Elevational gradient of neoformed shoot growth in Populus tremuloides

Abstract

Determinate growth involves cessation of leaf formation prior to the end of the growing season, whereas indeterminate growth involves leaf formation for as long as environmental conditions allow. Quaking aspen ( Populus tremuloides Michx.) has been described as having both types of growth. This variation is partially due to canopy bud position, but environmental factors may also contribute. In this study, buds from the same canopy position of aspen trees in northern Colorado, USA, exhibited less neoformation with increasing elevation (R2 = 0.78). Evidence suggests that this is primarily a response to the characteristically cooler temperatures and shorter growing seasons of higher elevations.