The Long-Term Dynamics of Stocks of the Live Aboveground Phytomass in a Steppe Phytocoenosis after a Fire (Based on the Example of the Burtinskaya Steppe Site of the Orenburgsky Reserve)

In recent years, in the arid regions of Russia, there has been a catastrophic increase in the area and frequency of fires in the steppes. At the same time, the entire above-ground part of phytocenoses burns out, which significantly reduces the reserves of the live above-ground phytomass, the productivity of communities, and changes the structure and composition of steppe phytocenoses. The purpose of our work was to study the effect of the pyrogenic factor on the stocks of the live aboveground phytomass and determine the timing of its recovery. In the Burtinskaya Steppe area of the Orenburgsky State Nature Reserve six monitoring sites were laid in 2015 after a fire, each included a control (unburnt) site and a burnt site. To identify the features of the dynamics of the stocks of live aboveground phytomass, standard geobotanical methods and the method of cutting areas were used. The studies were carried out in the 2015–2020 period. As a result of studying the effect of the pyrogenic factor on the vegetation cover of the steppes, it was found that the reserves of live aboveground phytomass (g/m²) reach the value of the control communities in the second year of the study. The seasonal dynamics of live phytomass stocks from 3–4 years after the fire depends more on the composition and type of the community and not on whether it was exposed to a pyrogenic factor. Over the entire period of the study the share of live phytomass reserves in the total aboveground phytomass of burned communities approached the values of control phytocenoses; however, there was always more in the control, which indicates incomplete restoration of the structure of the aboveground phytomass in the burnt areas.