Although less pronounced than the projected geo- 

 graphic shifts in softwood supplies, an increased 

 share of the hardwood roundwood supplies is also 

 projected to come from the South, from 51 percent in 

 1976 up to 59 percent (5.2 billion cubic feet) in 2030. 

 The North's share shows a corresponding drop from 

 46 to 40 percent (3.5 billion cubic feet) in 2030. The 

 shift in hardwood sawtimber supplies toward the 

 South is greater than the shift in roundwood supplies. 

 The cause of this geographic shift is a slower increase 

 in supplies from the farmer and other private owner- 

 ships in the North. This presumably reflects differ- 

 ences in the importance of nontimber management 

 objectives in the two sections. Overall, however, the 

 farmer and other private ownerships are projected to 

 continue to provide three-fourths of the hardwood 

 supplies. 



Projected Base Level Net Annual 

 Timber Growth and Mortality 



As described above, there have been substantial 

 increases in net annual growth of both softwoods and 

 hardwoods in all sections and regions and on all 

 ownerships since 1952. In total, for example, net 

 annual growth of softwood growing stock rose from 

 7.7 to 12.3 billion cubic feet, while that of hardwoods 

 climbed from 6.2 to 9.4 billion cubic feet. Net annual 

 growth of softwood sawtimber rose from 30.2 to 49.7, 

 and hardwood from 15.7 to 24.9 billion board feet. 



These trends are not expected to continue through 

 the projection period. Net annual growth of softwood 

 growing stock is projected to increase at progressively 

 slower rates to 13.5 billion cubic feet in 2010 and 

 decline slightly thereafter, to 13.2 billion cubic feet in 

 2030 (table 6.22). Net annual growth of softwood 

 sawtimber follows a similar trend, but it is still 

 increasing slowly beyond 2020 (table 6.23). 



The projected trends in net annual softwood 

 growth vary among sections and ownerships (tables 

 6.24 and 6.25). The trends for the North, South, and 

 Rocky Mountain sections are similar to the national 

 trends, although most of the decline that takes place 

 in growing stock in the last decades of the projection 

 period is in the South. Net annual softwood growth 

 in the Pacific Coast section continues to increase 

 through 2030. With respect to ownerships, net annual 

 growth increases on the National Forests, other pub- 

 He, and forest industry ownerships — the decline 

 takes place on the farmer and other private lands. 



These trends have varying causes. The increases in 

 the net annual growth on the Pacific Coast largely 

 reflect the effects of replacing the old-growth forests 

 on the National Forests and other public ownerships 



where net annual growth is low, with young forests 

 where it is high. Net annual softwood sawtimber 

 growth on the forest industry ownerships in this sec- 

 tion declines through the projection period because of 

 reductions in timber inventories. 



Inventory accumulations to the point of overstock- 

 ing are the cause of the declines in net annual growth 

 on all ownerships in the North, on public lands in the 

 South, and on most ownerships in the Rocky Moun- 

 tains. Overstocking leads to a reduced gross growth 

 and a slight increase in mortality, especially among 

 small-diameter trees. As a result, net annual growth 

 of growing stock turns down before that of saw- 

 timber. The projected reduction in net annual growth 

 in the South, nearly all on the farmer and other pri- 

 vate ownerships, is largely caused by the reversion of 

 large areas of harvested pine stands back to hard- 

 woods. Overstocking is also a contributing factor. 



The projected trends in net annual growth of hard- 

 woods are roughly the same as those for softwoods. 

 However, hardwood net annual growth peaks earlier 

 and the decline is greater. Hardwood growing stock 

 net annual growth shows a slight increase between 

 1976 and 1990 to 9.4 billion cubic feet but then drops 

 to 7.6 billion cubic feet in 2030, 19 percent below the 

 1976 level. Net annual growth of hardwood saw- 

 timber continues to increase for a longer period, but 

 after a peak of 26.6 billion board feet in 2000, it drops 

 to 24.4 billion board feet in 2030, slightly below the 

 1976 level of 24.9 billion board feet. 



The general trends of hardwoods in the sections are 

 similar to those shown by the national totals. There 

 are some differences among ownerships — most of 

 the drop occurs on the farmer and other private 

 ownerships. 



The peaking and subsequent decline in projected 

 net annual growth of hardwoods is due to overstock- 

 ing. Hardwood inventories simply cannot continue to 

 increase without eventually having an adverse impact 

 upon growth. 



In response to overstocking, softwood growing 

 stock mortality is projected to increase slightly in the 

 future, rising from 2.3 billion cubic feet in 1976 to 2.9 

 billion cubic feet in 2030. This is a reversal of the 

 downward trend in mortaUty between 1952 and 1976. 

 Hardwood growing stock mortality is projected to 

 continue its historical increase, also because of pro- 

 gressive overstocking, moving up from 1.6 billion 

 cubic feet in 1976 to 2.4 billion cubic feet in 2030. 



As a result of the influence of overstocking, a grow- 

 ing share of the projected mortality will come from 

 natural stand development. As a timber stand 

 matures and crown closure occurs, suppressed under- 

 story trees die. Because such trees are usually scat- 



245 



