species composition, habitat type, and so on. The Northern Region (Region 1) 

 and Intermountain Region (Region 4) of the Forest Service, U.S. Department of 

 Agriculture, have a large number of managed stands that can be retrospectively 

 examined because there are adequate historical records. Additional stands 

 with adequate historical records are available from other major ownerships, 

 such as Potlatch Corporation, Idaho Department of Lands, Montana Depart- 

 ment of Forestry, Champion Corporation, or the Bureau of Indian Affairs 

 and Bureau of Land Management in the U.S. Department of the Interior. 



These three factors enabled a retrospective examination of regeneration 

 success in cutover stands and the development of a quantitative regenera- 

 tion model. The Regeneration Establishment Model described in this paper 

 is a part of the Prognosis Model (Stage 1973; Wykoff and others 1982). The 

 Regeneration Establishment Model predicts establishment of new trees that 

 are added to the inventory of trees being projected by the Prognosis Model. 

 The Prognosis Model implements user-specified management prescriptions 

 and predicts accretion and mortality for the stand. The Prognosis Model with 

 the Regeneration Establishment Model can be useful to managers in the fol- 

 lowing situations: 



1. To decide which of several prescriptions best meets reforestation objectives. 



2. To link regeneration to predictions of long-term growth and 3deld. 



3. To predict regeneration in long-term projections of succession or uneven- 

 age management. 



4. To help develop harvesting schedules. 



5. To help in other areas of forest planning where regeneration is important 

 for watershed, wildlife, esthetics, and so on. 



Version 1 of the Regeneration Establishment Model was developed for the 

 grand fir-cedar-hemlock ecosystem in northern Idaho and adjacent portions 

 of Montana and Washington (Ferguson and others 1986). Version 2 of the 

 model, reported in this paper, expands the geographic area, includes additional 

 habitat types, and includes the influence of western spruce budworm (Chor- 

 istoneura occidentalis) on regeneration success. 



Version 2 of the Regeneration Establishment Model is calibrated for west- 

 em Montana as well as central and northern Idaho. Figure 1 shows the loca- 

 tions of sampled stands. Habitat type series included in the model are the 

 Pseudotsuga menziesii, Abies grandis, Thuja plicata, Tsuga heterophylla, 

 Abies lasiocarpa, and some of the Tsuga mertensiana series. 



The effects of western spruce budworm defoliation on regeneration success 

 are represented in the regeneration model. Western spruce budworm reduces 

 growth, crown volume, and cone crops of host trees, and increases top-kill, 

 mortality, deformities, and predisposition to other insects and disease. Host 

 species in the study area are western larch {Larix occidentalis), Douglas-fir 

 (Pseudotsuga menziesii), grand fir (Abies grandis), Engelmann spruce (Picea 

 engelmannii), and subalpine fir (Abies lasiocarpa). 



To be consistent, we use scientific names and four-letter abbreviations 

 when discussing habitat types. An example is the Abies grandis/Clintonia 

 uniflora habitat type, abbreviated ABGR/CLUN. When discussing tree spe- 

 cies, we use the common name; for instance, grand fir. 



This paper presents details about data collection, predictive equations, model 

 development, and model behavior. A user's guide to version 2 of the Regen- 

 eration Establishment Model is available (Ferguson and Crookston 1991). 

 Silvicultural interpretations of the model v^dll be presented in another paper 

 (Carlson and Ferguson in preparation). 



2 



