1. No cutting. 



2. Moderate crown thinning which removed about 30 percent of the basal area and 

 sawtimber volume by cutting defective trees, wolf trees, and additional trees to favor 

 about 80 to 100 of the best trees per acre. 



3. Heavy cutting from above, removing all trees larger than a specified diameter 

 limit which was 16 inches in four tests and 14 inches in one test. This treatment was 

 intended to resemble the "logger's choice" cutting that is commonly applied to these 

 young merchantable stands. 



Treatments were compared on the basis of mean annual growths for 10 years after 

 cutting. Analyses of variance and multiple-range tests were used to test treatment 

 differences . 



The original intent was to establish the tests on farmers ' woodlots to serve as 

 demonstration areas. However, as suitable stands in woodlots were difficult to find, 

 three of the five tests were located on Indian reservations. One test (Tensed, Idaho 

 plots) was never completed because the plot assigned the moderate crown thinning was 

 not cut. Growth data from the incomplete test are presented in table 7 in the appendix. 

 Hov\;ever, these plots were not included in the statistical analyses. 



The five test stands are not exactly comparable in age, species composition, and 

 site index, but as a group they are quite representative of second-growth ponderosa 

 pine stands in the Inland Empire (table 1). 



Table 1 .- -Description of commercial thinning test sites and stands before treatment 











: Date of '■ 



Stand 



: Site 



Av. 



Location : 



Elevation 



: Aspect : 



Soil 



'■ treatment '■ 



age 



■ index ^ 



d.b.h. 





Feet 









Years 





Inches 



Chewelah, Wash. 



1,900 



Southeast 



Sandy - 



1950 



90 



90 



11.9 









loam 











Springdale, Wash. 



2,480 



Flat 



Sandy - 



1950 



90 



100 



14.4 









loam 











Usk, Wash. 



2,100 



Flat 



Sandy - 



1951 



90 



90 



12.7 









loam 











Colbert, Wash. 



1,700 



Flat 



Sandy 



1951 



115 



75 



14.4 



Tensed, Idaho 



2,550 



Flat 



Loam 



1951 



70 



110 



14.5 



^Meyer, Walter H. Yield 



of even-age 



stands 



of ponderosa pine. 



JSDA Tech 





Bull. No. 630, 59 



pp. , illus . 



1938. 













RESULTS 



Growth and development of four experimental stands for 10 years following the 

 cuttings are shown in tables 3 to 6 in the appendix. Growth on the Tensed plots has 

 been measured for only 5 years (appendix, table 7). Board-foot values are important from 

 a practical viewpoint because the principal product currently harvested from ponderosa 

 pine stands is sawlogs. Periodic net annual sawlog increment on the control, moderately 

 cut, and heavily cut plots averaged 338 board feet, 308 board feet, and 161 board feet, 

 respectively (figure 1). The 30-board- foot growth difference between the control and 

 moderately thinned stands was not statistically significant. 



2 



