The vegetation cover in the study area has been examined by a number of authors: A.F. Middendorff (1882), V.I. Kushlevsky (1990), V.I. Masalsky (1985, 1910), O.E. Knorring (1912), S.S. Nestruyev (1912), P.A. Baranov (1925), M.V. Kultiasov (1927), M.G. Popov (1928, 1929), D.N. Kashkarov (1927), N.N. Dzens-Litovskaya (1928), and E.P. Korovin (1934).