Download PEM Predictive Ecosystem Mapping User's Guide

Predictive Ecosystem Mapping User’s Guide
PEM Applications
Page S4-2
landbase, forest inventory, timber growth and yield, and management
practices and parameters. PEM information may be used in preparing
the first three types of data (see Section 4.1.4).
4.1.3 Modeling Timber Supply
Timber supply analyses always follow the same basic procedure
regardless of which model is used. After the initial gathering of data and
documentation of assumptions, the analysis proceeds as shown in
Table 4-1.
Table 4-1
Steps in timber supply analysis to support AAC
determination
Step 1
Categorize the
landbase
The productive forest in a management unit is separated into the
portion that is available for harvesting (the timber harvesting
landbase) and the portion that is unavailable or inappropriate for
timber production.
Step 2
Assign
management
zones
If management practices are not the same everywhere in the
management unit, the unit is divided into zones in which different
management objectives, requirements, and practices can be
modeled (e.g., watersheds, wildlife habitat areas, recreation areas).
Step 3
Classify the
forest inventory
Forest stands are classified into units that are suitable for projecting
the yields of timber. These classes, which are referred to as analysis
units, are usually based on leading tree species and site productivity
(e.g., spruce-leading stands with site index greater than 18 m).
Step 4
Project
stand yields
Stand yield is projected for each management regime to be applied
to each analysis unit. These projections are represented as timber
yield tables that show stand characteristics at different ages (e.g.,
timber volume per hectare, average stem diameter).
Step 5
Identify
management
activities and
requirements
Current management activities, including those that enhance timber
production (e.g., planting, thinning), and those that maintain or
enhance other forest values (e.g., wildlife habitat, visual quality), are
identified. Management requirements and the area to which they
apply are identified.
Step 6
Model the
timber supply
base case
In each decade simulated, the model harvests available timber up to
the target volume, and then "grows" the forest. The area available
for harvesting each decade is limited by management requirements
such as forest cover constraints and minimum harvest ages.
Step 7
Sensitivity
analysis
Sensitivity analysis is carried out to evaluate sources of uncertainty
in the data and the management assumptions.
Step 8
Synthesis of
results
The TSR Timber Supply Analysis Report summarizes the information
that was used in the analysis, states the base case harvest forecast,
and synthesizes the results of the sensitivity analyses.
March 28, 2005