Geochemistry of grass biocenoses: Biogenic cycles of chemical elements at contamination of the environment with heavy metals

The paper addresses the involvement of grass communities in biogenic cycles of chemical elements (Zn, Cu, Pb, Cd, Mn, Co, Cr, Ni, and Fe). Both the species composition and the suprasoil phytomass of phytocenoses in the Central Urals are modified in a gradient of contamination with heavy metals. The bioproductivity and subsequent mineralization of plant remnants are discussed with reference to two soil types that differ in agrochemical parameters. The contribution of agrobotanical groups to the biological exchange of chemical elements is proved to be controlled not only by the volume of annually dying suprasoil biomass but also by the intensity of processes mineralizing plant remnants in the contamination gradient. This modifies the cycles of chemical elements in natural contaminated biocenoses. The reaction of grass communities on environmental contamination can be viewed as partial counterbalancing of the adverse effect of chemical stress via maintaining a high enough level of the biological exchange of chemical elements.