The cambium activity of Quercus petraea (Mattuschka) Liebl (sessile oak) in Atatürk Arboretum (Belgrade Forest, Istanbul) was studied by mounting 5 manual and 5 electronic dendrometers on 5 dominant trees very near to each other (2-5 m). Cambium activity began during the first week of May in 2003, and 1 month earlier, the first week of April, in 2004. | Turk J Agric For 30 (2006) 429-438 © TÜB‹TAK Cambial Activity of the Sessile Oak (Quercus petraea) in Belgrade Forest, ‹stanbul Ünal AKKEM‹K1,*, Hatice ÇINAR YILMAZ2, Orhan SEVG‹3 1 ‹stanbul University, Faculty of Forestry, Department of Forest Botany 34473 Bahçeköy, ‹stanbul - TURKEY 2 Atatürk Arboretum, 34473 Bahçeköy, ‹stanbul - TURKEY 3 ‹stanbul University, Faculty of Forestry, Department of Soil Science and Ecology 34473 Bahçeköy, ‹stanbul - TURKEY Received: Abstract: The cambium activity of Quercus petraea (Mattuschka) Liebl. (sessile oak) in Atatürk Arboretum (Belgrade Forest, ‹stanbul) was studied by mounting 5 manual and 5 electronic dendrometers on 5 dominant trees very near to each other (2-5 m). Cambium activity began during the first week of May in 2003, and 1 month earlier, the first week of April, in 2004. The fast growing season for both years was May to July, accounting for 90% of diameter increase. Earlywood/latewood ratios measured on tree rings varied principally with changes in latewood widths, as affected by climate. The highest and most significant correlations were between soil moisture at different depths and 10-day lagged growth forward, in 2003, and in 2004. We found only slight summer dormancy in this humid region, restricted to dry and hot summer days. Key Words: Quercus petraea, sessile oak, cambium activity, dendrometer, Belgrade Forest, Atatürk Arboretum ‹stanbul-Belgrad Orman›’ndaki Saps›z Mefle (Quercus petraea) Kambiyum Faaliyeti Özet: ‹stanbul - Belgrad Orman›, Atatürk Arboretumunda bulunan Quercus petraea (Mattuschka) Liebl. (Saps›z mefle) a¤açlar›ndan dominant olan ve birbirlerine çok yak›n bulunan (2-5 m) 5 tanesine, manual ve elektronik dendrometreler ba¤lanarak, kambiyum faaliyeti incelenmifltir. Kambiyum faaliyeti, 2003 y›l›nda may›s ay›n›n ilk haftas›, 2004 y›l›nda ise nisan ay›n›n ilk haftas›nda bafllam›flt›r. Kambiyum faaliyetinin bafllama dönemleri aras›nda, s›cakl›¤a ba¤l› olarak 1 ay .