Phenology of wood formation in different coniferous species from Obcina Feredeului, Romania

The dynamics of the cambial activity and the formation of the xylem of Norway Spruce (Picea abies), Silver fir (Abies alba), European larch (Larix decidua) and Scots pine (Pinus sylvestris) from Obcina Feredeului region (experimental plot Deia), were studied during the 2013 growing season. The tree ring formation phases have been analyzed using wood microcores, collected weekly. The number of cells found in the cambial phase, cells enlargement, cell wall thickening and mature cells have been analyzed and discussed in terms of onset, cessation and duration of development. The onset of the cambial activity in spruce occurred around April 5th, while the most growth through a number of cambial cells occurred around June 28th. The onset of the cambial cell division in fir and larch occurred during the third week of March. In the case of Scots pine, the cambial activity began around March 15th, while at the end of April the cambial cells have reached their maximum number of cells. The research findings have confirmed the varied dynamics of the tree ring formation stages among species.