A model of mass and energy flow in ecosystems

Abstract Ulanowicz and May propose a global closed ecosystem model from the viewpoint of mass and energy flow. They show a necessary and sufficient (or sufficient) condition for ecosystem stability, and explain a certain rule which is derived from field data. But their papers both contain a physical mistake: Mass does not circulate in the correct direction under the stability condition. In this paper two modifications of Ulanowicz and May's models, in which the mistake is eliminated, are proposed to explain the rule, and a necessary and sufficient stability condition is shown.