movals, and supplies are presented in separate tables for 
ownership and management type categories. 
All historical data were derived from State inventories con- 
ducted at various dates from the 1940’s to the present as a 
part of the Forest Survey. Simple interpolation and extra- 
polation were used to adjust the data to common years, in 
effect updating or backdating the inventories. Forest Ser- 
vice planting records and long-range ownership trends were 
used to provide cross tabulations by owner and forest 
classes for some of the earlier surveys. Estimates for all 
States for 1985 are strongly influenced by trends in the 
most recent State surveys in the South, and midcycle or in- 
terim surveys where available. The Timber Resource Inven- 
tory Model projections began with inventory data from the 
most recent State survey. The average date of these sur- 
veys was about 1980. The first projection period, 1980-85, 
was used to update and calibrate the Timber Resource In- 
ventory Model input data with the historical data for 1985. 
Projection results are reported from 1990 to 2030. 
State-Level Projections 
The Southern Area Model yields State-level area projections 
because sub-State regions are used as the basic model 
units. The Timber Assessment Market Model operates 
regionally (Southeast and South Central) and the Timber Re- 
source Inventory Model, which is capable of operating at 
the State level, was also run regionally. Thus, the basic pro- 
jections of timber resource changes were made regionally. 
The projections of changes in timber 
resources in this study are based on a 
comprehensive data base collected by the 
USDA Forest Service as a part of a 
continuing inventory of forest resources—the 
“Forest Survey.”’ 
86 
The State estimates were developed using the State Alloca- 
tion of Regional Inventory Model (SARI). 
This State system maintains consistency with the regional 
systems by estimating State shares of regional growth, 
removals, and inventory change due to area change. It uses 
estimates of regional growth and removals by ownership/ 
management type from the regional model, State acreage 
projections, and historical State data to make State inven- 
tory projections. A State’s growth is estimated by (1) its his- 
toric growth per acre relative to the other States in the 
region, (2) its projected acreage of timberland, (3) projected 
timber inventory, and (4) site quality. 
The latest Forest Service survey information in each State 
is used to estimate growth per acre for each State/owner/ 
management type combination (Abt 1987). Some of the fac- 
tors affecting State growth (e.g., management intensity and 
stocking) are accounted for by recognizing differences be- 
tween owners (forest industry vs. individual) and manage- 
ment types (pine plantation vs. natural pine). Within an 
owner/management type class, the growth differentials ac- 
count for differences in site quality, stocking, and species 
mix. Over the projection period, growth differentials are 
adjusted to reflect projected differences in inventory per acre 
and average site quality between States. 
Total region removals are allocated to States in a five-step 
procedure: 
(1) Industrial production was shifted between States to main- 
tain historical relative stumpage price differences between 
States; 
(2) Harvest was allocated to States based on ownership mix, 
changes in inventory, and proportion of regional industrial 
production; 
(3) State harvest was allocated to owners based on changes 
in inventory by owner and change in State industrial 
production; 
(4) Harvest by ownership within States was adjusted propor- 
tionately to be consistent with total regional harvest by own- 
ership and proportion of regional harvest by the State; and 
(5) State harvest by ownership was allocated to manage- 
ment types based on inventory and historical removal pro- 
portions by management type. 
