The article is devoted to reconstruction of paleoecological conditions at the border of Khazar kaganat and Slavic world at the end of the first millennium A.D. Subject to presentation being new materials of integrated natural science investigations regarding Mayatsky fortified settlement — one of the key sites of the Saltovo-Mayatsky archaeological culture in the East European forest-steppe. An integrated analysis of results of soil-and-stratigraphic, palynological, microbiomorphic and geochemical investigations regarding sediments of the ditch showed that during the beginnings of the fortified settlement in the first third of IX c. the environmental conditions were warmer and drier compared with modern ones. However, the end of existence of the fortified settlement, coinciding with the decline of Khazar kaganat in the middle of Х c., was connected with better conditions of humidification and, probably, with a colder spell.