Diameter growth models using minnesota forest inventory and analysis data

The Forest Inventory and Analysis (FIA) program of the USDA Forest Service North Central Research Station (NCRS) has begun replacing the 12-to 13-yr p eriodic inventory cycles for the states in the North Central region with an nual inventories featuring measurement of approximately 20% of all plots in each of the 11 states each year. State reports on summaries of the forest resources will be produced every 5 yr. As a method of updating information on plots not visited in the current year, NCRS is developing nonlinear, ind ividual-tree, distance-independent annual diameter growth models for specie s groups. The models, formulated as the product of an average diameter grow th component and a modifier component, were calibrated on Minnesota FIA dat a from stands that were generally undisturbed, of mixed ages and of mixed s pecies. The dependent variable is annual diameter growth. The independent v ariables include crown ratio, crown class, stand basal area, stand basal ar ea larger than the subject tree, physiographic class, and latitude and long itude of plot locations. The model predictions at both the individual-tree level and plot level have negligible bias, and the models may be easily rec alibrated to include new data sets obtained from the annual inventories.