LAUSR

Betula pendula L. is one of the forest trees having local distribution areas in Turkey. When it had a wide distribution area during Late Glacial time of Turkey, its distribution decreased at the end of Late Quaternary. The purpose of the paper is to discuss its past and present distribution in Turkey, climate features in growing areas by focusing on the lowest distribution area in Turkey. This species has local distribution areas in mainly East Anatolian Region of Turkey together with Kayseri-Erciyas Mountain. When its known distribution area ranges 1300-2850 m in Turkey, we focused on the lowest distribution areas in Munzur Valley 1333-1206 m a.s.l. The species grows with riparian trees (such as Salix caprea, S.alba, Alnus glutinosa etc.) on valley bottom having high level of ground water like wetland forest. In Marho Bridge and Joining Point of Mercan River, distribution of Tamarix gracilis ends and birch trees start to grow. In this altitude it is represented with small stands and individuals on the river banks. The area has bottom land with high level of ground water table and deep alluvial soil, and semi-dry climate. The reason of its presence here may be these optimum soil and water conditions. After flat bottom land, the distribution of the species stops suddenly. For that reason this unique and special ecosystem should be protected as a whole.