Shortleaf Pine (Pinus echinata) Site Index Equation for the Cumberland Plateau, USA

Shortleaf pine site index on the Cumberland Plateau is one of the least studied silvics of the species. To obtain site index information, practitioners must use site index curves from outside the region. This research proposes a novel approach to using US Forest Service, Forest Inventory and Analysis data to develop a shortleaf pine site index equation specific to the Plateau. Shortleaf pine site trees (n = 410) were grown forward or backward until base age of 50 years, using site specific, mixed-model parameters. Over thirty height models were then fit using traditional methods and the algebraic difference approach (ADA). Fit and cross-validation statistics, along with examinations of model behavior, showed that a derivation of the Lundqvist-Korf model provided the best estimates. The model was rearranged to directly estimate site index, and a traditional site index graph is provided. Site index estimates had average validation results nearly four times better than the currently recommended site index curve developed off the Plateau. Forest practitioners now have access to improved site index estimation for restoring and managing shortleaf pine on the Cumberland Plateau. Study Implications: With the development of a locally calibrated site index equation, forest practitioners now have access to substantially improved site quality estimates for use during forest management planning and research. Restoration efforts will benefit from better forecasts of stand development and resulting tailored management based on site quality. In addition, others may use the study's novel approach to create site index equations for other species from existing and traditional forest inventories.