The article highlights the consequences of the Chernobyl disaster. Northern Polesia has been and still remains the most polluted area. Full scale and limited economic activity is carried out on part of the contaminated territories. The zone of radioactive contamination includes half of the territory of this region, one third of the agricultural land and almost the same amount of the arable land. 9 districts, 734 towns and villages are located within the zone of radioactive contamination. In the long-term period after the disaster the situation in contaminated areas has improved and become predictable due to natural processes of recovery and implementation of countermeasures based on results of monitoring. However, until today regions of Ukrainian Polesia continue to produce agricultural products which do not meet the requirements of government regulations concerning the content of radionuclides in food and appear to present a threat to consumers. To assess the accumulation of 137Cs in plant products, we investigated the activity of these radionuclides in potatoes, vegetables, root crops and grains, and calculated the ratios of its transition from the ground to the products, which helped evaluate the intensity and amount of accumulation of radionuclides during the completion of the half-life period of 137Cs and evaluate the radiological situation in the northern regions of Polesia. The density of soil contamination with 137Cs and its specific activity in plant products grown on private plots were studied in three different districts of Zhytomyr region: Narodychi, Korosten and Ovruch. Analysis of the density of soil pollution with the 137Cs isotopes in the Northern part of Zhytomyr region in the post-disaster period shows that even 30 years after the tragedy, significant areas of arable land under certain conditions remain potentially dangerous on account of contaminated plant products. The specific activity of 137Cs in plant products grown on private plots was studied in residential places where soil contamination was detected. In particular, the list of studied crops included: potato tubers, white cabbage, fresh tomatoes, table beets, carrots, onions, beans, oat grains, corn grains. The most critical were populated areas located in zone II – village Vystupovychi of Ovruch district, village Loznytsia and village Khrystynivka of Narodychi district. In these settlements an excess of DR-2006 in plant products was noted despite the fact that an excess over the maximum permissible level of density of soil pollution was not observed. In decreasing order by the amount of CT 137Cs, we ranked crops as follows: beans > table beets > carrots > potato tubers > corn grains ˃ oats grains > white cabbage > onions > fresh tomatoes. For the population living on radioactively contaminated territories, plant products grown on private plots have been and still remain the main source of 137Cs radionuclides entering the body.
The study of the processes of restoration of species richness and productivity of steppe ecosystems after fires is an urgent problem that affects not only the conservation of biodiversity but also the maintenance of pasture resources. This article presents the results of a study of post-pyrogenic effects in steppe ecosystems, taking into account changes in the species composition of cyanoprokaryotes and algae that are art of the biological soil crust, which performs ecologically important functions in xerophytic ecosystems. The investigations were carried out in virgin and post-pyrogenic steppe ecosystems of the “Troitsk Clough” reserve (Zaporizhia region, Ukraine). For three years, the dynamics of the projective cover and the height of the vegetation cover in virgin areas of herbs-fescue-feather-grass and fescue-feather-grass steppes was studied as well as within two ecosystems of post-pyrogenic development after fires that occurred in the spring and winter periods. We discovered that restoration of the herbs-fescue-feather-grass and fescue-feather-grass steppes after fires occurs at different rates. The cause of the slow restoration of vegetation cover can be its severe damage by fire at the beginning of the vegetation season and the development of erosion processes. The number of species of cyanoprokaryotes and algae in the biological soil crust of virgin and post-pyrogenic ecosystems is not significantly different. It varies from 35 to 49 species. The greatest diversity is noted for Cyanoprokaryota. Chlorophyta is in the second place. Among the dominants, the filamentous forms of Cyanoprokaryota prevail. Nostoc edaphicum was noted as a nitrogen fixing representative. The similarity of the species lists of cyanoprokaryotes and algae of post-pyrogenic and virgin ecosystems, according to the calculated Jaccard coefficient, varies from 49.1% to 55.3%. This indicates a strong specificity of the composition of cyanoprokaryotes and algae in post-pyrogenic biological soil crusts. Changes in their composition reflect different stages of post-pyrogenic succession. In the first year after a fire, there is a slight increase in species richness, which is a consequence of the favorable effect of increasing the amount of mineral substances in the soil after the organic matter has burned out. The “pioneer” group includes: Phormidium autumnale, Ph. dimorphum, Ph. retzii, Ph. (Leptolyngbya) henningsii, Luticola mutica, Hantzschia amphioxys. Gradually this effect is leveled and the species richness of cyanoprokaryotes and algae is stabilized at a level peculiar for this type of ecosystem.
