We have developed a system of plant functional groups (PFGs) for modelling dynamics and biodiversity estimation of forest ground vegetation. Species Ellenberg ecological values and phytocoenotic characteristics together with morphological traits were used to classify plant species into the functional groups . Ground vegetation patches dominated by species of different PFGs were distinguished in the forest floor. We have characterized biomass of these patches performing statistical analysis of biomass values taken from published data and results of field investigations combined into the database "Biomass" . The database contains data on aboveground and belowground biomass of species and groups of species occurred in the ground layer of boreal and hemiboreal forests of European Russia. There are more than 7000 records on biomass and productivity for 196 vascular species, 32 bryophytes and 4 lichen species and for tens groups of species. Biomass of vascular plants and bryophytes quite well differed between the patches dominated by species of different PFGs. According to statistical analysis results, the patches explain much more of biomass variance than the forest types; differences in the influence of the factors are more pronounced for belowground than for aboveground biomass. The values of the belowground biomass for all groups were higher than the values of the aboveground biomass, and differed between the analyzed groups to a greater extent than the values of the aboveground biomass. Database "Elements" on element concentrations of plants was also developed on the basis of results of field investigations in the North and the Middle Taiga. The database contains data on more than 2500 samples of 80 plant species. The PFGs also differed well in the content of the chemical elements in species that comprise the group. The groups differed most in the following elements: N, Mg, Ca, P, S, Mn, Al, Zn, Fe and slightly less C. We have proposed a conceptual model of dynamics of ground forest vegetation; a model compatible with the individual-based EFIMOD model of forest growth, carbon and nitrogen cycles in forest ecosystems . Spatial unit of the ground vegetation model is the same as spatial unit of the EFIMOD (0.5×0.5 м); it is a patch of the forest floor dominated by species from one or two functional groups. Development and analysis of the database “Elements” was supported by the Russian Science Foundation, project 16-17-10284. The results on modelling of ground vegetation were received under umbrella of POLYFORES project (ERA-NET Sumforest). REFERENCES: 1. Khanina, L.G., Bobrovsky, M.V., Smirnov, V.E., Grozovskaya, I.S., Romanov, M.S., Lukina, N.V., Isayeva, L.G., 2015. Ground vegetation modeling through functional species groups and patches in the forest floor. Mathematical Biology and Bioinformatics. 10, 15–33. 2. Khanina, L.G., Grozovskaya, I.S., Smirnov, V.E., Romanov, M.S., Bobrovsky, M.V., 2013. Analysis of database on the biomass of forest ground vegetation for modelling plant dynamics in forest ecosystem models. Khvoinye borealnoi zony (Coniferous in the Boreal Region). 31, 22–29. (in Russ.) 3. Komarov, A.S., Chertov, O.G., Zudin, S.L., Nadporozhskaya, M.A., Mikhailov, A.V., Bykhovets, S.S., Zudina, E.V., Zoubkova, E.V., 2003. EFIMOD 2 – a model of growth and cycling of elements in boreal forest ecosystems. Ecol. Model. 170, 373–392.