Thuja plicata/Pachistima myrsinites Thpl/Pamy 

 western redcedar/pachistima myrsinities 



Since there were no criteria for stand selection other than past management or 

 planned future management, many different types of stands were selected. Both stand 

 size and number of sample points per stand were not fixed for the study. Stand age 

 was quite variable, ranging from 10 years to 200 years (table 1) . 



As would be expected, stand characteristics differ for each stand. Mean stand 

 diameters range from 0.9 to 16.3 inches (2.29 to 41.4 cm) (table 2). Both trees per 

 acre and accretion-^ vary from stand to stand. Because of ingrowth and/or mortality, 

 mean diameters in some of the stands are smaller for the second measurement. 



Because of the nature of the data and the lack of an appropriate experimental 

 design, we are presenting the results as a case study. The results are for the 

 stands examined and the data should be extrapolated to other stands and conditions 

 with caution. 



ANALYSIS 



The analysis involved summarizing data for the 36 stands and making appropriate 

 comparisons. When each stand was chosen for inclusion in the study, the crop trees 

 were tagged and permanently marked. To make valid comparisons between the first and 

 second measurement, only crop trees were used in the thinned stands. In the unthinned 

 stands, the entire stand as it existed was used. Diameter growth and height growth 

 were converted to 10-year periods for ease of comparison. Incomplete records--that 

 is, trees dying during the study- -were dropped from the diameter and height growth 

 calculations. A least squares mean separation procedure (SAS Institute 1979) was 

 used to separate the growth means for the habitat types. 



To better show the impact of the diameter and height growth changes, each stand 

 was projected into the future using a stand prognosis model (Stage 1973). These 

 projections are the best estimate possible for the potential growth of the stands. 



RESULTS 

 Diameter Growth 



Tree size and age are very important in determining tree growth rates. Therefore, 

 to make comparisons among habitat types, the diameter growth means were adjusted for 

 both age and diameter of the trees at the time of the first measurement. In the 

 analysis of covariance, age and initial diameter were both significant (P <_ .05) in 

 explaining diameter growth. These adjusted growth means can be compared allovvfing for 

 different tree ages and diameters. 



The Pipo/Syal h.t. had the smallest adjusted 10-year diameter growth mean, 0.68 

 inches (1.73 cm). The Ahla/Pamy h.t. had the largest 10-year diameter growth mean, 

 4.26 inches (10.82 cm) (table 3). The adjusted means can be separated into distinct 

 habitat type groups based on 10-year diameter growth using the least squares mean 

 separation procedure. These were: (1) Pipo/Syal; (2) Abgr/Pamy , Thpl/Pamy; (3) 

 Psme/Phma , Tshe/Pamy , Psme/Syal , Abla/Vasc , Psme/Caru-Aruv; and (4) the Ahla/Pamy 

 h.t. 



Periodic annual cu ft volume growth based on 5-year period excluding ingrowin. 



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