DEEP-SOIL SPECIES OF COLLEMBOLANS AND IMPACT OF FIRE ON THE VERTICAL STRUCTURE OF POPULATION IN CHERNOZEM SOIL OF THE POPERECHENSKAYA STEPPE (BY THE MATERIALS OF THE “PRIVOLZHSKAYA LESOSTEP” NATURE RESERVE) 

Shveenkova Yuliya Borisovna, Candidate of biological sciences, senior staff scientist, State Natural Reserve «Privolzhskaya Lesostep» (12a Okruzhnaya street, Penza, Russia), jushv@mail.ru

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Background. Chernozem soil with natural steppe vegetation is highly structured, enabling collembolans to reach greater depth. Chernozem soils are distinguished by rare and deep-soil species of collembolans [1], that are met in single specimen and, as a rule, do nor breed to large numbers. However it is still hard to understand whether it is an accident when the certain species are discovered or they appear to be the permanent inhabitants of the deep layers of soil. The author counted collembolans in deep chernozem layers under a reedgrass meadow in 2000 and later in 2009. Due to the fire in the Poperechenskaya steppe in 2009 the author analyzed the pyrogenic factor influence on the collembolan population and its vertical distribution in chernozem soil.
Materials and methods. Vertical distribution of collembolans was investigated in chernozem soil under a herb reedgrass meadow of the Poperechenskaya steppe. In the spring of 2000 the researcher picked 80 probes of an area of 25 cm2 layer-bylayer (by 5–10 cm) from the wall of a 60-cm-deep soil profile. The accounting was repeated in the spring of 2009 (60 probes were collected at a depth of upto 50 cm), the probes were taken 1 month after the fire.
Results. In 2000 while deepening into the soil the author observed an irregular “step-by-step” decrease of the general density, species richness and quantity of separate species of collembolans. By the character of vertical distribution of mass species it is possible to single out three groups: the upper-soil, middle-soil and deep-soil one. While the second accounting in 2009 the author discovered the same deconcentration of collembolans in the soil profile. The compound of dominants had changed in the upper-soil and middle-soil groups, however in deep layers (30–60 cm) mass species of collembolans were recorded virtually in the same compound (Folsomia tatarica, Pseudofolsomia acanthella and Neonaphorura adulta dominates in both sampling, only Metaphorura affinis was replaced in 2009 by Micraphorura uralica). Virtually all deep-soil and rare species were discovered in the second accounting despite the fire.
Conclusions. The fauna specifics of the Poperechenskaya steppe includes rare and deep-soil species – Doutnacia xerophila Rusek, Folsomia dovrensis Fjellberg, Jesenikia filiformis Rusek, Jevania fageticola Rusek, Folsomia tatarica Martynova, Pseudofolsomia acanthella Martynova, Neonaphorura adulta, Granuliphorura ghilarovi comb. nov. (Khanislamova). Virtually all the above-mentioned species, except the last one, were discovered during the second accounting. Despite the effect of the pyrogenic factor, the collembolans, deconcentrated in the soil profile, kept the vertical differentiation of population. In consequence of the fire the greatest change in the compound and proportion of mass species of collembolans takes place in the upper-soil and middle-soil groups. On the contrary, the complex of species in the deep layers of chernozem soil was the least effected by the pyrogenic factor.

collembolans, chernozem soil, vertical distribution, fire, “Privolzhskaya lesostep” nature reserve.

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