Testate amoebae assemblages (Rhizopoda, Testaceafilosea, Testacealobosea) in bog habitats after effects of wild fires (south of Western Siberia)

Testate amoebae are numerous and crucial components of soil fauna. They are involved in food webs and play an important role in the biological cycle of substances. Testate amoebae are sensitive bioindicators of environmental change, even a brief and short one. The aim of our research was to analyze the features of the species structure of testate amoebae assemblages in bog habitats after severe wild fire exposure. The study objects were some burnt areas of pine-shrub-sphagnum bogs in the southern taiga subzone (Temnoye and Iksinskoye bogs) and the forest-steppe zone (Kuznetskii ryam) of Western Siberia (Figure 1, Table 1). At least 10 years have passed since the fire in the studied bogs, but the upper bog vegetation cover has not yet recovered to the previous condition. To analyze testate amoebae assemblages, we collected 32 samples of substrate from the bogs' surface. We washed samples of raw substrate weighing 4-5 g through the sieve (cell size of 0,355 mm) and put them aside for removing excess water. The resulting water suspensions were viewed under a microscope. We analyzed no less than 300 amoeba's tests in each sample and identified species composition and relative abundances. Also, we determined the density of testate amoebae assemblages in 1 g of air-dry substrate. On the whole, we revealed 50 testate amoebae taxa. The dominant species are Trinema lineare, Assulina muscorum, Trigonopyxis minuta and Corythion dubium. Species composition of testate amoebae assemblages varied in the studied burnt areas in different habitats: sphagnum, green moss and habitats with dead bog surface. Relative abundances of sphagnophylic species increased in moss habitats. In the burned areas of bogs, we observed a single occurrence of testate amoebae species, which are typical of minerotrophic fens (Cyclopyxis kahli, Heleopera petricola v. amethystea, Tracheleuglypha dentata, Trinema penardi) and mineral soils (Centropyxis aerophila, Cyclopyxis kahli, C. eurystoma, C. eurystoma v. parvula, Plagiopyxis penardi, Schoenbornia humicola). The species Cyclopyxis kahli is common both for fens and mineral soils. Testate amoebae assemblages in bog habitats after wild fire exposure are characterized by higher values of the Shannon diversity index and equitability. An increase in the relative abundance of species of the genera Trigonopyxis, Corythion, Trinema was observed in burnt areas of the studied bogs. The results obtained in our study are in good agreement with those of other authors who have studied the assemblage structure of testate amoebae in the mires and moorlands exposed to wild fire. A comparison of testate amoebae assemblages is made on the burned areas (severely disturbed habitats with dead bog surface) and areas with restored sphagnum cover (sphagnum habitats) within the same bog. Using the similarity indexes (Raup-Crick, Morisita) and the method of Coleman rarefaction we showed that species composition of testate amoebae assemblages is depleted in the disturbed habitats in contrast to the sphagnum habitats. We revealed changes not only in species composition, but also in relative abundance of species in assemblages. There was no significant reduction in the population density of testate amoebae on the disturbed habitats in comparison to sphagnum habitats.

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