[Evaluation of seasonal dynamics of crop yield in agrocenoses on the basis of satellite data and mathematical model].

An integrated approach based on satellite remote sensing data and the results of mathematical model analysis was tested for applicability in evaluating the crop yield and total of phytomass of agrocenosis and identifying its type. The dynamics of the normalized difference vegetation index (NDVI) and the total aboveground phytomass of agrocenosis proved to be qualitatively similar. An analysis performed using the mathematical model and taking into account air temperature showed the possibility of making and refining prognosis of crop yield. In this course, the vegetative and generative parts of the agrocenosis were distinguished, and it was found that the model data matched the ground survey data under optimal environmental conditions.

[Dynamics of seasonal plant growth in halophytic meadows taking into account the temperature factor and soil salinity level].

A mathematical model has been constructed to describe the growth dynamics of various plant communities of halophytic meadows depending on the temperature factor and degree of soil salinity. Field investigation of the yields of halophytic meadow plant communities were performed in the coastal area of Kurinka Lake in the Altaiskii district of the Republic of Khakasia in 2004 and 2006. The results of field investigations and model studies show that there is a correlation between plant growth and air temperature for plant communities growing on soils with the lowest and medium salinity levels. It was proven in model studies that for the plant communities that grow on highly saline (3.58%) soils, not only air temperature but also the salinity level of the soil should be taken into account.

[An experimental study and a mathematical model of interactions in mixed culture of invertebrates and algae in the "producer-consumer" aquatic biotic cycle]. / Eksperimental'noe issledovanie i matematicheskaia model' vzaimodeistviia smeshannoi kul'tury bespozvonochnykh i vodoroslei v vodnom bioticheskom tsikle (produtsent-konsument).

An experimental investigation was carried out, and a mathematical model of interaction between invertebrates (infusoria Paramecium caudatum and rotifera Brachionus plicatilis) and algae (Chlorella vulgaris and Scenedesmus quadricauda) in the "producer-consumer" aquatic biotic cycle with spatially divided links was constructed. The model describes the dynamics of a mixed culture of infusoria and rotifera in the "consumer" link, when they consume a mixed culture of algae coming from the "producer" link. A negative influence of products of algae Scenedesmus metabolism upon the reproduction of infusoria P. caudatum was revealed. Taking this into account, a qualitative coincidence of the results of mathematical modeling with experimental data was obtained. It was shown that the co-existence of mixed algae culture in the "producer" link with invertebrates in the "consumer" link in the "producer-consumer" aquatic biotic cycle is impossible because of the displacement of infusoria P. caudatum by rotifera Brachionus plicatilis.

[Mathematical model of the interaction of components in a plant-rhizospheric microorganisms system at the higher level of carbon dioxide in atmosphere]. / Matematicheskaia model' vzaimodeistviia v sisteme rastenie-rizosfernye mikroorganizmy pri povyshennom soderzhanii dioksida ugleroda v atmosfere.

A mathematical model describing the interaction of plants and rhizospheric microorganisms on complete mineral medium at a higher CO2 level in the atmosphere was constructed. The positive effect of CO2-enrichment on the system plant--rhizospheric microorganisms was shown. The effect of rhizospheric microorganisms on plant growth at normal and high level of carbon dioxide was demonstrated. It was shown that the biomass of plant in the system is smaller than the biomass of plant growing without microorganisms. It was experimentally demonstrated that a simple ecosystem wheat--Pseudomonas putida--artificial soil develops and functions differently than its individual constituents in the case of a wheat-artificial soil system. With unlimited nutrition and a higher CO2 level (0.06%), plants with roots inoculated with microorganisms have a smaller biomass than plants that were not inoculated with microorganisms.

Experimental models of small closed systems with spatially separated unicellular organism-based components.

Experimental models of small biotic cycles of different degree of closure and complexity with spatially separated components based on unicellular organisms have been studied. Gas closure of components looped into "autotroph-heterotroph" (chlorella-yeast) system doubled the lifetime of the system (as opposed to individually cultivated components). Higher complexity of the heterotroph component consisting of two yeast species also increased the lifetime of the system through more complete utilization of the substrate by competing yeast species. The lifetime of gas and substrate closed "producer-consumer" trophic chain (chlorella-paramecia) increased to 7 months. In 60 days the components' numbers reached their steady state followed by more than 40 cycles of the medium. The role of a predator organism (protozoan) in nitrogen cycling was demonstrated; reproduction of protozoa correlated directly with their emission of nitrogen in the ammonia form that is most optimum for growth of chlorella.

[Interaction in the phage-bacterium system]. / Issledovanie vzaimodeistviia v sistema fag-bakteriia.

The growth rate of the phage for Brevibacterium was studied as a function of the population of the host bacterium and its growth rate. The interaction was not additive when the phage-bacterium system was modeled in chemostat and in periodic regime. This fact was taken into account to describe more precisely and completely the qualitative characteristics of such a system as compared to models of the predator-victim type.