FIRE INFLUENCE ON DYNAMICS OF STEPPE PHYTOCENOSES BELOW-GROUND PHYTOMASS IN BURTINSKAYA STEPPE (ORENBURG RESERVE)

Abstract

Steppe ecosystems are the most vulnerable to the influence of the pyrogenic factor. The study of the regularities of the vegetation cover restoration in the burnt steppe phytocenoses is urgent, as it is connected with the wide spread of fires in the steppe zone at present time. The increasing frequency and area of fires indicate a tendency of fires intensification, which ultimately can lead to significant environmental consequences. The authors studied the effect of pyrogenic factors on the dynamics of below-ground phytomass stocks of steppe phytocenoses on the territory of the sector “Burtinskaya Steppe” in Orenburg Reserve. The research area is located in the steppe zone of the Zavolzhsk-Ural region. The total area of the sector is 45 km². In August 2014, more than 20 km² of protected steppe burned on the site. After the fire two monitoring plots were laid, each plot included a control (B) and a burnt (A) plot. The research was conducted in 2015–2016. The geobotanical descriptions, registration of the above-ground and below-ground phytomass were conducted in spring, summer and autumn periods for each community. The obtained samples of below-ground phytomass were washed, dried at 105 °C and weighed. All above-ground phytomass was dried to air-dry state. The comparison of unburned and fire-damaged plots at all sites did not reveal statistically significant differences according to the nonparametric Mann-Whitney U-test (α <0.05) in the total stocks of below-ground phytomass and stocks of living below-ground phytomass. Differences in the stocks of dead below-ground phytomass were revealed by the second year of the study at one plot.