Thermodynamic exploration of the adaptive cycle

The adaptive cycle was proposed by Holling in 1985 to explain macroscale patterns and processes of ecosystem dynamics. According to this qualitative model, ecological succession progresses through four stages: 1) exploitation, 2) conservation, 3) collapse, and 4) renewal. Since introducing the adaptive cycle, many efforts have been made to improve, quantify, and expand the application of this model. In this paper, we developed a new thermodynamic model aligned with the four stages of the adaptive cycle. However, in contrast to the classic adaptive cycle, the present model provides a clear, quantified, thermodynamic definition of each stage by specifically considering the rates of entropy and energy production, consumption, and exportation. According to this model, steady state occurs when the entropy production rate and energy consumption rate of living organisms are balanced with the entropy exportation rate and gross primary production of the ecosystem. The growth-oriented exploitation stage (1) requires a positive energy balance and a negative entropy balance. When both energy and entropy balances are negative, the ecosystem enters the conservation phase. If the energy balance is negative and the entropy balance is positive, then the system will collapse (3). Finally, when both entropy and energy balance are positive, new subsystems will emerge and adapt to continue a path of exploration and a new cycle of succession (4). Since this work is based on pure theoretical thermodynamics, these four stages of growth and development may apply to any complex adaptive system.