Comparison of height growth and growth intercept models of jack pine plantations and natural stands in northern Ontario

Accurate estimates of forest productivity are required for sustainable forest management. Sixty-five jack pine (Pinus banksiana Lamb.) plantations (< 50 years of age) were sampled to develop height growth and variable growth intercept (GI) models for jack pine plantations in northern Ontario, Canada. Based on the residual plots and model-fitting statistics, these models can be recommended for estimating site index (SI) of young (< 40 years) jack pine plantations. To compare SI of plantations with that of natural stands, we used stem-analysis data from 383 plots of natural jack pine stands (aged 50-157 years) from the same geographic region to develop the GI models for natural stands. Also, polymorphic SI curves were developed for young (< 40 years) plantations in northern Ontario. These SI curves were different from those for natural stands. Jack pine plantations had a higher site quality (SI) than did the original natural stands on the similar sites. The SI curves developed from natural stands should not be used to predict growth and yield of jack pine plantations before they are calibrated for jack pine plantations. These GI models will be used to estimate SI for silviculture and forest-management planning.