Modelling canopy growth and steady-state leaf area index in an aspen stand

We developed a canopy growth model to analyse the importance of different s tructural properties in the formation of equilibrium leaf area index in a P opulus tremula canopy. The canopy was divided into vertical layers with the growth and structural parameters of each layer dependent on light conditio ns. Horizontal heterogeneity was considered through clumping parameter. The principle growth parameters considered were long shoot bifurcation ratio, number of short shoots produced by one-year-old long shoot, short shoot sur vival and number of leaves per shoot. Parameter values and relationships ar e based on field measurements of an aspen stand in Jarvselja, Estonia. Depe nding on initial conditions, leaf area index reaches the steady state in 5- 20 years. The value of initial density of long shoots affects the time need ed to achieve equilibrium but has little influence on final LAI value. The most influential parameters in predicting the final LAI are thus of the rel ationship between long shoot bifurcation ratio and light.