Ecosystem Configurations Consequent on the Maximum Respiration Hypothesis

The Maximum Respiration Hypothesis (MRH) asserts that matured ecosystems organize their configuration to maximize community respiration. Hence the object of the hypothesis is not individual living organisms but the whole ecosystem. In this paper we use two types of ecosystem models to show how the MRH works in ecosystems. The first is a simple theoretical model that consists of two compartments: a producer and a decomposer. The main results of this first model are as follows. (1) The model presents the community structure which is consistent with the MRH. (2) The dual solution (respiration values) presents the scarcities of different types of matter and energy in an ecosystem with maximal respiration. They operate as similar indicators to the inverse of buffer capacity. (3) The model, when extended to include two types of decomposers, can show the conditions of the coexistence and the competitive exclusion of components. Even if two biological components are strongly overlapping in their ecological niches, a slight differentiation of the ratio of matter exchanges can permit the coexistence. The competition and the coexistence are regulated by the imperative shown by the MRH. The second model is a simulation model for a hypothetical grassland ecosystem which consists of 19 biological components, and 15 kinds of matter and energy. The model includes a grazer system and a decomposer system. The main results are as follows. (1) The ecosystem configuration for biomass production, consumption, egestion, nutrient production, and respiration is presented under the MRH. It especially shows the dominance of the decomposer system. (2) Interspecific substitution guided by respiration values cause an increase in community respiration. If an inferior component undergoes a mutation to increase its production of net respiration value, the component may dominate its competitor and contribute to the increase in the community respiration. This means that the MRH can predict the working of natural selection from the macroscopic point of view.