Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University | Faculty of Forestry, College of Agriculture, Chonbuk National University
Laboratory of Forest Planning, Division of Forest Management, Dep. of Forests and Forest Product Sciences, Faculty of Agriculture, Kyushu University | Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University
九州大学農学部森林機能制御学
Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University | Faculty of Forestry, College of Agriculture, Chonbuk National University
Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University | Faculty of Forestry, College of Agriculture, Chonbuk National University
Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University | Faculty of Forestry, College of Agriculture, Chonbuk National University
Department of Forest Resources, College of Agriculture, Sunchon National University | Department of Forestry, Chonnam National University | Faculty of Forestry, College of Agriculture, Chonbuk National University
Douglag-fir (pseudotsuga menziesii Mirb. Franco) ranks as the second most important plantation tree species after radiata pine in New Zealand. Site index equations to derive site index curves for Douglas-fir plantations have been developed based on mid-term repeated measurment data sets, and then site index curve (base age 40 years) was developed. The function was developed by algebraic difference eqation method. Of the projection functions tested, Gompertz polymorphic equation showed the higher precision of the fitting. Ninety-five percent of the observations used to fit model could be predicted with ±1.7m of the actual values. Polymomphic family of site index curves, hence, which reflect different shapes for the different site index classes, were derived from the Gompertz equation. This function represents measurement times T_1 and T_2 as T_2-T_1, while the Hossfeld and Schumacher functions, which had the second lower MSE values, encapsulate T_1 and T_2 as T_2/T_1. The applicabaility of the Gompertz function, therefore, was enhanced with study data set that contain medium measurement cycles.