Growth Intercept Methods for Predicting Site Index in Red Pine Plantations in the Allegheny Plateau of Ohio

Abstract

Abstract Growth intercept (GI) techniques were evaluated for estimating site quality in red pine stands planted on old-field sites in the unglaciated Western and Central Allegheny Plateau regions of Ohio. Correlations between height growth of trees below breast height (BH) and height growth above BH were not statistically significant. Site index estimates were made using age at BH and height from BH to the growing tip. Three-year and 5-year growth beginning three internodes above the BH annual increment and 10-year growth beginning one internode above BH were more significantly correlated with height than were intercepts beginning at BH. In equations developed for predicting site index, 3-, 5-, and 10-year intercepts in combination with age accounted for 64 to 80% of the variation in tree heights. Combining thickness of the A soil horizon with GI and age statistically increased the variation accounted for in the 3- and 5-year GI equations; however, for field use, the improvement in accuracy was not sufficient to justify making the additional soil measurement. North. J. Appl. For. 7(1):27-30, March 1990.