Responses to Simulated Leaf and Root Herbivory by A Biennial, Tragopogon Dubius

Removal of 25 or 75% of leaf or root tissue, and 25% of both, was used to simulate above— and belowground herbivory on Tragopogon dubius. Plants with 25% of their leaf tissue removed did not differ significantly from controls in total biomass; those with any root tissue trimmed produced significantly less biomass while the 75% leaf removal treatment was intermediate. A similar pattern was exhibited for plant mortality and flower production. Plants that had one or more flowers removed by herbivores grew significantly larger and produced significantly more flowers than plants that lost no flowers, regardless of treatment. The greatest differences between treatments in nutrients allocation patterns occurred 1 d after manipulations were applied. Subsequently, differences between treatments moderated, and values tended to converge by 98 d postmanipulation, when the plants were harvested. Seeds had significantly higher nitrogen concentration levels than leaf or root tissue.