| Summary: | This study focuses on the active responses of plants to herbivore damage, specifically
on the ability of plants to regrow following an episode of herbivory. The Continuum of
Responses model (CRM) and the Growth Rate model (GRM) make some conflicting
predictions about the effects of soil nutrient availability on compensatory growth by grazed
(clipped) plants. A factorial field experiment was conducted to examine the effects of longterm
fertilization, short-term fertilization and clipping on the rate of (re)growth and the
amount of (re)growth of three herbaceous perennial species, Achillea millefolium, Festuca
altaica and Mertensia paniculata. Plants were collected from areas with different soil
nutrient levels (low soil fertility and high soil fertility), planted in a common garden in the field
and subjected to one of three simulated herbivory events (0%, 50% and 100% leaf loss) and
one of two fertilizing treatments (no fertilizer and fertilizer addition).
Concordant with both models, clipping was detrimental to plant growth which
decreased as clipping intensity increased. From the plant's perspective, the impact of
herbivory on the proportional leaf area of clipped plants relative to undipped controls, was
independent of short-term fertilization. When biomass was measured, short-term fertilization
reduced the compensatory ability of A. millefolium and M. paniculata, but improved it for
F. altaica. From the animal's perspective, the impact of herbivory on the absolute size of
clipped plants relative to controls was reduced by short-term fertilization, regardless of
species and the measure of growth considered. Under natural soil nutrient conditions, M
paniculata is more likely to compensate for leaf loss than A millefolium and F. altaica.
These results indicate that short-term nutrient availability may affect the compensatory growth
of clipped plants, but compensatory responses of the three species studied were only partly
consistent with the predictions of the two models. === Science, Faculty of === Botany, Department of === Graduate
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