By learning why aspen stands gain more health when subjected to duress, forest managers are helping to stimulate aspen regeneration. Aspen trees produce two different hormones under opposing circumstances. One, called auxin, is a growth inhibitor. Auxin is common to mature aspen trees and ensures that other species don t compete with a tree or stand for nutrients. Because aspen primarily reproduce through suckers a biological process whereby new trees grow from an existing tree s roots a tree can inhibit the growth of the new tree, called a clone, with auxin flows.
Studies show that disturbance can reduce the flow of auxin.
Interference with the auxin supply by cutting, burning, girdling or defoliation decreases auxin concentrations in roots. Schier works for the Forest Service s Intermountain Forest and Range Experiment Station in Ogden, Utah. Schier also points out that aspen trees produce a growth-initiating hormone called cytokinin, which is also produced when trees are disturbed. On the Sawtooth National Forest, biologists Garwood and Bumpus have previously worked on ways to promote aspen regeneration. The idea, Garwood said, was to decrease auxin flows and increase cytokinins to stimulate sucker production.