WOODLOT for Windows 2.1 - Reference Manual

Appendix 6 - VDYP or TIPSY (Source: adapted from WinTIPSY 1.3 Help File, BC MOF, Resources Inventory Branch) VDYP The Variable Density Yield Prediction (VDYP) system was developed by Inventory Branch using randomly located plots which cover the full range of conditions found in our forest land base. Consequently, VDYP projects the average yield of naturally regenerated stands which have not been treated. The empirical yields from VDYP will invariably be lower than the potential yields given by TIPSY. Yields from VDYP can be adjusted to approximate local actual volumes by using the Volume Adjustment Factor (VAF). VDYP should be used for determining yields on naturally occurring unmanaged stands. TIPSY The Table Interpolation Program for Stand Yields (TIPSY) is a program that utilizes yield tables derived for managed stands. These stands have had treatments to bring them to a full growing state within a normal time, for stands spaced at 4-6 m, or stands that have been previously harvested. TASS generates the yield tables in TIPSY's database. TASS, the Tree and Stand Simulator, is a computer model that simulates the growth of individual trees and stands in three dimensions. The crowns of individual trees expand and contract asymmetrically as branch extension responds to internal growth processes, physical restrictions imposed by the crowns of competitors, environmental factors and silvicultural practices. The crowns add a shell of foliage each year that benefits the trees in diminishing amounts for several years. The volume increment produced by the foliage is distributed over the bole annually and accumulated to provide tree and stand statistics. TASS is based on growth trends observed in fully stocked, near ideal, research plots growing in a relatively pest-free environment. The yields will be very close to the potential of a specific site, species and management regime. TIPSY yields are adjusted to approximate operational conditions by using Operational Adjustment Factors (OAFs). Refer to Mitchell and Cameron (1985) and Mitchell (1975) for more information on TASS. Research Branch maintains the system. TIPSY should be used for managed stands. Default OAFs should be used unless you have better information.

by Enfor Consultants Ltd. Last Updated March 1999