Simulation models : a useful tool in the evaluation of planted coastal Douglas-fir silvicultural management

• Main Author: Onate, Nilda Elvira
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/6333

This study showed how selected growth and yield simulations models compare in predicting the results of a set of prescriptions for planted stands of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco). Estimates of growth rate, mean diameter, and yield were compared over a rotation for various sites. An economic analysis of the projected estimates was conducted with particular focus on a site index of 30 m. The selected models showed a wide variation predicting the effects of treatments (individually or in combination) and in predicting yields. This variation was attributed mostly to the databases used to develop the mathematical expressions which predict growth. The response to commercial thinning, in particular, was based on diverse assumptions among the models. The growth resulting from the simulated use of a fertilizer differed in assumptions regarding the duration of the effects of the fertilizer, the increase and the acceleration of the volume growth rate, and the amount of volume produced. Model predictions were mostly in agreement for the simulation of stands established at low initial densities (400-1100 sph). Model predictions of total standing volume were in agreement for almost all the prescriptions for site index 30 m. The economic evaluation determined the best combination of a sequence of scheduled activities. Precommercial thinning in combination with commercial thinning proved to be a financially attractive management alternative for initial planting densities of 2500 sph. A stand planted at 1100 sph and commercially thinned at ages 40, 50 and 60 showed the best return, although entry at age 60 produced the highest net benefits. Stands planted at 2500 and 1600 sph and precommercially thinned did not offset the costs incurred in the prescription. Stands widely planted (400-1100 sph) did not generate an acceptable return on the investment.