In this paper we modify the classical Lotka–Volterra differential equations to analyze
competition between two aquatic plant species, a submersed plant and a
free-floating plant. We formulate and analyze a system of three differential
equations that control the dynamics of the free-floating plant biomass and both
aboveground and belowground biomass for the submersed plant. We investigate
our model to understand how plant competition is affected by grass carp
herbivory on the submersed plant’s aboveground biomass. We analyze both a
reduced model, for which the submersed plant is assumed to have constant
belowground biomass, and the full model. In each case, we compute stability
of equilibria and derive a minimal grass carp stocking rate such that the
free-floating plant may dominate the submersed plant. For the reduced model we
show that the rate at which grass carp are stocked may exhibit a hysteresis
effect.