Procedure for 

 timber inventory 



Timber inventories generally are based on a 

 double sampling scheme. Initial sampling on 

 aerial photos involves classifying a large num- 

 ber of photo points into broad forest land 

 classes (nonforest, nonproductive forest, and 

 productive forest). For field sampling, the pro- 

 ductive forest category is further categorized 

 into a number of strata based on type stand or 

 volume of timber. The field samples provide: 

 (1) information to verify the photo point classi- 

 fication; (2) tree measurement data from which 

 estimates of timber volume can be made; and 

 (3) general information on the condition of the 

 forest. 



This double sampling procedure was used on 

 all but the Gifford Pinchot study unit where a 

 single sampling procedure was employed using 

 only field samples. Of the timber inventories 

 used, none were designed to consider all the 

 land and land use attributes evaluated in this 

 study. Information on these attributes was de- 

 veloped afterward and the inventory data re- 

 compiled to reflect the influence of land and 

 land use characteristics. 



For this study, map data were used and 

 photo points for each study unit were further 

 classified to reflect land use and land character- 

 istics. Basic information was obtained from: 

 timber stand and/or type maps, multiple use 

 land management plan maps, and maps show- 

 ing soil type and land stability situations. Mul- 

 tiple land use management maps for the study 

 areas were updated to indicate all forest land 

 where management to meet nontimber land use 

 commitments would preclude or restrict tim- 

 ber production. In addition, management in- 

 tent was specifically described in detail so that 



impact on timber use and yield could be 

 assessed. 



Another map was prepared for the study 

 unit showing undeveloped land for which no 

 access was planned during the next 10 years. 

 Also shown were areas of peculiar ecology or 

 soil situations that could not be used for timber 

 production because of unsolved timber grow- 

 ing problems. In addition, the timber inventory 

 on the study unit was supplemented by the col- 

 lection of data on stocking capability and de- 

 scription of small isolated patches and stringers 

 of trees. 



DOUBLE SAMPLING PROCEDURE 



The stratification procedure and results 

 with the double sampling system are illustrated 

 here by using data from the East Klamath 

 Working Circle, Klamath National Forest, lo- 

 cated in the Upper Klamath River area of 

 northern California and southern Oregon. This 

 Working Circle, 551,099 acres in size, is domi- 

 nated by steep slopes, though the soil is rela- 

 tively stable. The reconnaissance soil survey in- 

 dicated that most of the forest land is usable 

 now for timber production or potentially us- 

 able with some improvements in technology. 

 Some of the area, particularly at higher eleva- 

 tions, is rugged country having productive for- 

 est land that occurs in pockets and patches in- 

 termixed with nontimber base forest land and 

 bcirren, rocky areas. At lower elevations the for- 

 est cover is broken, with forest areas inter- 

 mingled with nonforest land. The timber re- 

 source on the Working Circle was inventoried 

 for timber in 1968. Utilizing recent aerial 



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