Concepts and simple empirical models that are useful in the study of the quantitative aspects of evolutionary ecology of plant - plant interactions is discussed and developed, and the use of simple empirical models in the statistical analysis of plant ecological data is exemplified. Special attention is paid to the consequences of the sedentary life form of adult plants and the subsequent strong interactions between neighbouring plants. The monograph provides an overview of different evolutionary and ecological empirical plant population models and conceptual links between different modelling approaches, e.g., spatial individual-based or plant size explicit modelling and the equilibrium conditions of mean-field models. The biological information underlying the discussed models is only briefly discussed. Christian Damgaard is Senior Scientist at the Department of Terrestrial Ecology, the National Environmental Research Institute.