STUDY OBJECTIVES 



Recent publications (USDA Forest Service 1975, 1976; Alexander and Edminster 1977a, 1977b; 

 Hann and Bare 1979) suggest a renewal of interest in uneven-aged forest management. Hann and 

 Bare (1979) reviewed major questions facing a forest manager interested in practicing uneven- 

 aged management and summarized the analytical tools currently available to answer these ques- 

 tions. They demonstrated the important role stand development simulators play in making 

 decisions using some of the more recent analytical tools. The construction of appropriate 

 stand development simulators is tlierefore a prerequisite to the application of these analytical 

 tools . 



A number of simulator types have been developed in recent years (Munro 1974) . But techno- 

 logical limitations of the available uneven-aged analytical tools require using whole-stand 

 simulators that characterize the stand by at least the number of trees in various diameter 

 classes (Adams 1974; Adams and Ek 1974, 1976; Hann 1978). With this constraint, the objectives 

 of this study became: 



1. To examine the dynamics of uneven-aged stand development in the ponderosa pine/ 

 Arizona fescue habitat type by developing a whole-stand simulator that would have the potential 

 for aiding forest managers in answering questions concerning uneven-aged management. Ponderosa 

 pine was chosen because it is one of . the few species in the West for which permanent plot data 

 exist for both even- and uneven-aged stands. 



2. To examine whether even- and uneven-aged stand development in ponderosa pine/Arizona 

 fescue could logically be interrelated and, if so, to develop the whole-stand simulator to be 

 applicable to both. 



5. To validate the whole-stand simulator by analyzing its capability to predict both 

 average plot and average stand development. 



PREVIOUS UNEVEN-AGED, WHOLE-STAND SIMULATORS 



Two approaches to the development of uneven-aged, whole-stand simulators have been 

 reported. The first approach uses differential equations and the second uses difference 

 equations to characterize stand dynamics. The differential equation approach is based on using 

 instantaneous rate equations to model stand dynamics. Two alternate techniques exist for 

 parameter estimation of the instantaneous rate equations. In the first technique, modelers 

 approximate the instantaneous rates through use of periodic rates that have been converted 

 to an annual basis, and then estimate the parameters through regression analysis (Moser and 

 Hall 1969; Moser 1972, 1974). If the length of the growth period is short and if the instan- 

 taneous rates do not change drastically within the period, then this technique can provide 

 satisfactory estimates of the instantaneous rate equations. The second technique uses the 

 multipoint boundary value method to develop parameter estimates of the instantaneous rate 

 equations (Leary 1970) . This process is a common numerical analysis method but requires data 

 from at least three different points in the development of the stand. While Leary' s (1970) use 

 of this method was in even-aged stands, it would also be appropriate in uneven-aged stands. 



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