A model for assessing the impact of atmospheric deposition on regional forest inventories

A model for estimating the impact of atmospheric deposition on regional forest inventory was developed, and combines a regional inventory projection model, a modified yield function which includes crown length as a predictor variable and exogenously determined timber harvests. The effect of atmospheric deposition on forest growth is simulated by varying crown length, and the inventory impact is the difference between inventory without and with varied crown length. The model is demonstrated by projecting the Commonwealth of Virginia's softwood forest inventory in 5-year intervals to the year 2035. A one-foot reduction in crown length causes a 0·7 to 1·7% reduction in inventory, depending on ownership. Inventory reductions of 1·7 to 8·7 and 4·5 to 17·8% are estimated for 5- and 10-foot crown reductions. However, models which account for market interactions halve the reductions.