Ecology

Enchytraeid communities were studied in the upper soil of birch forests in areas within the pollution gradient of emissions from the Middle Ural Copper Smelter. In the unpolluted area, 17 species were identified (6 to 13 in different sample plots); the average density was 13 666- 44 903 ind./m², and the average (raw) biomass was 1 357- 3 699 mg/m². Near the smelter, the population density, biomass, and species richness were reduced by 80, 20, and 2.4 times, respectively. However, the communities structure of diversity changed insignificantly, and the diversity of enchytraeids in the impact zone is potentially comparable to the one of the background zone. In the background zone, the highest density and biomass values were concentrated in the upper layer (0- 2 cm) of the soil, corresponding to the forest litter (61 and 63%, respectively). In the impact zone, the vertical distribution of enchytraeids was different: density (59%) and biomass (61%) were redistributed to the underlying (2.1- 4 cm) layer (corresponding to bottom layer of the litter) containing the highest concentrations of metals. Changes in vertical distribution of enchytraeids are not expected to be related to pollution effects.

The geographic distribution and hybridization patterns of six roburoid oak species growing in the Western Caucasus, as well as the ecological association of the species and their hybrids were studied using 18 nuclear microsatellite loci. The wide distribution of limestone oak Q. calcarea Troitsky, a species genetically and ecologically distinct from sessile oak Q. petraea and downy oak Q. pubescens, was confirmed in the studied region. Five species were found in a genetically pure form (Q. robur, Q. hartwissiana, Q. petraea, Q. calcarea, and Q. pubescens). Using the Bayesian clustering method, their individuals are grouped into separate clusters according to their taxonomic affiliation. These species grow sympatrically in the Western Caucasus, occupying different ecological niches. The morphological features that distinguish pure individuals are stable and consistent with the genetic data. Hybridization is observed in all species, but the number of hybrids between species varies significantly. The largest number of hybrids is formed between the short-pen-duncle oaks Q. pubescens, Q. calcarea and Q. petraea. According to the degree of hybridization, two zones are clearly distinguished in the Western Caucasus: the area of distribution of Q. pubescens, where hybrids accounted for more than half of the composition in all populations (64.3% in mean), and the area outside the range of Q. pubescens, where the proportion of hybrid samples was significantly lower (10.6%). In all populations involving Q. pubescens in the extreme west of the Caucasus, a high level of introgression is revealed between Q. pubescens and Q. calcarea, with a predominance of hybrid samples over pure individuals, with a continuum of transitional morphological forms. Significant heterogeneity is observed in the composition of species and hybrids depending on the location of the sampling points and habitat conditions. The proportion of the Q. pubescens cluster, identified using the Bayesian clustering STRUCTURE, is highest in the driest habitats near the seashore and decreases with distance from the sea and in more humid ecotopes, reflecting different ecological properties of Q. pubescens and Q. calcarea, as well as ecological properties of hybrids, depending on the contribution of genes of the parental species. The high-mountain species Q. macranthera, extremely rare in the Western Caucasus, was not observed in the studied populations in pure form, but was found in hybrids.

This study analyzes for the first time the climate signal in the radial growth of Scots pine and Siberian spruce growing in the territory of the Udmurt Republic. In some years, synchronous, sharp changes in radial growth were observed in the studied chronologies. This applies to both minimum and maximum values. An assessment of the influence of average monthly air temperatures and precipitation amounts for the current and previous years revealed differences in the response of pine and spruce radial growth to climate. Spruce radial growth is most influenced by the previous year's growth, as well as hydrothermal conditions at the beginning of the growing season. Pine radial growth is largely influenced by the temperature regime in the spring months preceding the onset of the growing season. Observed climate change has led to a weakening of the correlation between the growth of both species and both temperatures and precipitation amounts in the summer months in recent decades. This indicates that conditions have become more favorable for tree growth. Conversely, the correlation with climatic conditions in the pre-vegetation period has increased. Thus, continued increases in winter and spring temperatures and precipitation are expected to promote radial growth in both species.