COMPENSATORY SHOOT GROWTH IN TREMBLING ASPEN (POPULUS TREMULOIDES MICHX.) IN RESPONSE TO SIMULATED BROWSING

Abstract

Moose (Alces alces) browsing influences plant growth and architecture. We sought to determine the impact of the timing of moose browsing on bud development and growth in aspen shoots in the subsequent spring through simulation by clipping aspen (Populus tremuloides) stems in the field in June, July, and August 2005 at the University of Northern British Columbia, Prince George, BC. To observe new leaf+shoot development in aspen over a 60-day period, the top meristems of both simulated browse treatments and unbrowsed controls were harvested in January 2006, and incubated in a growth chamber that simulated local springtime conditions. Total leaf+shoot biomass produced from stems was higher for June- and August-’browsed’ stems relative to unbrowsed controls. Mean stem diameter was significantly higher and number of total buds significantly lower on clipped relative to unclipped stems. The number of buds that broke winter dormancy and became active in the growth chamber remained relatively constant for both clipped and unclipped aspen, but with fewer dormant buds on clipped stems than controls. Overall, our findings suggest that the mechanical effects of moose browsing on aspen stimulate the production of compensatory leaf+shoot biomass, and therefore potential browse.