Growth in Male and Female Aspen Clones: A Twenty-Five-Year Longitudinal Study

Abstract

Field studies of Populus tremuloides at two sites in northern lower Michigan were conducted to compare the vegetative growth of ramets for male and female clones over a 25—yr period. Thirty—one clones were surveyed in 1981; 23 of these clones had been surveyed in 1956. There was no significant difference between the sexes in density (basal area divided by clonal area), mean diameter at breast height, oldest ramet, or mean annual ring—width growth. Relative to male clones, female clones had larger numbers of ramets and greater basal area, showed a larger increase in areal spread over the 25—yr period, and had a different size class distribution. These data do not support the hypothesis that greater female investment in sexual reproduction associated with fruit production is at the expense of vegetative growth. The results suggest that further empirical longitudinal studies and measures of clonal growth as well as ramet growth are necessary to clarify the relationship of sexual reproduction and vegetative growth in long—lived clonal plants such as trembling aspen.