Evolution of diversity measures as a reflection of the process of primary soil formation in a model soil-plant system.

Abstract

We used information theory methods to analyze the process of primary soil formation in a model soil‐plant system with permanent cultivation of plants under controlled conditions. When studying the dynamics of the diversity of the microbiotic complex, the organic matter formed, and the distribution of macro- and microelements in plant organs, entropy of information source was used as their quantitative characteristic. We found that both production and expenditure of entropy simultaneously occurred in the model soil‐plant system. The integrity and interrelation of natural objects and phenomena underlie formation of the entire diversity of soils with their inherent information content [1]. When studying the information function of soils, informationtheory methods permit quantitative estimation of the relative diversity of structures of the multitude of elements and monitoring of changes of these structures with time. This approach seems to be very useful for analysis of the evolution of diversity measures in the case of physical modeling of primary soil formation reproduced in a model soil‐plant complex with permanent intense cultivation of plants in a regulated agroecosystem (RAES). In this study, we searched for certain quantitative relationships of the degree of diversity of the soil‐plant systems in a RAES and analyzed its effects on plant functions. It was established experimentally that considerable changes in physical, chemical, and biogenic characteristics of root-inhabited media (RMs) based on granite crushed stone and other mineral materials occur in the case of long-term year-round cultivation of plants (wheat and tomato) in RAESs. The element composition of plants, as well as the biochemical compositions of the organic matter formed in RMs and the accompanying microbiotic complex also changes [2, 3]. It has been noted that these changes in the RM‐plant system have much in common with the evolutionary processes involved in primary soil formation under natural conditions, with coarse mineral RMs being subjected to intense biogenic erosion in RAESs. Accumulation of the fine fraction, which readily interacts with elements of nutrient solutions and metabolites of soil microorganisms, is accompanied by formation of certain secondary minerals. The results of the studies performed may serve as a basis for physical modeling and mathematical simulation of the processes involved in primary soil formation in the RM‐plant system that occur for long periods of time under natural conditions and are drastically accelerated in RAESs. The purpose of this study was quantitative description of the response of the RM‐plant system to complex evolutionary processes occurring in it in the course of long-term cultivation of higher plants (23 vegetation cycles of wheat and tomato in a RAES) in a one-crop system for 11 vegetations, subsequent crop rotation, and the accompanying changes in the relative contents of micro- and macroelements in plant organs. These changes allow the researchers to obtain information on redistribution of chemical elements in plants and variation of diversity measures in the course of primary soil formation and the evolution of the RM‐plant system under controlled conditions. We studied the patterns of the relative redistribution and formation of the relative diversity of chemical elements (Ca, K, P, S, Na, Si, Al, Fe, Mg, and Cl) in the course of the evolution of the RM‐plant system that played an important role in mineral nutrition of plants. Simultaneously, we monitored the dynamics of the changes in the biochemical composition of formation of organic matter, including cellulose, hemicellulose, alkaline-soluble and alcohol‐benzene fractions, and nonhydrolyzed residue, as well as the amount of its water-soluble part in the nutrient solution. In addition, we analyzed the dynamics of the species composition and amount of microorganisms (bacteria consuming mineral nitrogen, bacteria consuming organic nitrogen, spore-forming bacteria, cellulose-fermenting bacteria, fungi, and actinomycetes) in RMs. The biogenic accumulation of chemical elements observed in this case is specific with respect to the mechanisms and results related to the initial stages of transformation of RMs into soil.