Sprouting and Carbohydrate Reserves of Two Wildland Shrubs Following Partial Defoliation

Abstract

Two wildland shrubs, little rabbitbrush and snowberry, were subjected to three intensities of defoliation at each of four distinct stages in the carbohydrate reserve cycle. These treatments, comparable to browsing and other forms of natural defoliation, were designed to determine the effects on sprouting and associated carbohydrate reserve levels the following spring. Little rabbitbrush plants had reduced carbohydrate reserves, shorter sprouts, and more sprouts following most defoliation tretments. In contrast, carbohydrate reserves increased in snowberry plants with all intensities of defoliation, but there were no significant variations in their sprouting characteristics. Most dormant buds on the root crowns of little rabbitbrush and snowberry plants that were protected from defoliation were prevented from developing as basal sprouts because of apical dominance. Removal of twig tips, however, stimulated more of these buds to produce sprouts. Once a sprout began to grow, a direct relationship seemed to exist between its elongation and the amount of carbohydrate reserves available to it.