How Spatial Woodstock updates inventory outputs and yields

Spatial Woodstock allows you to create maps of dynamic attributes—inventory outputs, yield attributes, and forest strata (development type classes in Woodstock parlance)—both today and into the future. This enables you to portray the impacts of management strategies on forest conditions spatially over the projection period.

However, inventory outputs behave differently than the other dynamic attributes and it is important to understand this difference when analyzing maps.

The purpose of this tech tip is describe how Spatial Woodstock projects dynamic attributes on maps. Spatial attribute projections are accomplished using the time selector window, which contains a slider bar and edit box for
selecting the current planning period. When you open the time selector, Spatial Woodstock adds dynamic attributes to the shapefile and the current planning period is set to 0, which represents present-day forest conditions (or those conditions present in the shapefile/Areas section). As you increment the current planning period, Spatial Woodstock updates dynamic attributes to represent management-induced change (actions and transitions) and growth (ageing).

There are two rules that you must be aware of when performing spatial time projections and interperting maps of dynamic attributes:

1) Yields, thematic attributes and ages represent conditions at the beginning of the period, before actions, transitions and growth in that period.
2) Inventory outputs represent conditions at the end of the planning period, after actions, transition and growth in that period.

This not only adheres to the underlying rationale used in the planning system to calculate outputs, it also ensures that output maps correspond with the outputs values in Woodstock.

The differences here are a function of the timing of calculations relative to growth in a period (see Tech tip: Understanding Outputs: Timing of output calculations in Woodstock).

For example, to map habitat in period 10 using an inventory output, compile the model, display the habitat output in the maps view and advance the time selector to period 10.

To map habitat in period 10 using a yield table value, compile the model, display the habitat yield in the maps view and advance the time selector to period 11.

So what is the takeaway message? To map forest conditions in a particular planning period using an inventory output, display the output in the maps view and advance the time selector to the planning period of interest. To map forest conditions using yields or thematic attributes, display the yield in the maps view and advance the time selector to one period beyond the planning period of interest (planning period of interest plus one).