Vol 9, No 7 (2016)

A model that implies highly inertial regulation of phytophage numbers by entomophages has been applied for the analysis of phytophage–entomophage interactions during different phases of the gradation cycle of phyllophagous insects. The data on population dynamics and the degree of parasite infestation in pupae of the pine looper Bupalus piniarius L. and fir looper Ectropis (=Boarmia) bistortata Gz are used to verify the model. The results of field studies apparently are in good agreement with the model of highly inertial regulation in the “phytophage–entomophage” system. The model that is proposed explains the decisive roles of different factors (entomophages, predators, or diseases) in the population dynamics of phytophages under different conditions.

Coenotic features of boreal, nemoral, and subnemoral spruce stands of the southwestern part of Moscow region have been studied using ground-based and remote sensing data. Despite significant modifications of the vegetation cover in the region due to human impacts, the species composition of the spruce communities still retains typical zonal features of the regional vegetation and is associated with certain landscape elements. Cartographic modeling has allowed us to identify the spatial distribution patterns for various spruce forest types and produce a series of geobotanical maps (scale 1: 100000). The ecophytocoenotic approach was used for classifying the forest vegetation. An analysis of the spatial differentiation of the forest cover—using spruce forests with different species composition as an example—has confirmed the ecotonal structure of the study area demonstrated through a characteristic latitudinal distribution of geoecolological spectra of species.

The relationships between the health of Pinus sylvestris trees and stands and the levels of anthropogenic stress and fragmentation of habitats have been studied based on the example of pine stands of natural origin in Yekaterinburg and its vicinity (48 sampling plots located at different distances from the center of the city). The distances from the city center and from the boundary of a built-up area to a sampling plot and the population density around this plot are taken to characterize the level of anthropogenic stress. The area and perimeter of a forest site; the distance from the boundary of a sampling plot to the forest edges; and the shape of forest edges are used to characterize the level of fragmentation of habitats. We have found that the average morphological metrics of trees have slight changes, while the traits of tree health are significantly altered under urban environment. The overall performance of stands decreases by 22–35% in the urbanization gradient. The health of stands is most substantially influenced by the forest-site area. The population density around sampling plots and the distance of these plots from the megalopolis center have a lower effect on the health of trees and stands. Fragmentation of forests in the city leads to a decrease in the size of forest sites, which causes a decrease in wood stocks and the diameter and height of trees and the deterioration of their health. The lowest area of the forest to make it sustain an urban environment is about 30 ha. The untransformed core of forest is located no less than 70 m from the forest edge.

The population structure of common juniper (Juniperus communis L.) growing in the Cis-Urals and Southern Urals has been studied using 17 morphological traits of generative and vegetative organs. A multivariate analysis of ten coenopopulations has recognized three phenotypically different local populations: Cis-Ural, forest Cis-Ural forest-steppe, and Southern Ural mountain populations. The Cis-Ural forest population is strictly associated with lowland pine forests of the northwestern part of the Bashkir Cis-Urals. The Cis-Ural forest-steppe population is located in the northwestern part of the Bashkir Cis-Urals and the southeastern part of the Udmurt Cis-Urals. The Southern Ural mountain population is located in the central part of the Southern Urals and is associated mainly with mountain pine and dark coniferous forests. The last population is divided into forest and forest-edge subpopulations; the first one is represented by typical undergrowth locations, whereas the second is associated with open steppelike slopes and forest edges. In general, based on morphological traits of generative organs, the revealed local subpopulations hold an intermediate position between the Eastern European and Siberian populations of common juniper. Based on the morphological traits of vegetative organs, Cis-Ural populations are considered related to the populations of the European part of Russia, whereas the mountain Southern Ural population resemble Siberian populations. Concerning morphological traits of generative organs, the intrapopulation phenotypic diversity of common juniper is higher for mountain habitats; in the case of vegetative organs, the maximum diversity is observed for lowland habitats. The character of phenotypic differentiation determines the need to conserve the gene pool of common juniper of the Cis-Urals and southern Urals on a population basis.

We have studied the natural regeneration of spruce (Picea abies L.) under a canopy of pine (Pinus sylvestris L.) on loamy soils. Spruce survival and growth depend on the duration of the regeneration period from the creation of the plantation and the local conditions formed as a result of uneven thinning of pine and spruce canopy. The formation of spruce population is mainly determined by trees that regenerated upon intensive thinning of 20- to 40-year-old pine trees. Spruce regeneration may be enhanced by timely cleaning cutting in pine plantations. The first one, done at the age of 15–20 years, favors pine growth and spruce regeneration. At the normal reproduction of spruce population under the canopy of 80-year-old pine plantations, the second spruce layer is formed. Trunk reserve in this layer is 20–25% of the reserves of the first layer. After its formation, the light regime in the forest depends greatly on the space volume occupied by spruce crowns. Their percentage is especially high at the relative height equal to 0.4–0.7 of the mean spruce height in the second layer. Smaller spruce trees may exist for a long time period, but their development is slowed down and they die at the undergrowth stage. When the plantation is 150 years old, the reserves of spruce trees regenerated under the canopy of pine comprise one-third of the total reserves of the plantation. If the growing conditions are favorable for spruce (C₃), the stability and productivity of pine-spruce plantations exceed those of the pure spruce plantations. The reasonability of natural spruce regeneration for the creation of pine-spruce plantations under C₃ conditions should be substantiated with the consideration of their designation, ages of cuttings, and the possibility of plantation creation and sanitary cuttings according to the valid regulations.