Acclimation in dynamic models based on structural relationships

1. A number of recent tree growth models have been based on the assumption that tree structure follows certain empirical rules and carbon allocation i s performed so as to maintain these rules when growth and senescence occur simultaneously. This paper introduces a method of combining structural rule s with adaptive regulation in a carbon balance model. 2. The method is based on regulating gross growth but situations are analys ed where increased senescence of tissue functions as an alternative means o f re-establishing the balance. 3. The model does not aim to be mechanistic but merely to describe the proc ess of regulation, or acclimation to changing environments and situations, as constrained by the carbon balance. The method incorporates parameters th at describe the rate of returning to the balance after disturbance or after a change in the goal, which can be determined empirically. 4. Two models are given as examples of the use of the method, and the requi rements and limitations of control in a carbon balance framework are discus sed. 5. The method is best applied as a technical tool to describe variations an d disturbance in balanced growth models when the variations are present but not very large, in addition, it can be used as a theoretical framework for the analysis of regulation as constrained by the conservation of mass.