Theory of the ideal forest. Complex system can be understood using an idealized system with simple and predctable behaviour. This approach is common in physics, but currently it has begun to be applied in biology as well. Here I show that terrestrial vegetation can be interpreted as various deviations from an ideal forest. The ideal forest is characterized by several simple regularities, namely the power-law frequency distribution of age (and size) classes (tree abundance is inversely proportional to trunk cross-section), and consequent equivalency of energy utilization among age classes.