Adaptation of the LIGNUM model for simulations of growth and light response in Jack pine

LIGNUM is a whole tree model, developed for Pinus sylvestris in Finland, th at combines tree metabolism with a realistic spatial distribution of morpho logical parts. We hypothesize that its general concepts, which include the pipe model, functional balance, yearly carbon budget, and a set of architec tural growth rules, are applicable to all trees. Adaptation of the model to Pinus banksiana, a widespread species of economic importance in North Amer ica, is demonstrated. Conversion of the model to Jack pine entailed finding new values for 16 phy siological and morphological parameters, and three growth functions. Calibr ation of the LIGNUM Jack pine model for open grown trees up to 15 years of age was achieved by matching crown appearance and structural parameters (he ight, foliage biomass, aboveground biomass) with those of real trees. A sen sitivity study indicated that uncertainty in the photosynthesis and respira tion parameters will primarily cause changes to the net annual carbon gain, which can be corrected through calibration of the growth rate. The effect of a decrease in light level on height, biomass, total tree branch length, and productivity were simulated and compared with field data. Additional st udies yielded insight into branch pruning, carbon allocation patterns, crow n structure, and carbon stress. We discuss the value of the LIGNUM model as a tool for understanding tree growth and survival dynamics in natural and managed forests. (C) 2001 Elsevier Science B.V. All rights reserved.