Variable Density Yield Projection
Volume 1 - VDYP 7 Overview Draft

10 March 2007

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This manual provides general information about VDYP7 application and describes how to use this documentation set. The VDYP7 core programs, common to each interface, are described within this overview.

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This manual describes how to use this interface to generate yields for adjustment, import adjustment factors and project an adjusted or unadjusted inventory.

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As VDYP7 uses basal area instead of crown closure for density calculations, volume predictions should more closely approximate actual changes in volume across the density range. Projected volume trends will also differ between the two models. With VDYP7, the volume trend is affected by changes to Lorey height and BA over time. With VDYP6, crown closure is held static over the projection and volume increase depends strongly on height growth. Thus VDYP7 volume projections are more likely to decrease in the long term since the Lorey height of stands tend to flatten and the BA may also decline in old stands. The new stand-level decay model used in VDYP7 tends to increase the deduction for decay as stands get older to better emulate actual conditions.

As part of the VDYP7 implementation process, reports which compare VDYP7 volume predictions to VDYP6 are soon to be released:

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