Growth-Form Characteristics of Ancient Rocky Mountain Bristlecone Pines (Pinus aristata), Colorado

This report describes and illustrates growth-form characteristics of Rocky Mountain bristlecone pines (Pinus aristata) at several sites in the Rocky Mountains in Colorado. Most of this study concentrates on 1,000- to 2,500-year-old bristlecone pines; however, the report also describes some of the growth-form characteristics of younger trees (about 20 to less than 1,000 years old) in order to show the continuous changes in tree form from youth to old age. To better describe the trees in this study, some tree-structure nomenclature is introduced and a growth-form classification system is provided. Other topics include the relationship of the trees to their substrate and the potential changes in the growth forms of some bristlecone pines due to damage caused by fire, porcupines, impacts from tumbling boulders, and lightning strikes.