84 



,THE OUTLOOK FOR TIMBER IN THE UNITED STATES 



cubic feet per acre of commercial timberland, but 

 this figure varied from a low of about 3 1 cubic feet 

 on farm and miscellaneous private lands and 42 

 cubic feet on National Forests to a high of 134 

 cubic feet per acre on forest industry lands. 



The low cutting level on farm and miscellaneous 

 lands in this period largely reflected low levels of 

 inventory due to past heavy cutting. The limited 

 harvesting of timber on public lands, despite large 

 inventory volumes, has been a result of long 

 rotations to achieve agency objectives, as well as 

 lower inherent site productivity of many areas in 

 public ownership. 



Projections of available roundwood supplies per 

 acre increase ultimately for all ownerships com- 

 bined, with a narrowing of the range in harvests 

 per acre among the different owner classes. The 

 highest projected output is for industry-owned 

 lands, in spite of a rapidly shrinking inventory, 

 largely due in part to the concentration of the most 

 productive lands in these holdings and relatively 

 intensive management. 



Net Growth in Relation to Removals 



Long-run trends in future timber harvests, 

 after the conversion of most old-growth stands, 

 will be determined essentialfy by trends in growth. 

 Although net growth has been less than harvests, 

 growth has been rising steadily and future sizable 

 increases are projected, particularly in terms of 

 cubic feet (tables 68 and 69, and figs. 38 and 39). 



For all owners combined, a continued excess of 

 removals over net growth is expected for both 

 growing stock and sawtimber over the projection 

 period. Thereafter a prospective drop in National 

 Forest sawtimber production — assuming 1970 

 management levels — would tend to bring removals 

 and growth into balance at some reduced level. 



Net growth per acre. — Net growth per acre on 

 the Pacific Coast has trended upward over the 

 past 20 years as more old-growth timber with 

 low growth rates has been replaced b} r faster 

 growing young trees. For all forest owners com- 

 bined, net growth averaged 45 cubic feet per 

 acre in 1970 (table 74) — about 35 percent higher 

 than in 1952. In future decades net growth for 

 all owners is projected to increase to an average 

 of 59 cubic feet per acre under the assumptions 

 of this base projection. 



Net growth on National Forest lands in 1970 

 was much below that on other ownerships, due to 

 the heavy inventories of old-growth timber on 

 these public lands of generally lower sites. 



Net growth rates of softwood growing stock 

 averaged only 1.1 percent of the softwood inven- 

 tory in 1970 — a consequence of the predominance 

 of old-growth timber with high volumes and high 

 mortality rates. Net growth of softwood growing 

 stock varied from 0.6 percent on National Forests 

 to 2.5 percent on farm and miscellaneous private 

 lands. Over the projection period growth rates 



Net growth and removals of growing stock in 

 the Pacific Coast 



1952 1962 1970 1980 1990 2000 2010 2020 



Figure 38 



Net growth and removals of sawtimber in the 

 Pacific Coast 



softwoods 



-removals 



net growth 



removals 



1962 1970 1980 1990 2000 



Figure 39 



increase on all categories of ownership except on 

 farm and miscellaneous holdings to an estimated 

 average of 1.8 percent by 2020 (table 75). 



Mortality. — Natural losses of softwood timber 

 on all ownerships combined averaged about 20 

 cubic feet per acre in 1970, or about one-third of 

 gross growth (tables 68, 69, and 76). This rela- 

 tively high level of mortality was a result of the 

 preponderance of old-growth timber in this sec- 

 tion, and existing levels of forest protection and 

 management. Mortality on farm and miscellane- 

 ous ownerships was considerably below that on 

 other lands in the 1952-70 period, one factor 

 *being the comparatively j^oung age of stands on 

 these nonindustrial private lands. 



While the projected mortality figures for soft- 

 wood sawtimber show a steady decline over the 

 projection period (fig. 40), there are diverging 

 trends amongst the various ownerships. Projec- 



