Nº 4 (2024)

We tested the hypothesis that the number of seedlings from the soil seed bank (SSB) in forests polluted by heavy metals and disturbed by recent fires decreases. It was also assumed that the consequences of pollution and fires for the soil seed bank are additive. We estimated the number of seedlings from the SSB of pine forests located near the Karabash copper smelter (KCS) (contaminated by Cu, Zn, Pb, and Cd) and from uncontaminated forests of the Ilmen State Reserve (ISR). In both areas, samples of the forest litter and humus horizon were taken from forests recently exposed to ground fires and long-term unburned forests. Samples were exhibited from June to September, conducting seven rounds of counting seedlings. Small peculiarities of the emergence of seedlings on the samples of the forest litter and the humus horizon were established. However, the regularities of the reaction of SSB to pollution and fire disturbances did not depend on the soil horizon. The number of seedlings on substrates from contaminated forests was 5–8 times lower than the number of seedlings on substrates from background forests. A decrease in the number of seedlings on polluted substrates was accompanied by an increase in the share of dicots in the total number of seedlings. The relationship between the number of seedlings and the age of fires was not found. The additivity of the consequences of pollution and fires has also not been established. Of the two types of damage, pollution and fires, the pollution factor is of leading importance for SSBs. The results indicate a low recovery capacity of the herb-shrub layer of polluted forests.

On 12 sample plots established in the ecotone of the northern forest boundary in the Khadyta-Yakha River valley on the Yamal Peninsula, time of emergence and death, as well as productivity of about 1000 Siberian larch (Larix sibirica Ledeb.) and Siberian spruce (Picea obovata Ledeb.) trees were analyzed. Over the last 140 years, there has been a sharp increase in the stocks and annual growth of stem phytomass of woody plants within the studied ecotone. Since the 1970s, the average annual growth of phytomass has been increased by 1.2–39 times, which was facilitated by a 0.9^оC increase in average June–July air temperature. However, this effect is insignificant in areas of mixed open forests subjected to periodic logging.

Overall, 34 local floras of vascular plants were analyzed at testing sites in the Middle Volga region with an area of 400 km². Noticeable differences were revealed in the nature of correlations between the number of species of adventitious and native flora fractions and environmental factors: climate and relief. In the region, the number of native species is negatively related to air temperature, evaporation rates, and water deficit, while adventive species show a positive relationship with these characteristics. Adventive species are more often found in gently sloping lowlands in polygons characterized by increased elevation differences and drainage area. In general, adventitious species are more associated with semi-arid conditions in sites with relatively high ranges of environmental factors and standard deviation. Multiple regression showed that adventive species are more closely related to environmental factors than native species. In the region, adventive species are distributed predominantly in places (ecotopes) with increased environmental heterogeneity. An analysis of the relationships with environmental factors of the studied fractions may indicate that their distribution on the test sites is consistent, as a result of which they do not show opposition, which is also confirmed by the weak positive relationship between the richness of their species.

The distribution of trematodes Paracoenogonimus ovatus and its first intermediate hosts, viviparous Viviparus viviparus and V. contectus in the Ob–Irtysh basin were analyzed. Until the 1990s the spreading of P. ovatus in this region was associated with habitats of V. contectus, which is considered a native species in Western Siberia. Since the mid-1990s European species V. viviparus began to spread in the Ob basin. Before this, only one source of infection with P. ovatus was known associated with finding V. viviparus in the Lower Irtysh. This paper describes another such outbreak in the Tura River near the city of Tyumen. In fish from the Tura River, a generally high extent and intensity of invasion were noted. Further expansion of the range is predicted P. ovatus associated with expansion V. viviparus.