These situations are detected and automatic tallies scheduled when certain 

 threshold values are exceeded. 



If 10 to 30 percent of either the trees per acre or the total cubic-foot vol- 

 ume is removed, a single regeneration tally is scheduled. A tally sequence 

 is scheduled when more than 30 percent of either the trees per acre or the 

 cubic-foot volume is removed. Nothing is scheduled if removals are less than 

 10 percent. The default values of 10 and 30 percent can be changed by the 

 user. 



Site Preparation Site preparation is a very important predictor of regeneration success, 



species composition, and growth rates. Most model users either specify the 

 percentages of site preparation in the prescription, or they code plot-by-plot 

 site preparations on stand examination records. For model users who do 

 not specify site preparation(s), equations were developed to predict default 

 probabilities. Plots used to develop these equations came from stands not 

 deliberately prepared mechanically or by burning. 



Default site preparation equations are given in appendix B, table 20. Only 

 aspect, slope, residual basal area, elevation, and habitat type series are im- 

 portant independent variables. 



The Prognosis Model was first developed for northern Idaho and adjacent 

 portions of Montana and Washington (Stage 1973; Wykoff and others 1982). 

 The Prognosis Model has also been calibrated for other geographic areas. 

 Geographic versions are called variants. 



Prognosis Model variants that do not have a calibrated regeneration model 

 have an abbreviated version of the regeneration model. In these variants, 

 creation of tree records representing natural regeneration is specified by the 

 user in a manner similar to planting (Ferguson and Crookston 1991). Users 

 describe expected regeneration in terms of species and density. Expected 

 regeneration is estimated by the user using historical data or experience. 



Some Prognosis Model variants represent species that sprout from roots 

 or stumps of harvested trees. For these variants, subroutines that create 

 tree records for sprouts were added to the regeneration model. Information 

 about trees removed at the beginning of the cycle is stored for use at the end of 

 the cycle when the number and size of sprouts is predicted. Each variant 

 will be different because of the species and environment being represented, 

 but once equations predicting the number and size of sprouts are developed, 

 they can readily be inserted in the regeneration model. 



DISCUSSION 



Version 2 of the Regeneration Establishment Model became available 

 with the release of version 6.1 of the Prognosis Model. Version 2 of the re- 

 generation model covers five habitat type series in Montana and in central 

 and northern Idaho. Abbreviated regeneration models are available with 

 Prognosis Model variants covering other locations in the Western United 

 States. 



The regeneration model is based on a sample size of 12,128 Vaoo-acre plots 

 from 537 stands. Data represent all aspects, 0-110 percent slopes, 0-390 

 square feet of residual overstory basal area, 2,400-7,400 feet elevation, four 

 site preparation methods, and 0-16 years of budworm defoliation. Stands 

 were chosen using stratified random sampling procedures. Stratification 



Regeneration 

 Model Variants 



Regeneration 

 Sprouts 



37 



