SITE INDEX OF PAPER BIRCH IN ALASKA

Abstract

Height growth patterns and site index were developed using stem analysis of four dominant or codominant trees from 64 plots located in 50 year-old plus, natural, fully stocked, even-aged stands of paper birch (Betula papyrifera Marsh.) in Interior and Southcentral Alaska. Observed height-over-age data were modeled using the Chapman-Richards nonlinear growth model. Plots were grouped into five site quality classes based on tree height at breast-height age of 50 years. Polymorphic site index curves were developed from the data. The families of curves indicate different height growth patterns (polymorphism). Comparison of existing Alaskan anamorphic site index curves with the polymorphic site index curves developed in this study demonstrates differences in predicted heights at different levels of site quality. The polymorphic site index curves developed in this study should replace existing anamorphic curves since they represent a more accurate pattern of height growth for the range of paper birch in Alaska.