Overestimation 

 of the timber 

 growing base 



Former timber inventories on the six Na- 

 tional Forests that were analyzed indicated an 

 aggregate timber growing base area of 4.1 mil- 

 lion acres. However, this timber growing base is 

 reduced to 3.2 million acres when careful ac- 

 count is taken of soil-slope conditions, land 

 productivity, and land use. In other words, the 

 area suitable and available for growing tree 

 crops on these six National Forests is 22 per- 

 cent less than had been previously estimated. 



The timber growing base was not overesti- 

 mated to the same degree on all of the six For- 

 ests. On the Gifford Pinchot Working Circle, 

 the decrease is only 11 percent as compared to 

 40 percent decrease on the Arapaho National 

 Forest. (Data for each of the six areas are pre- 

 sented elsewhere in this report.) The significant 

 point is that, in every case, a more careful and 

 critical look at availability, growth capacity, 

 and land suitability (primarily stability) re- 

 sulted in a significant reduction of the area 

 deemed suitable and available for timber 

 growing. 



These reduction figures did not come as a 

 surprise; National Forest administrators have 

 recogniz.ed this problem for several years and 

 have been decreasing the area figures used in 

 calculating allowable cuts. This study is, there- 

 fore, distinguished primarily by the fact that it 

 represents the most systematic effort to iden- 

 tify and measure the factors that reduce the 

 land base for timber growing on the National 

 Forests. 



Much of the land excluded from the timber 

 growing base by the tighter standards and more 

 systematic classification of this study is on the 

 lower end of the productivity scale. Thus, the 

 22 percent reduction in timber growing base 

 area on the six Forests does not indicate that 

 the timber producing capability will be reduced 

 by that amount. Data inadequacies prevented 

 determining the exact effect of area reductions 

 on yield capabilities for all of the National For- 

 ests. However, on the Coconino National For- 

 est the timber growing base area was reduced 

 by 28 percent, but the growth capability of 

 that National Forest was reduced only 18 per- 

 cent. On the Gifford Pinchot Working Circle 

 the decline in growth capability was 7 percent 

 as compared with 11 percent decrease in 

 acreage. 



The factors that affect classification of the 

 timber growing base vary so widely from place 

 to place that few generalizations are safe. Land 

 use considerations of one sort or another were a 

 big item on all but one National Forest. How- 

 ever, land instability, low productivity, and un- 

 economic units are all important to different 

 degrees on different Forests. 



Following are the percentages of the total 

 0.9 million acres eliminated from the timber 

 growing base of all six National Forests. Please 

 remember that we have no basis lor saying just 

 how representative is each of these percentages. 

 They are presented only to indicate that each 

 factor is important. 



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