An interbiome comparison of the principal ecosystem functions of a natural flood-plain forest and its secondary communities (Seminatural alluvial meadows and man-made agrocoenoses) was performed, using alluvial biotopes in southern Moravia. The primary production of meadows in some cases surpassed the production of a flood-plain forest and that of a sugar-beet stand. In the forest, the efficiency of the utilization of solar energy was c.1.1%, in grassland, according to type it was 1.0-1.8% and in field crops 1.4-1.8%. The nutrient uptake amounted to c.650 kg of pure nutrients ha-1 yr-1. While the alluvial meadows and forests made use of nutrients transported in flood waters, without any supplementary energy, up to 778 kg of pure nutrients ha-1 (in the form of mineral fertilizers) had to be supplied to the arable land.