Vibrational resonance in groundwater-dependent plant ecosystems

We report the phenomenon of vibrational resonance in a single species and a two species models of groundwater-dependent plant ecosystems with a biharmonic oscillation (with two widely different frequencies \omega and \Omega, \Omega >> \omega) of the water table depth. In these two systems, the response amplitude of the species biomass shows multiple resonances with different mechanisms. The resonance occurs at both low- and high-frequencies of the biharmonic force. In the single species bistable system, the resonance occurs at discrete values of the amplitude g of the high-frequency component of the water table. Furthermore, the best synchronization of biomass and its carrying capacity with the biharmonic force occurs at the resonance. In the two species excitable and time-delay model, the response amplitude (Q) profile shows several plateau regions of resonance, where the period of evolution of the species biomass remains the same and the value of Q is inversely proportional to it. The response amplitude is highly sensitive to the time-delay parameter \tau and shows two distinct sequences of resonance intervals with a decreasing amplitude with \tau.