Adjusting site index and age to account for genetic effects in yield equations for loblolly pine

Abstract

Nine combinations of site index curves and age adjustments methods were evaluated for incorporating genetic effects for open-pollinated loblolly pine (Pinus taeda L.) families. An explicit yield system consisting of dominant height, basal area, and merchantable green weight functions was used to compare the accuracy of predictions associated with type of adjustment. Site index was adjusted by including height-age curves developed for the check family, all improved families combined, and for specific families. Age was adjusted by using a variant of the Pienaar and Rheney (1995) function. Age adjustments included none, all improved families combined, and for specific families. The best results were obtained by using height-age curves for all improved families combined and a family-specific age adjustment function. These results suggest that adjusting either site index alone or age alone is not sufficient for predicting the yield of genetically improved loblolly pine families planted in single-family blocks.

Parent Publication

• Proceedings of the 14th biennial southern silvicultural research conference

Citation

Knowe, Steven A.; Foster, G. Sam. 2010. Adjusting site index and age to account for genetic effects in yield equations for loblolly pine. In: Stanturf, John A., ed. 2010. Proceedings of the 14th biennial southern silvicultural research conference. Gen. Tech. Rep. SRS–121. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 383-387.