Abstracts

Evolution of Species and Ecosystems: Theoretical Analysis and Computer-Assisted Modeling

The principal difficulty involved in describing and studying biologic diversity lies in its more or less pronounced spatial structurization and strong heterogeneity. This is most clearly pronounced in phytocenoses, since the majority of plant species as a rule fill their habitats rather nonuniformly to form accumulations and voids that can far from always be convincingly explained by heterogeneity of the environment in the respective ranges. An impressive example here is clearly pronounced spottiness of tundra phytocenoses; yet, taiga plant communities, too, prove to be very spotty and heterogeneous as well. A successful description and analysis of the mechanisms of this heterogeneity within the framework of classic biological investigation methods are still pending. This communication suggests a mathematical model for spatial-temporal dynamics of plant communities to explain the arisal of heterogeneous (spotty) spatial distribution by instability of community dynamics by phenomena of dynamic chaos and processes of chaotic self-adjustment. In plotting the given model, we accounted for interaction of plants situated close to each other and affecting both increase of biomass (new shoots, for instance) and restricted biomass growth caused by competition for resources needed for vital activity (primarily involving light). The basic model version is as follows:

,

where img src="http://www.bionet.nsc.ru/meeting/bdne2001/images/report/frisman02.gif" > is the biomass density of the i-th species in point x in time t, M the physical space, the community habitat range; parameter γ characterizes the sensitivity of suppressed biomass to competitive impact, parameter ρ reflects the non-linearity of dependence of degree of competitive limitation on the density of the overwhelming biomass, and kernels and characterize the growth and dissimilation of the biomass; they depend on the distance between points x and y, and may be selected in the form of Gaussian curves. It was shown that increase in intensity of competitive pressure leads to chaotic self-adjustment and rise of complexly structured heterogeneous (spotty) spatial distributions.

Simulation results are illustrated by spottiness structure analysis (groups of trees with overlapping crowns) in experimental site of reserve taiga in the north of Khabarovsk Territory. An attempt was made to forecast succession of forest types.

Note. Abstracts are published in author's edition

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