Yield Relationships in Unthinned Loblolly Pine Plantations on Cutover, Site-Prepared Lands

Abstract

Abstract Data were collected in unthinned loblolly pine (Pinus taeda) plantations on cutover, site-prepared lands across much of the southern United States. Initial measurement data from these permanent plots were used to (1) develop regression relationships between yield of the planted loblolly pine and measurements of the planted pine and competing vegetation, and (2) assess relationships between yield and site preparation methods and physiographic regions (Coastal Plain and Piedmont). These analyses showed that yield of the planted pine component could be predicted adequately from age, average height of dominant and codominant trees, and number of surviving planted trees per unit area. Measurements on the competing vegetation did not significantly reduce the error sum of squares after accounting for the planted-pine variables. An analysis of covariance showed that mean yields (after adjusting for the effects of plantation age, site index, and number of surviving trees) were not significantly different for site preparation classes or physiographic regions. Further analyses showed that survival relationships were similar for the physiographic regions and site preparation classes included. Although the height-age relationships for anamorphic site index curve construction were significantly different for the Coastal Plain and Piedmont, there were no significant differences between site preparation classes within the regions.1