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Weiskittel Taper Functions
Weiskittel and Li developed regional taper and volume equations for hardwood and conifer species in the northeastern United States, using Kozak's equation form (Kozak, 2004) for 27 species. MBGTools has now been coded to allow our New England clients to implement the Weiskittel taper functions. Our users in the northeast can now choose either Honer's or Weiskittel's taper functions. The following four graphs show the difference between these two taper methods on four major species:
How does the code work?
The Weiskittel taper system breaks the tree into 100 segements and the small and large end diameter inside bark (dib) is calculated for each segment. The volume of each of the 100 segments is calculated using Smalian's formula and the total cubic foot volume of the tree is calculated by summing the volumes from all segments. Total cubic foot volume of the tree, including top and stump, is calculated and stored in the CFVolTot column in CURRDATA.
What Tables in MBGTools are modified/added so that I can use the Weiskittel Taper Functions?
ADMIN table
To use the Weiskittel taper function for a stand you can either enter "WEIS" in the VolTaperType column in the ADMIN table or use the MBGTools interface database management tool to select Weiskittel in the drop down menu. The Volume region does not hold any meaning for the Weiskittel taper.
lkpKOZAKCOEFFICIENTS table
This new table stores the coefficients for calculating the taper diameters.
lkpSPPCodes table
This table should have a record for all 27 recognized tree species codes. The stump value is used for Weiskittel taper and should be populated for all species. All records in this table should have a valid species group (SppGroup) and that species group should be recorded in the lkpSPPGROUPS table.
lkpFormClass table
This table should have a record for all 27 recognized tree species codes.
lkpProduct
This table should have a record for all 27 recognized tree species codes.
Bibliography
Kozak, A. 2004. My last words on taper equations. Forest. Chron. 80: 507-514.
Li, R., Weiskittel, A.R., Kershaw Jr, J.A., Dick, A., Seymour, R.S. 2012. Regional stem taper equations for eleven conifer species in the Acadian Region of North America: Development and assessment. Northern Journal of Applied Forestry 29, 5-14.
