Estimation of the thermal and photochemical stabilities of pheromones.

The correlation between the kinetic stability of molecules against temperature and variations in their geometric structure under optical excitation is investigated by the example of different organic pheromone molecules sensitive to temperature or ultraviolet radiation using the density functional theory. The kinetic stability is determined by the previously developed method based on the calculation of the probability of extension of any structural bond by a value exceeding the limit value Lмах corresponding to the breaking of the bond under temperature excitation. The kinetic stability calculation only requires the eigenfrequencies and vibrational mode vectors in the molecule ground state to be calculated, without determining the transition states. The weakest bonds in molecules determined by the kinetic stability method are compared with the bond length variations in molecules in the excited state upon absorption of light by a molecule. Good agreement between the results obtained is demonstrated and the difference between them is discussed. The universality of formulations within both approaches used to estimate the stability of different pheromone molecules containing strained cycles and conjugated, double, and single bonds allows these approaches to be applied for studying other molecules. Graphical Abstract Estimation of the thermal and photochemical stabilities of pheromones.

[Altitude-belt zonality of wood vegetation within mountainous regions of the Sayan Mountains: a model of ecological second-order phase transitions ].

As a description of altitude-belt zonality of wood vegetation, a model of ecological second-order transitions is proposed. Objects of the study have been chosen to be forest cenoses of the northern slope of Kulumyss Ridge (the Sayan Mauntains), while the results are comprised by the altitude profiles of wood vegetation. An ecological phase transition can be considered as the transition of cenoses at different altitudes from the state of presence of certain tree species within the studied territory to the state of their absence. By analogy with the physical model of second-order, phase transitions the order parameter is introduced (i.e., the area portion occupied by a single tree species at the certain altitude) as well as the control variable (i.e., the altitude of the wood vegetation belt). As the formal relation between them, an analog of the Landau's equation for phase transitions in physical systems is obtained. It is shown that the model is in a good accordance with the empirical data. Thus, the model can be used for estimation of upper and lower boundaries of altitude belts for individual tree species (like birch, aspen, Siberian fir, Siberian pine) as well as the breadth of their ecological niches with regard to altitude. The model includes also the parameters that describe numerically the interactions between different species of wood vegetation. The approach versatility allows to simplify description and modeling of wood vegetation altitude zonality, and enables assessment of vegetation cenoses response to climatic changes.

[Stability of lepidopterous pheromone molecules of forest insects to environmental factors].

The interactions of the pheromones of some representatives of the Lepidoptera order with each other and with materials contained in the forest air, as well as the effect of electromagnetic radiation on pheromone have been studied. It was found that the reactions of pheromones with substances contained in the forest air are irreversible and proceed with the liberation of heat. Electromagnetic radiation affects very strongly the structure of pheromones. In this case, a pheromone molecule is activated and can readily enter into reaction.

[Succession in forest coenoses: a model of second-order phase transition].

The changes of arboreous coenoses composition resulting from natural and anthropogenic impacts are considered. The mathematical model is proposed and verified that describes arboreous cenoses transition from one succession state into another by analogy with phase transition in statistical physics. It is demonstrated that the model is concordant with the data of full-scale observations. The model allows to explain the trend of succession processes and determine the stage of forestation process at which succession transitions should be expected. The analysis of full-scale observations data by means of the proposed approach makes it possible to calculate, for given regions and forest types, the critical values of planting phytomass that, upon being attained, initiate the succession transition. Those values are important to be known for middle- and long-term forecasting of forest cover dynamics.

[Phenomenological models of the forest plantations growth].

Phenomenological models of the forest plantations growth are analyzed. Those derived from the Verhulst's model are shown to fail describing qualitative effects reflecting tree growth, phytomass withdrawals, and plantation restoration. The method of phase portraits is used for exploration of the forest ecosystem dynamics, which allows to describe regulatory mechanisms of the growth processes, regulation delay, and feedback types. A bistable phenomenological model is suggested herewith to characterize dynamic processes in the forest ecosystems. Principal patterns of formation of the forest plantations at different stages of the forest generation processes are considered on the basis of that model, and ecological effects responsible for the plantation dynamics are revealed.

[A population and energetic model of an outbreak of forest insects].

A model of the population dynamics of insects has been developed, which takes into account the food consumption by insects and the reaction of food plants to the damage. Equations have been derived that describe the relationship between the coefficient of insect reproduction, the weight of females, the energetic effectiveness of the food consumption by insects, and the reaction of food plants. The scenarios of population outbreaks have been analyzed as a function of the weight of females in the stable state. The results of modeling have been compared with the data of natural observations.

[Oxidoreductase activity of peat soils as an indicator of the degree of biochemical transformation of drained and forested bogs in west Siberia].

Multivariate analysis unambiguously demonstrated the differentiation of oxidoreductase activity (catalase, peroxidase, and dehydrogenase) in peat soils after a 20-25-year period of bog drainage and afforestation. The enzyme activity depended on the drainage depth. A statistical model has been developed to predict the degree of humification of peat organic matter from peroxidase activity and moisture of drained soils. Soil peroxidase activity can be an important indicator of the degree of biochemical transformation of drained and forested bogs.