Interior Alaska 



The big event of 1956 was the appropriation of funds to begin a forest 

 inventory of interior Alaska. The area to be inventoried encompasses 

 about 230 million acres, some of it 100 or more miles north of the 

 Arctic Circle. 



Activities in 1956 included an investigation of inventory problems cul- 

 minating in the writing and approval of a working plan for the inventory 

 project. A start was also made on the collection of volume table data. 

 The Bureau of Land Management is cooperating informally with the Forest 

 Service to make this program a success. 



The biggest problem facing the Survey was the almost complete lack of 

 volume tables, cull estimates, growth and yield tables, and suitable 

 aerial photography. The Bureau of Land Management had constructed local 

 volume tables for white spruce and paper birch, but these were not adapt- 

 able to an extensive inventory. Consequently, the following work was 

 begun or completed in 1957: 



1. A comparative analysis of three aerial film types--inf rared, pan- 

 chromatic, and color--to determine which was best suited for inter- 

 pretation of Interior tree species was completed. No significant 

 difference was found between the three film types tested. All were 

 equally efficient for identification of tree species and measurement 

 of tree heights. Only four commercial tree species will be recog- 

 nized in the Interior survey: paper birch, balsam poplar, quaking 

 aspen, and spruce (black spruce and white spruce have been combined). 

 Since there were basically only four tonal or color differences and 

 only four crown variations, one film type was found to be as 

 efficient as another for interpretation purposes. 



2. An analysis of defect on 587 felled trees including four species was 

 started to obtain applicable cull factors. 



3. Determination was made of criteria for the identification of denuded 

 but productive forest land from aerial photos. (Fires have burned 



an average of one million acres per year, according to Bureau of Land 

 Management records. Much of this area is forest land.) 



4. Measurements of the 587 trees mentioned above were made for the con- 

 struction of cubic foot and board foot volume tables. Construction 

 of tables will continue. Cubic foot volume tables from a 1.0-foot 

 stump to a 4.0-inch top d.i.b. correlated with diameter at breast 

 height and total height was constructed by adjusting similar volume 

 tables published by the British Columbia Forest Service. Tables 

 were constructed for Interior spruce, balsam poplar, and paper birch- 

 quaking aspen. 



5. Stand volume data were collected for the construction of aerial photo 

 stand volume tables. This will continue. 