The article is focused on a hypothesis verification: the higher plants, microalgae and cyanobacteria may be used in bioindication of steppe ecosystem restoration dynamics after fires. On the territory of the Askania Nova biosphere reserve (Ukraine) 4 stationary polygons were investigated: SP1 – steppe area which had not been exposed to fire for 20 years preceding our study, as well as areas where single fires occurred in 2001 (SP2), 2005 (SP3), and a site where fires occurred in 2001 and 2004 (SP4). The investigation revealed the dynamics of height and projected area of the higher vegetation according to seasons during two years (2010 and 2011), as well as abundance and biomass of microalgae and cyanoprokaryotes in the soil layer by the layer of the depth to 15 cm. It was found that the effects of pyrogenic load remain evident for several years after the fires, manifesting in decrease of the height and projected area of herbage, the number and biomass of algae and cyanobacteria in the soil, especially to the depth of 5 cm. Multivariate general linear models were used to test the significance of the dependence of quantitative characteristics of vegetation, microalgae, and cyanoprokaryotes on environmental predictors (season, year, soil layer, and fire). In the model, 75.2% of the grass height variability and 91.6% of the grass projected area variability could be explained by the predictors under consideration. In the series SP1 → SP2 → SP3 → SP4 the grass height and projected area decreased. The differences in the projected area of the grass stand were most evident in spring. The model explained 89.1% of the variation in abundance and 91.6% of the variation in biomass of Bacillariophyceae. The abundance of Bacillariophyceae was greater in the upper soil layer than in the lower layer and decreased with depth. The abundance of this group of algae decreased in the series SP1 → SP2 → SP3 → SP4 at depths of 0–5 and 5–10 cm. Changes in abundances of Chlorophyta, Streptophyta, Heterokontophyta (Xanthophyceae and Eustigmatophyceae) equaling 47.6% could also be explained by the model. The abundance of this group of algae was greatest in the upper soil layer. In the upper soil layer, the maximum abundance of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was recorded for Polygon SP1 and the minimum for Polygon SP3. Within the model, 48.0% of the variation in biomass of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was explained by the environmental predictors. The biomass trend was coherent with the population trend. A special feature was that there was a significant increase in biomass at 10–15 cm depth at Polygon SP3 compared to other polygons at this depth. The model was able to explain 61.8% of the variation in abundance and 66.7% of the variation in cyanobacteria biomass. The highest abundance of cyanobacteria was found in the upper soil layer of polygon SP1. Somewhat lower numbers of cyanobacteria were at polygons SP2 and SP4, and the lowest were found in the upper soil layer at polygon SP3. In turn, the highest number of cyanobacteria was found particularly at this polygon in the 5–10 cm layer. The biomass in the 0–5 cm layer was coherent with the abundance pattern of this group. The research results confirmed that the quantitative characteristics of the higher vegetation (height and projected area) as well as of microalgae and cyanobacteria (abundance and biomass) may be used in bioindication of the dynamics of post-pyrogenic processes in steppe ecosystems.
Possibility of creation of effective algobacterial consortia with high nodulе ability of rhizobial cells is experimentally proven. Pre-sowing bakterization treatment of chickpea seeds provided the increase of the productivity of plants such polyfunctional cyanorhizobial complex by 43,4% in the conditions of the field experiment. It may serve as a base for biological technology of growing chickpea for obtaining of ecologically safe production. We brought under cultivation 12 strains associated with a strain of cyanobacteria Nostoc linckia 144, identified by their morphological, cultural, physiological, and biochemical properties. We revealed that on nitrogen-free substrate some 62 and 77% of strains satellite cyanobacteria and algae itself positively affect tuberization of soybeans and chickpeas and increase the dry weight of aboveground plant up to 28,6-35,7%; under condition of Southern black soils the bacterization of strains of Microbacterium laevaniformans KAGK and Mesorhizobium siceri raised the ground dry weight of plants per 0.82 g / plant (21.1%) compared with mono-farmery. We created the effective algological bacterial consortium of high activity of Mesorhizobium siceri cells, whose number was 9.7 h105 BUOD / mL, which exceed by two orders of magnitude higher the monoculture rhizobia. We proved experimentally the efficiency of usage of cyanobacteria combined with nodule bacteria in agrobiotechnology and suggested the high efficiency of prebacteryzation of seed by cyan-rhyzo-consortium of chickpeas which ensuring the increase of plant productivity by 43.4%.
