attention from foresters, timber owners, and other forestry 
interests. Data collected as a part of the forest survey have 
shown significant declines in the Piedmont and mountains 
of Georgia, South Carolina, North Carolina, and Virginia. 
In these areas, average annual radial growth of pine deter- 
mined from remeasurements of sample trees at breast height 
has averaged some 20 to 30 percent lower over the past 10 
years than over the previous 10. Reexamination of older 
forest-survey data on rates of tree growth indicates that de- 
clines extend back even further than the past 10 years and 
also show up in parts of the Coastal Plain in earlier remea- 
surement periods. There have also been measured declines 
in radial growth in the South Central region. 
The causes of these declines have not been determined. Pos- 
sible contributing factors include changes in stand density 
and age, drought, the exhaustion of residual fertilizers in 
the old fields and pastures that regenerated to pine, increase 
in hardwood competition, and atmospheric deposition. The 
full geographic extent of the decline is also unknown at this 
time. 
Billion cubic feet 
In the areas where the decline in growth has been measured, 
it is reflected in the yield functions used in projecting re- 
source changes. But because the causes and full extent of 
the decline are still unknown, this simulation is the only way 
to deal with the possible effects of a Southwide decline in 
radial growth. In making the simulation, it was assumed that 
the net annual growth on pine plantations, natural pine, and 
mixed pine—hardwood stands shown in the empirical yield ta- 
bles (app. tables 3.15—3.18) used in developing the base pro- 
jections would be reduced by 25 percent. 
This simulation does show major impacts on the resource 
situation in the South and the associated parts of the econ- 
omy and environment. Softwood roundwood supplies, net 
annual growth, and inventories are reduced below the base 
projections and by substantial amounts. By 2030, softwood 
inventories are 31 billion cubic feet, or 35 percent below 
the base (fig. 4.10). There are also reductions in invento- 
ries in most other important softwood timber regions. 
The drop in softwood timber inventories, and the associ- 
ated intensification in competition for the smaller supplies, 
a 
125 
100 
Base 
75 
50 Reduced timber growth 
1990 2000 
2010 2020 2030 
Figure 4.10—Projections of softwood inventories on private timberland in the South, with and without reduced timber 
growth 
PANT) 
