The paper addresses the removal of chemical elements by suprasoil and subsoil phytomasses of herbaceous phytocenoses and their subsequent return to soil during decomposition of plant remnants. The obtained results allowed us to evaluate the biogeochemical cycles of essential (Zn, Cu) and toxic (Pb, Cd) elements in natural biogeocenoses of the Middle Urals. It has been shown that the intensity of such an exchange in areas subjected to variable anthropogenic impact is determined not only by the direct influence of mobile forms of chemical elements, which are contained in soils and operate as environmental pollutants, but also by a combination of edaphic (physicochemical parameters of soils), coenotic (abundance and correlation of agrobotanical groups in phytocenosis) and microbiological (level of evolution of soil microbiocenosis) conditions.

This paper is concerned with the phytomass of herbaceous phytocenoses growing in anthropogenically impacted areas in the Middle Urals at different stages of succession along the heavy-metal pollution gradient. Cenoses of young soils of dumps have less resistance and higher sensitivity to changes in weather factors, in contrast to the phytocenoses of the deposits. It is shown by general regression models that the epiterranean and subterranean biomass of cenoses on technozems depends on Selyaninov’s hydrothermic coefficient for September and the amount of precipitation in October–November of the previous year and in January–May of the current year. The degree of this dependence for cenoses under research is determined by edaphic conditions that affect the species diversity and dominance structure.

The structural and functional diversity of the main ecological trophic groups of soil microorganisms in meadow soils of the Central Urals anthropogenically contaminated with heavy metals was studied. The increase in the total numbers of these microorganisms in technozems, in comparison with those in agrozems, is due to the higher abundance of iron-reducing, denitrifying, nitrogen-fixing, and sulfate-reducing bacteria, an increase in cellulolytic activity, and the dependence of these characteristics on the toxic load of the soil. A reductive structure of the microbial community with the predominance of r-strategists, which reflects earlier stages of microbiocenoses succession under soil contamination, is formed under soil pollution with heavy metals.

Consideration is given to production and decomposition processes in herbaceous communities exposed to chemical pollution with heavy metals in the Middle Urals. High variation in the aboveground phytomass of agrobotanical groups (legumes, forbs, grasses) is due to spatial heterogeneity of soil pollution levels and consequent changes in the species composition of plant communities in the areas studied. Therefore, nonparametric statistical methods have been used (Kruskal–Wallis test with subsequent pairwise comparisons by Wilcoxon–Mann–Whitney with Bonferroni correction for multiple comparisons). The phytomass of legumes remains unchanged in the increasing pollution gradient, while the contribution of forbs to the total phytomass decreases and that of grasses increases. Soils rich in nutrient elements can maintain a high rate of plant debris decomposition, counterbalancing the adverse effect of increased heavy metal concentrations on relevant processes. The balance between production and mineralization processes provides for the sustainable, long-term existence of herbaceous communities under conditions of intense pollution of the natural environment.

Anthropogenic transformation of soils and specific features of herbaceous plant communities have been studied in areas polluted with heavy metals. With regard to landscape and edaphic conditions, all test areas have been divided into two groups: agrozems and technozems. Phytocenoses in test areas of the background and buffer zones belong to the glycophytic variant of meadow vegetation type and to the premeadow stage of progressive succession, respectively. Chemical pollution leads to a decrease in coefficients of similarity between communities and an increase in taxonomic diversity due to reduction in species saturation of genera and families, with a rise in the proportion of monotypic taxa. The influence of chemical pollution on the species saturation of plant communities is stronger than that of community type and coverage of species.

Изучена антропогенная трансформация почв и особенности травянистых растительных сообществ в условиях химического загрязнения тяжелыми металлами. По ландшафтным и почвенным условиям изученные участки разделены на две группы – агроземы и техноземы. Фитоценозы участков фоновой и буферной зон относятся к гликофитному варианту лугового типа растительности, импактной – к предшествующей лугам стадии восстановительной сукцессии. Химическое загрязнение приводит к снижению коэффициентов сходства между сообществами и повышению таксономического разнообразия за счет снижения видовой насыщенности родов и семейств и повышения доли монотипных таксонов. Химическое загрязнение в большей степени, чем тип сообщества и группа почв, влияет на видовую насыщенность и проективное покрытие видов.

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.

Рассмотрено участие сообщества травянистых растений в формировании биогенных циклов химических элементов (Zn, Cu, Pb, Cd, Mn, Co, Cr, Ni, Fe). Показано изменение видового состава и наземной фитомассы для фитоценозов Среднего Урала в градиенте загрязнения тяжелыми металлами. Рассмотрены также процессы биопродуктивности и последующей минерализации растительных остатков для двух типов почв, различных по агрохимическим параметрам. Установлено, что вклад агроботанических групп в биогенный обмен химических элементов определяется различием не только в ежегодно отмирающих объемах надземной фитомассы, но и в градиенте загрязнения, а также в интенсивности минерализации растительных остатков. В результате при химическом загрязнении среды изменяется круговорот химических элементов в природных биогеоценозах. Реакцию травянистых сообществ на загрязнение среды можно рассматривать в качестве частичной компенсации негативного влияния химического стресса, поскольку поддерживается достаточный уровень биогенного обмена химических элементов.