Volume and taper equations for Sitka spruce (Picea sitchensis (Bong.) Carr.), Norway spruce (Picea abies (L.) Karst.) and White spruce (Picea glauca (Moench) Voss) in Iceland

摘要: The aim of this study was to evaluate different types volume and taper equations that can be used predict single-tree stem diameter at any given height along the tree for plantation grown Sitka spruce (Picea sitchensis (Bong.) Carr.), Norway abies (L.) Karst) White glauca (Mounch) Voss) in Iceland. A number published were tested modified total volumes over bark but three logarithmic taken more in-depth analysis. Three tested. Two variable-exponent (Kozak 1997, Kozak 2004) one exponential equation described by Biging (1984). Data from a 617 sample trees study, collected stands various parts country present growing soil cover most site conditions suitable forestry To fit regression model an ordinary least-squares (OLS) method used. Because construction requires longitudinal data or multiple measurements on individual trees, violates assumption independence between observations, mixed effects approach within autocorrelation. Volume [5] which has breast (D), (H) (H-1.3) as independent variables gave best results based validation statistics are all species. In prediction version (1984) is showed some bias predicting small same noticed developed (1997). (2004) seems flexible well bigger should give among equations.