System-analytical modelling—Part II: Wheat biotime run and yield formation. Agroclimatic potential, the Le Chatelier principle, and changes in agroclimatic potential and climate in Russia and the U.S.

System-analytical modelling (SAM) shows that plants possess two types of biological time that alternate during the annual cycle of plant development. The alternation of these biotimes and the process of yield formation are described by the previously derived information principle. The elaborated model of the agroecosystems of wheat is characterized by theoretically best accuracy. The model serves as a basis for the universal model of land agroclimatic potential (AP). This study simultaneously estimated the vegetation biotime run and phenological development, 12-month dynamics of soil humidity, yield formation and its bulk, multiple year trends of mean monthly air temperature, monthly precipitation, and agricultural technologies efficiency dependent on soil fertility as well as AP dynamics. The calculations were made through the mathematical solutions of inverse problems, with the help of the model. Only the long-term series of actual wheat/cereal yields, along with the long-term average monthly values of air temperature and precipitation, were used as input data. With SAM and the grain-producing area of Siberia as a case study, the information basis for the well-known Le Chatelier principle characterizing self-stabilization of ecosystems and agroecosystems has been revealed. Self-stabilization provides the restriction on random variations of their specific basic processes (informational regulated biomass formation) up to 24%. Under such a restriction, the transfer of stochastic information that destroys the system information stability does not exist. SAM of current changes in both AP and climate in grain-producing areas of Russia, as well as in the U.S., has shown that the AP of the U.S. is twice as much as the Russian one. The manifestation of global warming in the U.S. is more significant than in Russia, and a decrease in precipitation in the U.S. and an increase in precipitation in Russia were found.