Effects of Herbivory by Moose on Flower and Fruit Production of Aralia Nudicaulis

Abstract

(1) The effects of herbivory by moose on the demography of the perennial herb Aralia nudicaulis were studied by determining the frequency and pattern of herbivory and by measuring the survivorship and reproduction of shoots of plants clipped experimentally. (2) The grazing was intense; 63% of flowering shoots and 33% of vegetative shoots were eaten. The proportion of shoots eaten increased with shoot density from 11% in quadrats with less than 9 shoots m-2 to 77% in quadrats with over 20 shoots m2. (3) In the experimental year, clipped shoots produced significantly fewer fruits and smaller leaves than intact shoots. (4) In the following year, leaf production was still significantly lower for clipped shoots than for intact shoots; in addition, clipping had lowered the chance of flowering significantly but had no effect on survivorship. (5) The results show that herbivory significantly alters the population structure of A. nudicualis by reducing the total number of flowering shoots and decreasing fruit production.