Evaluating Height-Age Determination Methods for Jack Pine and Black Spruce Plantations Using Stem Analysis Data

Abstract

Tree height at a given age is important information needed to accurately estimate growth rates of trees and assess site quality of forest stands. Height growth can be estimated two ways: by direct measurement and by stem analysis. Direct measurements of height growth can be made either annually or periodically. However, a number of years are required to collect sufficient information to be useful. In contrast, stem analysis is a technique in which tree stems are cut into a number of sections and analyzed to reconstruct tree growth. Stem analysis is preferred for obtaining height‐age information, as it is both quicker and more reliable than direct measurements. Stem analysis involves measuring annual growth rings of each tree section of selected sample trees. Diameter growth and age are determined by measuring the annual ring widths and counting the number of rings, respectively. In most cases, stem sections are cut systematically across the bole, e.g., every 1.5 m (Dyer and Bailey 1987), every 1.0 m (Carmean and Lenthall 1989, Carmean et al. 2001, 2006), or at intervals equal to 10% of total tree height above breast height (Newton and Sharma 2008). Determining tree height at a given age is a challenge faced by many researchers (Carmean 1972, Fabbio et al. 1994), and as a result, a number of assumptions have been made in determining height‐age relationships. For example, Graves (1906) assumed that stems are generally sectioned just above the year’s height growth (terminal bud). He developed the first height‐age prediction algorithm by simply interpolating height growth between two consecutive stem sections to time elapsed between sections. In contrast, Carmean (1972) assumed that stems are usually sectioned in the middle of a year’s height growth when he developed a height‐age prediction method for black (Quercus velutina Lam.), white (Quercus valba L.), scarlet (Quercus coccinea Muenchh.), red (Quercus rubra L.), and chestnut (Quercus prinus L.) oaks from the central United States. Lenhart (1972) modified Carmean’s method to conservatively allocate the proportion of height growth to the growth period. Carmean’s method was further modified by Newberry (1991) to address concerns about underpredicting heights for the tops of trees.