Table 1. --History and description of uneven-aged study plots 



Plot 



No . Description 



61 Represents virgin ponderosa pine. The south half of the plot was first 

 measured in 1920 and the other half in 1925. Average site index of this plot 

 has been estimated to be approximately 67 by Minor's (1964) site curve. 



62 First measured in 1920. It was salvage cut in 1940 and again in 1953. 

 Average site index is 73 (Minor 1964) . 



71 Had a modified selection cut in 1924, followed by its first measurement in 1925. 

 A timber stand improvement (T.S.I.) cut occurred in 1935, an improvement 

 selection cut in 1946, a precommercial thinning in 1967, and a group selection 

 cut in 1968. The basal area stocking level now established as a goal for this 

 plot is 96 square feet. Average site index is 73 (Minor 1964). 



72 Treatment has been identical to that of plot 71. The basal area stocking level 

 now set for this plot, however, is 70 square feet. Average site index is 70 

 (Minor 1964) . 



The even-aged data came from the Taylor Woods level of growing stock study, located very 

 close to the uneven-aged plots (Schubert 1971), and consisting of 18 plots ranging in size from 

 0.75 to 1.25 acres. These plots represent three replications of six growing stock levels (30, 

 60, 80, 100, 120, and 150 square feet of basal area). The plots were measured in 1962, 1967, 

 and 1972. They were thinned in 1962 and 1972 (the 1962 thinning was before measurement). All 

 trees on the plots were measured. Average site index for the study area is 88 (Minor 1964). 



The attributes measured on each tree include d.b.h., tree condition, crown class (whether 

 a tree was a dominant, codominant, and so forth), crown quality (the condition of the crovm) , 

 and percent of the bole in live crown. On a subsample of the trees, the following additional 

 items were measured: total tree height, crown length, and crown width. 



Data Problems 



While this data source is unusual for the West because it provides both even-aged data and 

 long-term uneven-aged growth data, it also posed numerous modeling problems. A brief discus- 

 sion follows on these problems and the actions taken to minimize them. See appendix A for a 

 more complete discussion. 



1. All of the data used in this study came from a narrow geographic and site range. 

 Therefore, it is recommended that the simulator developed in this study be applied only to 

 stands on the ponderosa pine/Arizona fescue (Pinus ponderosa/ Festuca arizonica) habitat type of 

 northern Arizona. 



2. Because of changes in the lower limit of diameter measurements, only data measured up 

 to 1940 were used to estimate component model parameters. 



3. An intrusion of a major paved highway through all of the uneven-aged plots necessi- 

 tated the removal of some subplots. 



4. As mentioned earlier, a wide range of subplot sizes exists on the uneven-aged plots. 

 To avoid a potential problem of confounding subplot stand differences with subplot size differ- 

 ences, all uneven-aged subplots below 2 acres were eliminated from the data base. 



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