Sukachev considered studies of biogeocoenoses as an independent science - biogeocoenology, which studies the biogeocoenotic process. The idea of the biogeocoe-notic process proper, being formed after the definition of the notion 'biogeocoenosis', is the content of the concept and supplements the Vernadskii ideas for the local level of the biosphere organization. In addition, the elaboration of the concept of biogeocoenotic process was based on the ideas of materialistic dialectics (in this aspect, Sukachev was close to Tansley), kibernetics, and systems theory affecting greatly the development of science in the 1960s. The abundant experience of Sukachev himself as a paleobotanist, geobotanist, geographer, and naturalist was also of great importance.
The dialectic law of the unity and conflict of opposites is postulated as the basis of self-development of biogeo-coenosis, with its existing discontinuities or disruptions, destruction of the old, and initiation of the new. Although a biogeocoenosis is an open system, all of its components together still form a certain integral dialectical unity characterized by internal contradictory interactions, which never produce a state of equilibrium within that unity (system). Climatope, edaphotope, phytocoenosis, zoocoenosis, and microbocoenosis are considered as components of biogeocoenoses.
The action of these interior forces leads to self-development, whereas the effect of the external ones leads to some variation and disturbance of the developmental process proper. It is practically useful to consider the mechanisms of nonequilibrium thermodynamics discussed by I. Prigogene, and the dynamics of nonlinear dissipative systems with positive and negative feedbacks capable of innovations discussed by G. Hacken.
The biogeocoenotic process is understood as a change in the matter and energy exchange due to the interaction of organisms with each other and with the environment, as well as between components of biogeocoenosis. The biogeocoenotic process includes not only interactions and exchange of matter and energy between biogeocoenose components, but also interactions and exchange of matter and energy between biogeocoenoses and their surroundings - the environment, in which they exist, and other biogeocoenoses (both adjacent and more remote ones). Since the process of interaction of a biogeocoenosis with its environment is partly expressed in terms of the incessant outflow of energy into space, it has, as it were, an entropic character. But, at the same time, new matter and energy are constantly entering the biogeocoenosis. A bio-geocoenosis is considered as an elementary cell, and the biogeocoenotic process in each biogeocoenosis is typical due to specific relations between the biogeocoenosis components and the interaction with their environment. Under similar environmental conditions, biogeocoenoses with similar composition and structure also realize similar biogeocoenotic processes. Evidently, this model is the basis for the development of spatial hierarchical organization of biogeocoenosis, and the author of the concept suggests that the biogeocoenotic cover is a set of interacting biogeocoenoses over a rather vast territory.
The biogeocoenotic process unites four relatively independent processes:
1. The interactions of biogeocoenosis components and elements among themselves, which do not remain constant, but change in time and alter the course of the biogeocoenotic process. This process is a purely internal one and may be called 'endocoaction'.
2. The introduction of microorganism germs, plants or new species of organisms by wind and water, and of some organisms from outside, which can change somewhat the biogeocoenotic process. This process was proposed to be called 'inspermation'.
3. The introduction of mineral and partly organic matter with dust, surface, and intrasoil runoff. This process is called 'inpulverization'.
4. The removal of mineral and organic matter by water and other organisms. This process is called 'expulverization'.
The process of internal interactions never ceases; it slows down or accelerates to some extent. The slowing down is determined by a gradual increase in the resilience of biogeocoenosis, but the acceleration is determined by the disturbance of this stability via both settling of new species and changes in the structure of the interactions in the course of self-development. The second and third processes change at the level of the biogeocoenotic cover resulting from climatic and geodynamic fluctuations and asynchronous self-development of neighboring biogeocoenoses as well. The fourth process may be considered as an irreversible one to a considerable degree, and if it is not compensated for the third process, the changes in biogeocoenosis are determined by slow but permanent removal of mineral and organic substances from it. Finally, within the biogeocoenotic cover, the process of formation related to the origin of new phenotypes, genotypes, and morphofunctional forms of organisms is also realized.
