140 



TIMBER RESOURCES FOR AMERICA'S FUTURE 



Cull trees take up gro\ving space and thus re- 

 duce the productivity of the forest land. Because 

 rotten culls contain proportionately less sound 

 wood than growing stock trees, their net volumes 

 understate the growing space that cull trees oc- 

 cupy. For example, in the Southeast and West 

 Gulf regions, cull trees account for more than one- 

 fifth of the total basal area of all trees in the 6-inch 

 and larger diameter classes. About ever}" fifth 

 tree of sawtimber size in the Central Region is a 

 cull. In New England, where hardwood culls 

 make up 17 percent of live-tree net volume, they 

 represent more than 22 percent of the gross 

 volume. 



The inventory of cull hardwood in the East has 

 been gradually changing. In some regions, stand 

 quality has been raised by the expanding use of 

 low-quality hardwood trees for pulp-making. In 

 the Southeast, where successive estimates are 

 available, stand deterioration seems to be con- 

 tinuing. Here, the original surveys found 77 per- 

 cent of the total sound hardwood volume in grow- 

 ing stock trees and 23 percent in cull trees. By 

 1953 the sound-wood proportion in growing stock 

 trees had dropped to 71 percent and the cull-tree 

 percentage had climbed to 29. Heavy cutting of 

 the better trees had reduced the level of growing 

 stock. Left to grow, the cull trees increased in 

 volume. 



Compared to hardwood, cull trees of softwood 

 species occupy a small proportion of softwood 

 stands. In the West, 3 percent of the total sound 

 volume of softwood is in cull trees; in the East, 

 cull trees account for 5 percent of the sound soft- 

 wood volume. Only in Coastal Alaska are the 

 softwood forests characterized by a large volume 

 in cull trees — some 22 percent of the total sound 

 volume in that region. However, in all regions 

 the sound wood volume of softwood growing stock 

 includes much material that is unsuited for saw- 

 log use because of small size or poor form. 



Better Quality Species Diminishing 



Composition of timber volume by species and 

 distribution of area by forest types are not exact 

 criteria of stand quality, but for most end uses 

 some species and types are generally considered 

 more desirable than others. The available evi- 

 dence shows that the more aggressive but less 

 desirable species are tending to displace preferred 

 species in both the East and the West. 



In the East, many of the young-growth forest 

 types are not especially stable. As a result of 

 disturbance due to cutting, fire, grazing, or insect 

 and disease infestations, some species are favored 

 and the type tends to change. Even without dis- 

 turbance of any kind, most young-growth types 

 tend to change with time as short-lived species die 

 out and as conditions for regeneration are altered. 



For example, in the South the leading softwood 

 type, lobloUy-shortleaf pine, has been expanding 

 at the expense of the longleaf-slash pine. In turn, 

 the more aggressive hardwood types, as a result 

 of continued fire protection, are replacing lobloUy- 

 shortleaf pine in some areas. 



Because of fire, cutting, hardwood competition, 

 and lack of seed sources, white pine, once the 

 prominent forest type in the Lake States, has 

 been reduced to about a million acres. The aspen- 

 birch type has come in instead. In the young- 

 growth spruce-fh" stands of the Northeast, hard- 

 woods tend to supplant softwood. The net effect 

 of these shifts has been a gradual reduction in the 

 eastern softwood acreage and an increase in hard- 

 wood acreage. The shifts will be even more 

 noticeable in the future as young growth matures. 

 The relationships between species composition 

 and timber quality are also apparent in the East. 

 Wherever resurveys of large forest areas have 

 been made they have shown that the proportion 

 of better qualit}' species in the sawtimber volume 

 inventory has generaUj^ decreased, while the pro- 

 portion of poorer quality species has increased. 

 They bear out the general observation that cut- 

 tings that are concentrated on preferred species or 

 high-quality trees often lower stand quality, be- 

 cause more of the area is taken over by the less 

 desirable species that remain, or sprout, or seed-in. 

 Type and species changes are also taking place 

 in the West. Lodgepole pine has formed dense 

 stands following fire in some other softwood types. 

 Through cutting of white pine and not the asso- 

 ciated species, other softwoods now predominate on 

 many former white pine areas in the Northern 

 Rocky Mountain Region. Because of blister rust, 

 some white pine stands have also been giving way 

 to fir and larch. In local areas in the Pacific 

 Northwest, as the Douglas-fir type passes maturity 

 western hemlock invades and appears in great 

 abundance. Ponderosa pine, a preferred species, 

 has lost ground to white fir, which in the West is 

 exceptionally aggi-essive following logging. 



These are only a few examples of changes in 

 forest types and species composition that could be 

 cited to show declines in stand quality and losses of 

 potential productivity of the forest site. Changes 

 that indicate improvement in stand quality are 

 less numerous — probably because most such 

 changes take place very slowly. Although it is 

 difficult to appraise the magnitude of such changes, 

 it is apparent in both the East and the West that 

 the more aggressive but less desirable species are 

 tending to displace preferred species. 



Trends in Timber Volume 



From time to time since 1895, estimates have 

 been made of the volume of standing timber in 

 the United States. Occasionally, a series of 

 estimates, such as the following, have been pre- 



