The paper provides the research results representing the dynamics of species composition and production of wood stands in suramens of Mari El Republic Trans-Volga region as mathematical models. It was determined that there are 15 tree species growing on this territory, however the composition of a particular forest stand includes no more than seven tree species. Almost all suramen hydrotopes, with the exception of the swampy ones, are dominated by birch trees, the share of which is especially high in wet suramens, which proves the significant transformation of the forest structure. With the growth of tree stands the species composition inevitably changes towards original formations: in new and wet suramens the tree stand transforms into spruce forest mixed with linden and oak, while in wet suramens the forest stand transforms into spruce forest mixed with birch trees, and in swampy areas – into sticky alder forest. The greatest maximum plant biomass in new suramens is by pine trees, which are followed by spruce and oak trees. Aspen and birch trees are outsiders in this respect. In wet suramens the greatest plant biomass is produced by spruce trees while the least, by sticky alder trees. In terms of annual plant biomass increment the highest is by aspen trees in all types of suramens excluding the swampy ones. In complex plantations in terms of species composition with the growth of forest stand, there are distinct variations of the total tree bole biomass. This occurs due to gradual elimination of some species and their replacement with others. Forest stands in surames of Mari El Republic Trans-Volga region do not use their production capacity to the fullest. There are still reserves to be used. In new and wet suramens the birch and aspen may be replaced by conifers and in some cases even by oak. However, the final decision as on replacement should be taken based on economic calculations and ecological limitations. The paper also stresses that special attention of foresters should be paid on establishing the wood stands when the trees are still young.