Southern Research Station

Title: Validation of Volume and Taper Equations For Loblolly Shortleaf and Slash Pine

Author: Tiarks, Allan E.; Baldwin, V. Clark, Jr.

Date: 1999

Source: Paper presented at the Tenth Biennial Southern Silvicultural Research Conference, Shreveport, LA, February 16-16,1999.

Description: Inside-bark diameter measurements at 6.64 intervals of 137 loblolly, 52 shortleaf, and 64 slash pines were used to calculate the actual volume and taper of each species for comparison with volumes and tapers predicted from published equations. The loblolly pine were cut in Texas (TX) and Louisiana (LA) while the shortleaf was sampled only in TX. The slash pine were sampled in Mississippi (MS). The models had been developed using trees that had the same diameter and height distributions as the validation data; however, the validation trees were generally older. For loblolly and slash pine, the volume equations over-predicted the average volume by 1.5 and 3.7 ft³/tree, respactlvaly, or about 5 to 10 percent of tree volume. The taper equation for loblolly was adequate, but the slash pine taper equation did not fit the data well. There is no appropriate volume or taper model for shortleaf pine. However, the loblolly equations predicted both volume and taper of the shortleaf pine data as well as or better than they did for the loblolly data. The loblolly and slash pine equations can be used with confidence-about half of the errors appear to be random, indicating that the best equations will have an error of about 1.5 ft³/tree regardless of tree size. Most prediction ermrs occurred In larger trees, indicating that some improvement could be made in taper-volume models by adding age as a variable. Specks seems to be less important, and future modeling efforts should evaluate combined species equations.

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Citation

Tiarks, Allan E.; Baldwin, V. Clark, Jr.  1999.  Validation of Volume and Taper Equations For Loblolly Shortleaf and Slash Pine.   Paper presented at the Tenth Biennial Southern Silvicultural Research Conference, Shreveport, LA, February 16-16,1999.