AIKIO, SAMI.
Department of Biology, University of Oulu, P.O. Box 333, FIN-90571 Oulu, FINLAND.
A simple resource consumption -based model of plant biomass is presented to predict the outcome of resource competition between mycorrhizal and non-mycorrhizal plants under varying degree of herbivore-induced mortality. A Michaelis-Menten with threshold -type growth function was used for the functional response of plant biomass to soil nutrient concentration. The minimum resource requirement level for zero net growth (D. Tilman's R*) was interpreted as the plant's resource competition ability. Mycorrhizal plants are predicted to tolerate more herbivory than non-mycorrhizal plants in low resource availability but an opposite prediction is given for high resource availability. Partial derivatives of R* with regard to different parameters of the model are suggested as measures of sensitivity of R* to changes in parameters. Their values differ between mycorrhizal and non-mycorrhizal plants as well as in low and high rates of mortality. The traits that correspond to highest sensitivities are suggested to be most important determinants of the resource competition ability of the plant.
Key words: benefit-cost-analysis, herbivory, model, resource competition.