Results of studies of post pyrogenic vegetational associations' renewal of feather fescue grass steppe «Askania Nova»

Abstract

The results of studies of post pyrogenic vegetational associations' renewal of the feather fescue grass steppe that is under protection of the Biosphere Reserve «Askania-Nova» are given in the paper. The fire's effect is one of most ancient and powerful factors that forms and determines the development of a steppe ecosystem. The steppe fires are rather often phenomenon at the natural core area of the Biosphere Reserve «Askania-Nova» due to the following factors: 1) availability of long dry period in summer; 2) a plane where any natural obstacles for spreading of the fire are absent; 3) steppe vegetation, which complete the stage of active vegetation by the middle of summer and can accumulate the considerable amount of a dead organic matter (mort mass). About 300 geobotanical descriptions were performed for studies according to the Braun-Blanquet technique (Braun-Blanquet, 1964). Also elevated phytomass was selected in accordance with generally accepted techniques (Bazilevich, 1967; Yaroshenko, 1969; Ramenskiy, 1971; Rodin, Gortinskiy, 1971). The phytomass was divided into biomass (living organic matter of vegetational origin) and mortmass (dead organic matter of vegetational origin) under the field conditions. Cereals (by species), sedges, annual and perennial herbs, and cryptogamous plants were marked out separately in the biomass composition. The mortmass fraction was divided into dead standing grass (vegetational remains which conserve a connection with maternal plant) and litter (dead organic mass of plants which lost the connection with maternal plant). The above-ground phytomass was selected on the site «Stara», where the large-scale fire had happened in 04–05.08.2012, under the ecological line «flaWslope^depression». The postpyrogenic renewal of vegetational association Stipa ucrainica (+ S. capillata, S. lessingiana) + Festuca valesiaca was studied also at 68 sq. of the site «Pivdenny» («South»), which had undergone the double fire effect in February and July 2007. The vegetative vascular plants species which have resumed their development were recorded at the permanent route and phenological stations at the site «Stara» in a month after the fire. As a result about 33 species of higher vascular plants belong to 31 genuses of 17 families. The families Asteraceae (Artemisia austriaca Jacq., Carduus uncinatus M. Bieb., Crepis ramosissima D'Urv., Lactuca serriola L., Tragopogon major Jacq.) and Poaceae (Bromopsis inermis (Leyss.) Holub, Festuca valesiaca Gaudin, Leymus ramosus (Trin.) Tzvelev, Stipa ucrainica P. Smirn., Poa angustifolia L.) are predominant by the number of species. When studying process of the post pyrogenic vegetational associations' renewal at the site «Stara» it has been determined that the changes occurring in vegetational associations owing to the fire effect (decreasing of abundant blooming of dominant plants' species, reducing of lichen cover, release the area from the dead organic matter of vegetational origin, and therefore increasing of the area of open ground) facilitate to a significant increase of abundant blooming and shares of annual and biennial herbs in grass stand, growth of the number of light-loving species of ground algae, and also spreading of rhizomatous species Leymus ramosus on the watersheds. Precipitations of vegetative season (march-june) influence on the renewal on elevated phytomass of dominant grass stand species before the fires.