Computer simulation of Douglas-fir tree and stand growth

Graduation date: 1972A mathematical model has been developed to describe the growth\ud of individual Douglas-fir trees under a variety of stand conditions and\ud management schedules. The model was developed using empirical\ud data from open-grown trees and reducing growth capacities of height,\ud stem, and crown as functions of intertree competition indices. Any\ud initial pattern of spacing for up to 30 trees may be assumed. The\ud user must supply the stem coordinates, estimate of site, and estimate\ud of the number of years to reach a height of 4. 5 feet for each tree.\ud Any intensity of thinning schedule may be requested up to an annual\ud basis. The model simulates the form of the entire bole and crown for\ud up to 80 years of growth.\ud All calculations were performed on a CDC 3300 electronic\ud computer. Individual tree and stand summaries can be listed for any\ud periodic interval of interest:. A Cal-Comp plotter output is available\ud for a complete stem analysis, output for one specified tree in the stand.\ud All coefficients for regressions fitted in the model are listed in a\ud separate file for easy access and modification.\ud The mathematical model developed here satisfactorily describes\ud the growth of Douglas-fir stands on an individual tree basis for a wide\ud range of stand conditions and management schedules. It was tested\ud against seven permanent field plots for a range of conditions in both\ud Oregon and Washington. Although predictions were not accurate there\ud are no gross errors and the results demonstrate the sensitivity and\ud stability of the model.\ud The model developed here can be a valuable tool to the forester\ud in training students, analyzing basic growth relationships, testing\ud management schedules, evaluating fertilization and irrigation\ud responses, and planning allowable cuts, sustained yields, and\ud economic returns of forest products