruce (hereinafter – Picea abies) forests in the Finnish-Russian Friendship Nature Reserve. It exemplifies typical north-taiga forests and combines Kostomuksha State Nature Reserve (Republic of Karelia, Russia) and Friendship Park, consisting of five Protected Areas in the adjacent area of Finland. Methods commonly applied in nematology were used to study the following parameters: taxonomic diversity, population density, biomass, eco-trophic structure of nematode communities, and ecological indices representative of the soil food web. In the coniferous forests, the soil nematode fauna was made up of 45 nematode genera belonging to 29 families, with the highest diversity demonstrated by bacterial feeders (42% of the total number of taxa detected). Coniferous forests in the Finnish territory featured a high number of taxa (29–33) and high values of the Shannon index (Hʹ) (3.4–3.8) as compared to their counterparts in the Kostomuksha State Nature Reserve (18–24 taxa and Hʹ = 2.4–3.3, respectively). A general trend for all the surveyed forests was a decrease in nematode abundance and biomass from the forest litter towards the mineral soil layer, which was more pronounced on the Finnish territory. A Principal Component Analysis of relative abundance of functional guilds of nematodes showed that forests of Eastern Finland had a more uniform nematode fauna among soil horizons. Analysis of the eco-trophic structure of nematode communities in soils under the coniferous forests revealed a high abundance of bacterial feeders, fungal feeders and nematodes associated with plants, while plant parasites were scarce or missing. In pine forests of both Russian and Finnish parts of the Friendship Nature Reserve, soil nematode communities were noted for a higher diversity and relative abundance of predators, while those in spruce forests had a higher abundance of fungal feeders than in pine forests. The regional features of the nematode fauna in the Kostomuksha State Nature Reserve were a low diversity and high dominance levels of taxa (high Simpson's index values), low maturity index (ΣMI) and structure index (SI) of the nematode communities, possibly as a result of human impact or other local-scope adverse environmental factors. The forest nematode communities in the Finnish territory showed a higher diversity of the fauna and a lower dominance level of taxa (a more evenly structured nematode fauna). The Finnish forests harboured 16 specific taxa not encountered in the Russian territory and plant parasites of the family Trichodoridae, which were rare in Northwest Russia. In addition, the group of dominant taxa included K-strategy nematodes sensitive to the environmental conditions. All this suggests that the conditions on the Finnish side are more favourable for soil nematodes. The ecological indices explored in the study (SI, EI) confirm that Finnish coniferous forests are stable habitats with complex, multicomponent soil food webs and undisturbed soil ecosystems. On the contrary, the indices for forests of the Kostomuksha Stare Nature Reserve betray a simplified and unstable food web associated with degraded soil ecosystems exposed to detrimental environmental impacts.

Keywords

• eco-trophic structure
• ecological indices
• population density
• protected area
• soil nematode community
• taxonomic diversity