Validation of two growth and yield models on red pine plantations in Michigan

Two red pine thinning study sites were used to validate two different forest growth and yield computer models, the Forest Vegetation Simulator (FVS) Lakes States variant, an individual tree model and Red Pine Al Lundgren (RPAL) a stand level model. Both study sites had been established as red pine plantations in the 1930's and became thinning study sites in the 1960's. Approximately every five to ten years (between 1964, 1965 through 1991, 1992) the stands were thinned and individual tree measurements were taken on every tree in the study. Both growth models "grew" the data from the second inventory date through the last inventory. The simulated estimates of diameter at breast height (for FVS), trees per acre, and basal area were compared to the actual measurements. Two types of simulations were projected using FVS; with diameter growth calibration and without diameter growth calibration. One type of RPAL simulation was run.; FVS predicted more accurate results then RPAL for trees per acre but not necessarily basal area per acre. FVS predict more accurately dbh and basal area per acre with dbh growth calibration turned on, it had little to no effect on more accurately estimating mortality on either site. With calibration turned on FVS predicted up to twenty seven years of growth with an absolute mean error less than 1.0 inch.