Incorporating interstate trade in a multi-region timber inventory projection system

An inter-regional trading model for roundwood products was developed that recognizes the importance of demand centers (centers of forest products manufacturing activity) and inventory in forecasting future harvests and trade flows. A gravity model was constructed that considers the relative position of each region vis-A-vis all others as a producer of stumpage and as a consumer of roundwood products. The gravity model was incorporated in a multi-region version of DPSupply (Teeter 1994, Zhou and Teeter 1996, Zhou 1998) referred to as the Interregional DPSupply System (IDPS). Projections for growth, harvest, and trade in forest products were made for the 13 states of the southern region through 2025. Aggregate trends in inventory are similar to those reported in the Southern Forest Resource Assessment (Wear and Greis 2002). Inventory trends by product (pulpwood, sawtimber) and type (hardwood, softwood) differ by state and are used to illustrate the advantages of explicitly recognizing interregional trade in the projection system.