Abiotic factors affect the Phragmites australis productivity in lakes in the south of Western Siberia

The article presents the results of studying phytomass, stem height and density of thickets (herbage) of Phragmites australis, one of the most common aerial-aquatic plant in the south of Western Siberia. This region is distinguished by a rare combination of chloride, sulfate and soda lakes in a relatively small space. As an eurybiont, reed is highly resistant to water and soil salinity, but high salinity adversely affects its growth and development. The aim of the work was to assess the degree of abiotic factors (pH, mineralization) effect on the quantitative characteristics of reed growing in water bodies with different water mineralization: from 0.005 to 387.6 g/L. In total, we studied 59 freshwater, brackish-water (oligo-, meso- and polyhaline) and hypersaline water bodies, located in various natural zones (southern taiga, forest, forest-steppe, steppe and dry-steppe) in the south of Western Siberia. The studies were carried out in late July – early August from 2012 to 2020 during the period of maximum vegetation of plants. As a result of the studies, it is shown that the optimal for reed growth and development is water mineralization from 0.5 to 5.0 g/L, when the highest values of biomass and plant height are observed. A model based on redundancy analysis (RDA) was built and a correlation analysis was carried out to assess the dependence of phytomass, shoot height and herbage density on abiotic factors. We took into account pH, salinity, and Ca2+, Na+, Mg2+, K+, HCO3-, Cl- and SO42- content. We found that pH and determined by Ca2+ water hardness are the limiting factors in freshwater lakes. In brackish-water meso- and polyhaline, as well as in saline hyperhaline water bodies reed phytomass is affected by a whole range of factors, while shoot height is affected by pH, chlorides, and water hardness, and grass stand density is affected by chlorides and sulfates.