The hilly Danubian plain - the most northern geomorphologic area of Bulgaria.
Situated between the Danube river and the fore-Balkan, it reaches the lower reaches of the river Timok (which forms the border with Serbia) to the west, and the Black Sea to the East. Whit in these outlines, its average width is 28 km in the Western part, reaching 60 km between Nikopol and Lovetch, and 120 km at Silistra. The Danube plain has a plato like and hilly relief, which is segmented by broad valleys of the rivers flowing into Black Sea.
The greater part of the plain as 100-250 m above sea level. Many plato like systems are formed in different parts of the plain cut by rivers, those of Lom, Karaboaz, Svishtov, Nikopol, Shoumen, Madara, Royak, Provadia, Frangen and others. The geomorphologic origin of part of these plateaux is sarmatian limestone, which has played an important role for teh resulting vegetation.
Danube plane - climate and physiogeography
The climatic conditions in the area are from temperate to truly continental, with the sea climatic influence felt only in the extreme eastern strip of 25-30 km. The average amount of rainfall per year is 550-600mm whit a rainfall in maximum in summer 30-32% and minimum in winter 20-24%
The physicogeographical conditions in the plain have determined the development of black earth soils (on loess and loess-like formations), and of the leached black earth soils (chernozem) in association with gray formed soils. The primary forest -steppe and forest cover of mixed oak forest has already been largely destroyed by human economic activity. Today it is to be found only in the protected areas and the forest massifs which have survived.
The forest cover and lakes along the Danube river
The lakes along the Danube and the islands in the main river are most vital to the conservation of biological diversity. These are the lakes of Srebarna, Malak, Preslavetz, Garvansko Blato (marsh), the former marshes turned into fisheries near the villages of Nova Tcherna and Metchka, the island Tzibar, Vardim, the Belin group, Kalimok, and others.
The forest cover is comparatively well preserved only in the Ludogorie. It consists mainly of thermophilic forests of Turkey oak and Hungarian oak, and more seldom of hornbeam, silver lime and others. With few exceptions, the forest are of offshoot origin.
Evidences of great wood have survived in several places in the Danube plain, as well as in Thrace. Most of them are protected: Tulovska, Vetrenska and Aytoska Koria, Genchov orman and others.
Legend has it that the Bulgarian Tsar Simeon the Great camped under the "Tzar oak" in the Tulovska Koria during a march against Constantinople. This pedunculate oak is more that 1200years of age.
