Site Index of Balsam Poplar/Western Black Cottonwood in Interior and Southcentral Alaska

Abstract

Stem analysis data were obtained from 268 balsam poplar (populus balsamifera L.) and black cottonwood (P. trichocarpa Torr. & Gray) trees on 67 sites in interior and southcentral Alaska during 1988-1990 for the purpose of height and volume growth analysis. A modifiedform of the Chapman-Richards growth model was used to produce polymorphic site index curves. Wide variations in curve shape, which were evident in region-to-region comparisons, required stratification ofthe data. Site index curves for balsam poplar north ofthe Alaska Range were produced using one equation and data from 35 sites. The remaining 32 sites, located south ofthe Range, were divided by landform (fluvial vs. upland). Sites on the middle and upper Susitna and Chulitna Rivers were placed in a separate fluvial class, giving three equations for sites south of the Range. The four equations produce the first polymorphic site index curves for poplars in Alaska. North. 1. Appl. For. 15(4):174-181.