CULL FACTORS FOR SITKA SPRUCE, VffiSTERF HEI4LCCK, 



AND 

 WESTERN REDCEDAR IN SOUTHEAST ALASKA 



By James W. Kiininey 2/ 



INTRODUCTION 



An unknown quantity has for many years been one of the principal 

 problems in inventorying the timber of Southeast Alaska. The unknown 

 is the extent of defect in the region's vast timber stands. This pub- 

 lication presents a tool for estimating the defect; cull factors are 

 given here for the three principal tree species as determined by a 

 study made at eight locations in these stands. 



Cull is that part of a living tree which is not merchantable 

 because of defect. When the amount of cull is expressed as a percent 

 of the gross volume of a tree, the percentage is termed the cull 

 factor . 



Within a species the average amount of cull in a tree increases 

 with its age. However, it is impossible or impracticable to determine 

 the age of each sample tree when cruising. Since tree size is ordinar- 

 ily correlated Td.th age and is readily measured by cruisers, tree 

 diameter has been employed in the preparation of these cull factors. 



Cull was studied in Sitka spruce (Picea sitchensis (Bong.) 

 Carr.), western hemlock ( Tsuga heterophylla (Raf.) Sarg.), and western 

 redcedar ( Thu.j a plicata Donn) . Cull discount factors for each of 

 these species x^^ere prepared for trees of various diameters. They were 

 based on both board-foot and cubic-foot gross volumes to fixed top- 

 diameter limits and to average top limits utilized in the logging 

 areas. Besides these flat factors similar discount factors were pre- 

 pared for the amount to be expected when certain indicators of cull, 

 such as conks or wounds, are found on the outside of the trees. Cull 

 factors of this latter type are termed cull indicator factors. 



All of the various cull factors x-jere prepared primarily for use 

 in the Forest Survey in Southeast Alaska. They are published here for 

 use of other workers in the forests of this area. 



1/ This project carried out by James ^1. Kimmey, Pathologist of 

 the California Forest and Range Experiment Station, with the coopera- 

 tion of the Alaska Forest Research Center. This report is distributed 

 by the Alaska Forest Research Center, Juneau, Alaska. 



