TRIM timber projections: an evaluation based on forest inventory measurements.

Abstract

Two consecutive timberland inventories collected from permanent plots in the natural pine type in North Carolina were used to evaluate the timber resource inventory model (TRIM). This study compares model predictions with field measurements and examines the effect of inventory data aggregation on the accuracy of projections. Projections were repeated for two geographic areas with two data aggregation schemes. The sensitivity of the model to harvest was tested with historical and adjusted values. For each simulation, the TRIM growth projection mechanism was tested with two types of yield tables. Yield tables developed from growth data produced projections that were closer to the measured inventory than did yield tables derived from volume data. This study suggests that timber growth measurements should be incorporated into TRIM yield tables when stands have the characteristics found in natural pine in North Carolina. The TRIM system is outlined, and the methods used to derive yield tables are discussed.

Citation

Mills, John R. 1989. TRIM timber projections: an evaluation based on forest inventory measurements. Res. Pap. PNW-RP-408. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 27 p