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5.12 Southern forest ecosystems: Province ecological units

Framers of the Southern Forest Resource Assessment agreed to report results for ecological units as well as for more traditional units. The three higher levels of ecological units consist of Domain, Division, and Province (McNab and Avers 1994). The Province, which represents the regional scale, is the level at which FIA data are aggregated, analyzed, and discussed in this Chapter.

5.12.1 Distribution of timberland by Province and forest type

Portions of 11 Ecological Provinces occur in the South (Figure 35). FIA data are organized by county, so it was not possible to follow Province boundaries exactly. Instead, each county was mapped into the Province that encompassed the greater portion of the county area.

The distribution of the South's timberland area by forest type and Province is shown in Figure 36 and Table 29. The largest forested Province in the South is the Southeastern Mixed Forest, which has 121 million acres of land, including 80 million acres of timberland. The Province extends from northern Virginia to eastern Texas and contains acreage of every major forest type in the South except spruce-fir, which is limited to the Central Appalachian Province. Oak-hickory forest types are the most abundant hardwoods and occupy 27 million acres or 34 percent of the timberland area in the Southeast Mixed Province. Nearly 1 out of every 3 acres of oak-hickory in the South are in this ecological unit. This Province also contains 28 million acres of loblolly-shortleaf pine--56 percent of the area of these forest types in the Southern region.

The South's Atlantic and Gulf Coasts comprise the Outer Coast Mixed Forest Province. Stretching from coastal Virginia to southern Louisiana and extreme eastern Texas, the 101 million acres in this ecological unit support 59 million acres of timberland. Forty-seven percent of the timberland in the Outer Coast Mixed unit is in pine types, including 13 million acres--92 percent--of the longleaf and slash pine forests found in the South. This unit also encompasses 15 million acres of loblolly-shortleaf pine. Primary hardwood forest types are oak, gum, and cypress, which occupy 14 million acres, nearly half of the oak-gum-cypress forests in the region.

The largest of the South's three mountain provinces is the Central Appalachian ecological unit with 23 million acres. As the name implies, this Province includes the Appalachian Mountains of northern Virginia south to northeast Georgia. Within its boundaries are 15 million acres of timberland, including all the primary forest types in the South except longleaf and slash pines. Most of the timberland in the Central Appalachian Province--10 million acres--is occupied by the oak-hickory type. Oak-pine forests account for 2 million acres, and maple-beech-birch stands occupy another 374,000 acres. Less than 10 percentof the area is in loblolly and shortleaf pine forest types. The white-red-jack forest type group occupy 543,000 acres in this Province. Although the type includes red and jack pines, white pine is the predominant species in the South.

5.12.2 Planted and natural pine and oak-pine stands by Province

In 1999, planted pine/oak-pine stands occupied 34 million acres throughout the South. Some 31 million acres were in the Southeast and Outer Coast Mixed Provinces (Figure 37 and Table 30). Planted stands account for nearly one-quarter of the timberland area in the two Provinces combined. Natural pine/oak-pine acres still outnumber the planted stands in these units, occupying 48 million acres. In the Southeast Mixed Province the ratio of natural to planted pine/oak-pine is 2-to-1. This is not the case for the Outer Coast, where there are just 1.1 acres of natural pine/oak-pine for every planted acre. Hardwoods occupy the remaining area in both units--59 million acres.

Planted pine/oak-pine stands are a minor component in the other Provinces, except for the Ouachita Mixed unit, where they occupy 1 million of the 4 million acres of timberland. The 3 million acres that make up the rest of the Province are split evenly between natural pine/oak-pine, and hardwood forest types.

5.12.3 Distribution of timberland by Province and ownership

Timberland ownership by Ecological Province is shown in Figure 38 and Table 31. As the map illustrates, timberland owned by private individuals is well represented in each of the 11 Provinces. Individuals control more than half the timberland acres in all but two Provinces, and own as much as 82 percent of the Eastern Broadleaf Forest (Continental) unit, and 85 percent of the Everglades Province. The two units where private individuals own less than half of the timberland are the Outer Coast Mixed Forest Province--48 percent --and the Ouachita Mixed Forest Province--30 percent.

Forest industry and corporate ownerships are concentrated in the Outer Coast Mixed and Southeast Mixed Provinces, as are national forest and other public timberlands. Industry ownership in the two units combined totals 34 million acres, which is 86 percent of all industry timberland in the South. Seventy percent of all corporate timberland--13 million acres--is in these Provinces.

National forest timberland in the Outer Coast and Southeast Mixed Provinces combined, amounts to 5 million acres, or 47 percent of the national forest timberland in the South. Another 28 percent, or 3 million acres of national forest land is in the Central Appalachian Province. This Province contains the George Washington and Jefferson National Forests in Virginia, and major portions of the Pisgah and Nantahala National Forests in North Carolina. Corporations control about 2 million acres in the Central Appalachian Province.

5.12.4 Live tree volume on timberland by Province

Hardwood live tree volume density is shown in Figure 39. This map illustrates that the Appalachian, Smokey, and Ozark Mountain Ranges have the highest hardwood densities in the South. Conversely, the Mississippi Delta, south Florida everglades, and the extreme western edge of the survey range have little hardwood volume. These areas also have little softwood volume (Figure 40). Additionally, the Eastern Broadleaf Forest (Continental) and parts of the Appalachian Mountain units have low softwood densities. Softwood volume also is low in the Blackland Prairie, which runs through Alabama and Mississippi. The highest softwood densities are in central Louisiana and southern Arkansas, as well as the northwestern edge of the Outer Coast Mixed Province.

Investigating total volume by province reveals the relationship between area and volume. The Southern Mixed and Outer Coast Mixed Provinces contain a majority of timberland area and volume. The Southern Mixed Province has 40 percent of the timberland area and 41 percent of the total growing-stock volume (Table 32).

5.12.5 Average net annual growth and removals of live timber by Province

The Southeast Mixed Province dominates the South in net annual growth and removals of live trees (Table 33). This Province, which accounts for 40 percent of the total timberland area in the South, is responsible for 50 percent of the South's average net annual growth and 59 percent of its average net annual removals. The Southeast Mixed and Outer Coast Mixed Provinces are the only two in which softwood removals exceed growth. With the exception of the Everglades, growth exceeds or equals removals for both softwood and hardwood species in all other Provinces.