HEIGHT GROWTH MODELING USING 2ND-ORDER DIFFERENTIAL-EQUATIONS AND THEIMPORTANCE OF INITIAL HEIGHT GROWTH

In a study of height growth patterns of quaking aspen (Populus tremulo ides Michx.) in Minnesota, Wisconsin and Michigan, we represented the height-age pattern using a second order ordinary differential equation with environmentally governed parameters. Solving a second order diff erential equation that has been converted to a system of two first ord er equations requires knowledge of, or information on, initial conditi ons for both state variables, height and height growth. We used the na tural boundary condition, h(t = 0) = 0. Initial conditions for the sec ond state variable, height growth, were estimated when fitting the equ ations to observations. This paper reports our research to predict the initial height growth from stem analysis data, and to assess the sens itivity of predicted height to differences in initial condition estima tes. We found initial height growth to be the single most important 'p arameter' to be estimated in our model. (C) 1997 Elsevier Science B.V.