Evaluation of Two Eastern White Pine Site Index Equations at Biltmore Estate, North Carolina
The accuracy of two white pine (Pinus strobus L.) polymorphic site index equations was compared with field data from three plots in a loo-year-old stand at Biltmore Estate, Asheville, NC. One equation was developed from New Hampshire data and the other from Southern Appalachian data. Tree height has been measured periodically on those plots between stand age 34 and 72 years. At 50 years, site index ranged from 54 to 73 feet (ft). Absolute deviations of actual from estimated site index averaged 2.5 ft for the Southern Appalachian equation and 2.7 ft for the New Hampshire equation. Site index estimates ofthe New Hampshire model were highly correlated (r = 0.92) with estimates of the Southern Appalachian model. Our evaluation indicates that the New Hampshire equation, which has desirable properties lacking in the Southern Appalachian equation, may be applicable on low- to moderate-quality sites beyond the area in which it was to be used. We suggest that a regional approach to site index development for white pine may be appropriate.