Effects of surface flooding on biological properties of meadow-chernozems in Kamennaya steppe

Under study were the soils developed in flat watersheds with suffusion depressions and subjected to excessive seasonal flooding in Kamennaya Steppe, Talov district and Voronezh region of Russia. Among them are migrational-mycellary chernozem (Haplic Chernozem (Clavic, Pachic) on convex microrelief elements, the clay-illuvial eluvial weakly gleyic chernozem (Luvic Stagnic Phaeozem (Clayic, Pachic) in shallow depressions with seasonal flooding for two weeks in a year and the clay-illuvial quasigley eluvial vertic chernozem (Luvic Vertic Stagnic Phaeozem (Epiloamic, Endoclayic, Pachic) in deep depressions with seasonal flooding in the period from one to three months. A complex of ecological-trophical groups of microorganisms (amilolytics, actinomyces, micromyces, denitrifiers and aerobic azotobacters) along the soil profile has been studied; soil sampling was taken at the end of the summer (in August). It is shown that the excessive surface flooding has a great influence on the following groups of microorganisms: microscopic fungi (dried aerobic microorganisms), actinomyces (continental branch of prokariot with wide ecological amplitude) and denitrifiers (typical anaerobic forms). The population of micromyces is decreasing from 5.6 to 3.5 lg KOE/g with increasing the anaerobic conditions, whereas actinomyces are increased reaching 4.2 lg KOE/g in moist horizons of hydromorphic chernozems; denitrifiers are rather active (2.5-3.6 lg КОЕ/g soil) only in soil of depressions with traces of seasonal flooding. The duration of seasonal flooding is a factor changing the structure of the microbial community in which the dominants are alternated in groups of microorganisms. The ratio between these groups of microorganisms can be used for assessing the aerobic/anaerobic conditions for their habitat in soils of the steppe zone.