Vol 74, No 1 (2019)

A detailed study of the vegetative–detrital cover (VDC) of pine ecosystems of the Mari Zavolzhye demonstrated that, depending on its origin, a specific hydrothermal soil regime is formed in each type of forest. It has been established that the VDC has the highest moisture capacity in lichen–mossy pine forests in comparison to lichen–pine forests. For the first time, based on the VDC parameters, a scale has been proposed to estimate the rate of the biological cycle. It is established that the most important indicators are the thickness of the VDC, ash content, and hydrolytic acidity.

The paper presents research data on profiles of fatty acids in typical chernozems of various use. It is shown that organic matter degradation in typical chernozems is accompanied by depletion of fatty acids, while its accumulation results in an increase in their diversity. In this regard, the composition of fatty acids in soil profiles makes it possible to classify soils with respect to predominant organic matter transformation processes. It has been revealed that the distribution of fatty acids in soil aggregates of different sizes is inhomogeneous in uncultivated chernozems, but homogeneous in developed soils. Eicosapentaenoic acid, which is a moiety of microalgae, and dihomo-gamma-linolenic acid, which is synthesized by Mortierella fungi, can be considered biomarkers of the transformation of cultivated typical chernozem into abandoned land.

Roadside soils along Leningradskoe Highway are ecotoxicologically assessed by the laboratory phytotest method based on two test cultures. The research was carried out along a 300-m-long transect established perpendicular to the highway. The toxicity of soils, determined according to inhibition of the growth parameters of Lepidium sativum L. (cress) and Hordeum vulgare L. (rye), has been revealed in the majority of the studied area and is characterized by a bimodal distribution: it is maximum at a distance of several meters from the highway (dangerously and moderately toxic soils), sharply decreases at a distance of 7 m from it, and gradually increases again towards the end of the studied zone (moderately toxic soils). The degree of phytotoxicity is differentiated depending on the test culture variant: H. vulgare was characterized by a lower sensitivity to pollutants and did not reveal toxicity in the 7–25 m zone from Leningradskoe Highway, while L. sativum revealed toxicity of soils throughout the investigated area. Among the analyzed test parameters, root and seedling length were the most sensitive to pollutants, while seed germination was uninformative.

Direct and inoculation methods indicated high concentrations of bacteria on the following plants: Carex nigra, Eriophorum vaginatum, Drosera rotundifolia, and Ledum palustre. The correlation between bacterial abundance, species, and organs of the studied plants was revealed. Proteobacteria were shown to predominate in the phyllosphere, while bacilli and actinomycetes prevailed in rhizoplane and rhizosphere. Members of the genera Pseudomonas and Erwinia predominated in the phyllosphere. High values of the nitrogen-fixing activity of bacterial populations in the rhizosphere were revealed, which reached a maximum in the rhizosphere under sundew.