Research Report No. 29, Site Index Equations for Loblolly and Slash Pine Plantations in East Texas, Update: 1994

In 1986, equations to estimate site index in loblolly and slash pine plantations in East Texas were published (Lenhart et al. 1986). Subsequently, updated site index prediction equations were published in 1993 (Vaughn et al. 1993). Both sets of equations were developed using data collected from East Texas Pine Plantation Research Project (ETPPRP) permanent plots distributed throughout East Texas. The site index prediction equations were designed to estimate tree height 25 years from planting, ie., index age = 25 years. Data for the 1986 and 1993 site index prediction equations were from measurements of the ETPPRP permanent plots during 19182-1984 (a 3-year period) and 1982-1992 (an 11-year period), respectively. In this 1994 update, new versions of site index prediction equations are presented for loblolly and slash pine plantations in East Texas based on information from repeated measurements of the ETPPRP permanent plots during 1982-1 993. During this 12-year period, the ETPPRP plots have been measured four times. As a result, the new loblolly pine site Index equation is based on the analysis of 653 ageheight pairs, and the new slash pine site index prediction equation is derived from 296 age-height pairs. The equations in this 1994 update should quantify the productivity of East Texas loblolly and slash pine plantations in a more accurate and reliable manner than the two previous sets of equations