The forest of northern California are characterized by stands of mixed 
speciesas well as mixed ages and sizes. Inventories of these stands usually
contain diameter at breast height (DBH) for each tree with only occasional 
measurements of heights and crowns. In other instances, only stand summary 
statistics or stand table data are recorded, and hence, no individual tree 
information is avialable. However, the California Conifer Timber Output 
Simulation System, CACTOS, (Wensel and others (1986), Wensel and others 
(1987), Wensel and Biging (1987)), requires that species, diameter at breast 
height (H), height-to-crown base (HCB) or live crown ratio (LCR), and per 
acre expansion factor be supplied for each tree making up the stand 
description. To obtain the most accurate representation to project with 
CACTOS, these variables should be measured for all trees.

It is evident that forest managers need a means by which these data can be 
supplemented to dorm a complete stand description comprised of complete 
individual tree records, as described above, so that individual tree growth 
and yield projections can be performed on the stands of interest for all 
different levels of data availability. This paper will discuss the operation 
of the forest stand generator, STAG, designed to meet this need. The 
estimation procedures used in STAG to : (1) fill in missing measurements of 
tree height, height to the crown base, or both; (2) generate stands from 
summary statistic and, (3) convert stand table data, numbers of trees by DBH 
classes and species, to individual tree records are described in Biging and 
others (1991), and Van Deusen (1984).

STAG is written in standard FORTRAN 77 code (ANSI, 1974) and is operational 
on IBM-PC compatibles under MS-DOS v3.3 and higher. The general structure of 
STAG is illustrated in figure 1. The components are treated in detail in 
sections which follow.


Menu Operation

STAG is a user-friendly, interactive program that makes use of menus, or 
command lists. Two-letter commands are entered from the keybpard at the 
various program prompts. Arguments to these commands can be entered to 
adjust he function of the routines invoked from their initial, default 
conditions. The command list can be displayed by typing pc, for print 
commands, at any of the program prompts. Only the commands available to the 
user within each routine are displayed. All of the commands are described in 
detail in section IV, Program Commands.

Stand Description

The stand description that STAG reads and/or creates has two types of records-
header and tree records. The header records contain the stand label, number 
of tree records, elevation, and site and age of each species present. The 
complete individual tree record required by CACTOS includes the following 
five items:

    (1) a two digit species code
    (2) diameter at breast height in inches (DBH)
    (3) total height in feet
    (4) live crown ratio
    (5) number of trees per acre represented by the tree record

This information comprises the tree list representing a stand that is 
created on output from STAG and which CACTOS uses for simulation. Since 
these data are frequently drawn from a sample, it is important that they be 
carefully examined to see that really do represent the stand of interest.

The tree records in a stand description file may be incomplete, and STAG can 
fill in missing heights and crown ratios for these records. Alternatively a 
description may be of a stand table, where the entries are species, diameter 
class (diameter class intervals must be 2 inches or less), and number of 
trees per acre in that diameter class for a given species. Stand description 
files can be entered outside of STAG or CACTOS using either a standard text 
editor or Entry, the CACTOS System stand description entry program 
(Meerschaert and Wensel, 1987)