A rather strict definition of the biogeocoenotic process as a change of states determined by different mechanisms allowed Sukachev to construct a harmonious classification of the dynamics of biogeocoenoses and biogeocoenotic cover on the following basis: equilibrium process with natural reversibility; nonequilibrium irreversible process; self-development (autogenous or endogenous processes), processes under the influence of external forces (exogenous); according to variation in time and space.
The classification of types of dynamics of the forest biogeocoenoses elaborated by Sukachev is given below:
A. Cyclic (periodic) dynamics of forest biogeocoenoses
(reversible changes in forest biogeocoenoses).
(1) Daily changes in biocoenoses.
(2) Seasonal changes in biocoenoses.
(3) Annual (weather) changes in biocoenoses.
(4) Changes in biocoenoses due to the process ofregen-eration and growth of woody and other vegetation:
(a) regular regeneration of woody plants;
(b) irregular (wave) regeneration of tree stands;
(c) synusial dynamics, especially parcel dynamics (these variants of the dynamics were likely to be associated with a gap dynamics model; models of these types of relationships reproduce usually restricted quasi-cyclic fluctuations of productivity, biomass, and species composition).
B. Dynamics of the forest biogeocoenotic cover of the earth, or successions of forest biogeocoenoses.
I. Autogenous (irreversible) successions of biogeocoe-
noses (developments of the forest phytogeosphere, of forest biogeocoenogenesis).
(1) Syngenetic succession of biogeocoenoses.
(2) Endogenous (endodynamic) successions of biogeocoenoses.
(3) Phylocoenogenetic successions of biogeo-coenoses:
(a) phytophylocoenogenetic successions of bio-geocoenoses;
(b) zoophylocoenogenetic successions of bio-geocoenoses.
(Note. Syngenetic processes are irreversible ones that proceed only due to alterations in the species structure without irreversible environmental changes (typical processes are the development of high bogs, progressive development of eluvial and illuvial horizons of soils). Phylogenetic successions imply processes determined by the origin of new forms. Probably, such processes are useful to be included into the dynamics determined by phylocoenogenesis of viruses and bacteria, including also the saprophytic microorganisms).
II. Exogenous (reversible and irreversible) successions of biogeocoenoses.
1. Hologenetic (irreversible) successions of biogeocoenoses:
(1) climatogenic successions of biogeocoenoses;
(2) geomorphogenic successions of biogeo-coenoses;
(3) selectocoenogenetic or areogenic successions of biogeocoenoses;
(a) phytoareogenic successions of biogeocoenoses;
(b) zooareogenic successions of biogeocoe-noses.
(Note. Hologenetic processes are realizable at the regional level of the biogeocoenotic cover organization. It is worth noting that Sukachev did not extend the principle of actualism and reversibility to climato-genic, that is, paleoclimatic successions. Selectocoenogenetic successions may appear due to the invasions of alien species. Changes determined by invasions of agents of feral herd diseases of plants, animals, and saprophytic microorganisms are expedient to be included into this type of dynamics. A typical example is the mass and, most likely, irreversible death of American chestnut (Castanea dentata (Marsh.) Borkh.) in the Appalachians. If species change their properties in the process of settling, selectocoenogenetic successions are indistinguishable from phylocoenogenetic ones).
2. Local (reversible and irreversible) catastrophic successions of biogeocoenoses.
(a) anthropogenic successions of biogeocoenoses;
(b) zoogenic successions of biogeocoenoses;
(c) pyrogenic successions of biogeocoenoses;
(d) windfall successions of biogeocoenoses;
(e) successions of biogeocoenoses produced by mud streams, landslides, sudden inundations, and other causes.
Probably, this classification of the dynamics may be recognized as the most complete. For the modern ecology, it contains all the bases for particular and integrating models of dynamics and research programs (e.g., programs directed to the accumulation of data on the irreversibility of self-development processes). However, in order that the concept of biogeocoenosis might create the necessary bases for studies and simulation of biogeochemical cycles, it should contain some concrete system definition and refinement of ideas of the spatial-temporal hierarchy and elimination or weakening of contradictions between individualistic and organism concepts of spatial organization of the biosphere and its components.
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