The third summary shows all trees less than 3.0 inches d.b.h. that are in 

 the Prognosis Model tree list. This provides a view of all regeneration cur- 

 rently in the stand. Trees may be from a stand inventory, from a previous 

 tally of the regeneration model, and from the current tally of the regenera- 

 tion model. 



Example 

 Projection 



Comparison of 

 Habitat Types 



MODEL BEHAVIOR 



In this section we use the regeneration model to show example projections. 

 Examples include the default conditions that have been used to illustrate 

 equations, a comparison of five habitat t3^es, and an example of the effects 

 of western spruce budworm. 



This projection is the same stand used to illustrate equations — a hypothetical 

 clearcut in the Idaho Panhandle National Forests, Abies grandislClintonia 

 uniflora habitat type, north aspect, 30 percent slope, 3,500 feet elevation, no 

 planting, and no site preparation. 



The computer file needed to make this projection (called keyword records 

 in the Prognosis Model system) is shown in figure 15. Refer to Wykoff and 

 others (1982) and Ferguson and Crookston (1991) for coding instructions. The 

 default cycle length for the Prognosis Model is 10 years, so regeneration will 

 be predicted at 10 and 20 growing seasons since the disturbance in 1990. 



Output fi'om the regeneration model is shown in figure 16. New tree records 

 are added at the end of the Prognosis Model cycle. There have been 10 growing 

 seasons between the "spring" of 1990 and the "fall" of 1999. The new regenera- 

 tion is added at the end of the cycle so these trees are part of the stand when 

 silvicultural prescriptions are simulated at the beginning of the next cycle. 



After 10 growing seasons, the probability of stocking is 0.7380 and regenera- 

 tion density is 772 trees per acre. Of the 772 trees, 562 are best trees. Spe- 

 cies composition of best trees is 57 percent grand fir, 22 percent Douglas-fir, 

 9 percent western white pine, 5 percent western larch, and less than 5 percent 

 each of Engelmann spruce, lodgepole pine, and ponderosa pine. 



Aft«r 20 growing seasons, the probability of stocking is 0.8631 and 309 more 

 trees have become established, 209 of which are best trees. There are now 

 989 trees <3 inches d.b.h. in the Prognosis Model tree list. Some of these 

 trees are from tally 2 and some are from tally 1. 



Here we show how regeneration model projections vary with habitat type 

 and elevation. Five projections were made, changing only habitat type and 

 elevation between each projection. Other variables held constant were Idaho 

 Panhandle National Forests, north aspect, 30 percent slope, no planting, no 

 residual overstory basal area, no site preparation, and 10 years since harvest. 

 The five projections were a Pseudotsuga menziesii/Physocarpos malvaceus 

 habitat type at 3,000 feet elevation, an Abies grandislClintonia uniflora habitat 

 type at 3,500 feet, a Tsuga heterophylla/Clintonia uniflora habitat type at 

 4,000 feet, an Abies lasiocarpa/Clintonia uniflora habitat type at 5,000 feet, 

 and an Abies lasiocarpa/Xerophyllum tenax habitat type at 5,500 feet. 



Results of these projections are shown in table 6. The Pseudotsuga menziesiil 

 Physocarpos malvaceus habitat type has the lowest probability of stocking 

 (0.2596) and density (195 trees per acre) of the five projections. The number 

 of species present in the stand is limited because of the habitat type. The 

 Abies grandislClintonia uniflora habitat type has a probability of stocking 



29 



