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5.4 Timberland distribution, composition and stand structure

The South's physiography largely determines the distribution and composition of its forests. In general, hardwoods are dominant in the Mountains and much of the Piedmont Plateau, and softwoods predominate in the Southern Coastal Plains. The composition and structure of southern timberlands can be described by the distribution of forest types, stand size and age, and stand origin. Forest types are based on the tree species forming a plurality of live-tree stocking. Stand size is based on the diameter distribution of all live trees in a stand, while stand age represents the age of the dominant and codominant trees in the stand. Stand origin identifies a stand as having been established through natural regeneration, or through planting or seeding by humans.


5.4.1 Distribution of timberland area by forest type

Changes over the past 50 years have altered the extent and distribution of hardwood and softwood forest types throughout the South. Overall, area in hardwoods and oak-pine has been increasing and the area in softwoods has been decreasing. In 1953, upland and lowland hardwood forest types combined accounted for 46 percent of the region's timberland, or 94 million acres (Figure 9 and Table 5). In 1999, hardwood forest types combined accounted for 52 percent of the South's 201 million acres of timberland. Oak-pine stands occupied 12 percent of the area in 1953, and 15 percent in 1999. Softwood forest types--principally longleaf-slash pine and loblolly-shortleaf pine--occupied 39 percent of the South's timberland area in 1953, but have accounted for less than one-third since 1982.


Most notable among the trends in softwood forest types is the continued decline in the area of longleaf-slash pine types. Longleaf pine is estimated at one time to have occupied 60 million acres in the Coastal Plain and Piedmont areas of the Atlantic Coast States (McWilliams and others 1997). By 1953, the combined area of longleaf-slash pine forest types had declined to 27 million acres. In 1999, area of longleaf-slash pine had been reduced to 13 million acres. Two-thirds of the acres of longleaf-slash pine remaining in 1999 were in Florida and Georgia (Table 6).


Loblolly-shortleaf pine forests have accounted for about one-fourth of the South's timberland area since 1953 (Figure 9), despite a steady decline in actual acreage; from 52 million acres to a low of 46 million acres in 1989 (Table 5). The area of loblolly-shortleaf increased to 50 million acres by 1999, and still accounted for one quarter of the South's timberland area.


The white-red-jack pine forest-type group occupied 688,000 acres in 1999. This national standard type-group is somewhat of a misnomer in the South. While white pine is a component of red and jack pine forest types in more northerly climes, in the South this forest-type group is composed almost entirely of white pine forest types.


Upland hardwoods--oak-hickory and maple-beech-birch forest types--accounted for 37 percent of the timberland area in 1999. The area of oak-hickory increased steadily between 1953 and 1999, from 55 million acres to 74 million acres (Table 5). Oak-hickory timberland increased in 9 of the 13 Southern States since 1982, including the addition of 2 million acres in Alabama (Table 6). Maple-beech-birch forest types increased from 750,000 acres to 1 million acres between 1953 and 1999.


Lowland hardwoods, which in the past have accounted for as much as 19 percent of southern timberlands, occupied 15 percent of the area of timberland in 1999. Acres of oak-gum-cypress and elm-ash-cottonwood, which comprise the lowland hardwood group, declined from 39 million acres to 31 million acres over the past 46 years.


5.4.2 Distribution of timberland by stand size

Timberland acres with less than 16.7 percent stocking are classed as nonstocked.


The distribution of timberland by stand size has changed considerably since 1953 (Figure 10). Acres of sawtimber and sapling-seedling stands have increased, while acres of poletimber stands and nonstocked acres decreased. Poletimber stands dominated in 1953, accounting for 41 percent of the acres of timberland (Smith and others 2001). Less than one-third of the stands were sawtimber, roughly one-fifth were classified as sapling-seedling stands, and 8 percent were nonstocked. A decade later, sawtimber and poletimber stands each occupied 35 percent of the South's timberland area. In 1963, stands with a plurality of stocking in saplings and seedlings accounted for nearly one-fourth of the area. These general trends continued, and by 1999 45 percent of the timberland area was in sawtimber stands; one quarter was in poletimber stands; 29 percent was in sapling and seedling stands. Only 1 percent was nonstocked in 1999.


The trends in stand size differ for hardwoods and softwoods (Table 7). Since 1982, the upward trend in the total area of sawtimber has been driven by increases in hardwood sawtimber. Hardwood sawtimber rose 17 percent to 65 million acres in 1999. Every State in the South, except South Carolina and Texas, had more hardwood sawtimber stands in 1999 than in 1982. Part of the reason for the increase is basic economics. Hardwood species are generally less desirable for timber products until they reach sawtimber size, and many hardwood stands are in remote mountainous areas, which are more difficult to log (TMBR-1). As a result, more trees are left to grow into the larger diameter classes.


The area of softwood sawtimber has declined 8 percent since 1982. Florida, Georgia, Mississippi, and Texas have lost softwood sawtimber in successive inventories, and Alabama, Louisiana, and South Carolina have fewer acres in this class now than in 1982. The remaining five States have slightly more acres of sawtimber than a decade ago. The decline in sawtimber--softwood and hardwood--in South Carolina between 1989 and 1999 was due at least in part to damage from Hurricane Hugo in 1989.


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