Population viability analysis for herbaceous vegetation: A stochastic model and projections by simulation

Population viability analysis (PVA) is one of the major areas of research in ecological studies. Rapidity of changes occurring to biodiversity has increased the importance of PVA. Demographic and environmental stochastic events are continuously influencing population viability. Anthropogenic activities are altering these dimensions of operation, and are pressurizing the viability of population. Under these changing scenarios, it is imperative to find out how a population is driven towards extinction, and at what stage(s) human intervention is necessary to alter the course of direction. Keeping this in mind, the present study has been made to propose a suitable model and to study its behaviour through simulation experiments for PVA. The model is developed keeping herbaceous plants with three distinct phases in life cycle as a background. Different shocks occurring at the three phases separately and the fourth one occurring at any of the phases are considered in this study to take care of environmental stochasticity. Probabilities of occurrence of shocks and their levels of likely impact on population are considered. In all the simulations, population showed a 'perfect' oscillation. The long-term simulations revealed that the population oscillated between sizeable numbers. The model can be used to check the population viability exposed to environmental shocks with different probabilities. It can be used to find out critical levels of population for its continuity of existence. The model is good for populations with minimal dispersal abilities. The model can be used to predict the continuity of heterogeneous herbaceous populations where the species are functioning largely as facilitators.