Table 1. --Variance ratio, expected reduction in field plots, and rank of the 

 field-stratification methods for volume estimating 





: Stratification method 



: Cubic volume 





: Saw log volume 



J.MU • 



: Description 



: Number 

 of 



: strata 



' Variance 

 ratio 



Reduction : 

 in field : 

 plots : 



Rank 



[ Variance j 

 ' ratio 



Reduction : 

 in field : Rank 

 plots : 









Percent - - - - 





- - - - Percent - - - - 





None 





1 ] no 



1UU 







1 1 DO 





1 



Stand size and 

















density 



i n 

 1U 



46 



54 



2 



49 



51 3 



o 

 z 



Stand size 



4 



53 



47 



Q 

 O 



52 



48 4 



3 



Density 



3 



91 



9 



7 



96 



4 7 



4 





i n 



91 



9 



6 



89 



11 6 





Site 



6 



90 



10 



5 



87 



13 5 



6 



Management 

















category 



5 



56 



44 



4 



48 



52 2 



7 



Cubic volume -- 

 500-cubic-foot 

















class 



11 



1 



99 



1 



14 



86 1 





1 Total unstratified 



variance : 



Cubic, 2, 



122, 100; Saw log, 



69,451,100. 





NOTE: Method 7 is academic for cubic volume since the stratification was made by the 

 same volumes used in computing variance. 



obtained from photo measurement. In the case of species , field classification showed even 

 less gain than that made on photos. Quite obviously, stratification by these traditional schemes 

 even through use of field measurements does not equal the gain possible by use of volume strata 

 and aerial photo measurements. Comparison of cubic and saw log volume data (table 2) indi- 

 cates cubic- volume classes are just as useful for saw log volume, and therefore the following 

 comparisons will be made on the basis of cubic- volume classes only. Since this study considers 

 combined management and volume inventories, the next step is to evaluate the methods used in 

 estimating the areas needing management . 



RELATIVE VALUE IN ESTIMATING AREAS NEEDING HARVEST 

 OR OTHER MANAGEMENT TREATMENT 



For this purpose there is no readily measured unbiased index comparable to the variance 

 used in volume estimating. A widely accepted method of evaluating photo stratification for area 

 estimating compares photo and field classifications by means of Chi-square test. This test 

 assumes the traditional field classifications are more closely related to the desired manage- 

 ment classifications than are any made on aerial photos . In the light of the volume analyses 

 this assumption seems unwarranted. 



A second less familiar approach assumes the superior stratification scheme will be that 

 one which confines the plots on which management treatment is needed to the fewest possible 

 strata. This evaluation made through use of Bartlett's test for homogeneity of variance can be 

 used equally well on both field and photo schemes. For example: Assume two photo-classifica- 

 tion schemes each having 10 strata are used to classify an area. Each scheme is sampled 



8 



