The Sprouting of Sweetgum in Relation to Season of Cutting and Carbohydrate Content

Abstract

Because vegetative succession in the range of loblolly pine is toward a hardwood climax, successful pine regeneration sooner or later requires reduction of hardwood competition. It would be a great deal easier to cope with the competing hardwoods if they could not sprout. All hardwood species in this type are capable of sprouting, however, although there are differences among species. To devise effective and efficient methods for controlling hardwoods, the forester must know how and why environmental conditions and characteristics of the parent stem affect sprouting. In the southern Atlantic coastal plain, sweetgum (Liquidambar Styraciflua L.) is a major component of the hardwood understory. Its prevalence and its ability to sprout quickly, vigorously, and persistently make it one of the most serious competitors of pine seedlings. Reports concerning other species indicate that site quality, size of the parent tree and season of cutting are the most important factors influencing the sprout growth of a species. Good sites result in more vigorous sprouting than poor sites (25, 29). Sprouting generally seems to increase with the diameter (at breast height) of the parent tree up to five inches and decreases with diameters above six inches (20, 22). Sprouting is least from stumps cut during the period of active growth and greatest from those cut during the dormant season (6, 25). Because of year-to-year variation in seasons, Stoeckler (25) related sprouting to phenological development and found that cutting when the leaves were nearly full size produced the least vigorous sprouts. The seasonal trend of sprouting vigor is believed to be the result of the seasonal fluctuation of carbohydrate reserves (1, 25). Total carbohydrate reserves fluctuate in about the same pattern as sprouting vigor, declining sharply during spring growth to a minimum in early summer, building up to a peak in fall and going through a slight and gradual decline during the winter. This trend has been found in nearly every species studied, including fruit trees, forest trees, and woody shrubs (12, 14, 18, 24). Aldous (1) reported the absence of a seasonal trend in the carbohydrate content of buckbrush, but this finding is questionable in view of the consistency with which such a trend has been found in other species. Presumably a plant will die if food reserves drop below some critical level. In Connecticut annual mowing of brush-invaded pastures for four years at different times during the year resulted in nearly complete disappearance of woody growth from plots cut in June, July, or August while