A. IVANOVA, Y. TODOROVA, P. RANGELOVA and M. PANAYOTOV
University of Forestry, Dendrology Department, BG – 1756 Sofia, Bulgaria
Ivanova, A., Y. Todorova, P. Rangelova and M. Panayotov, 2013. Xylogenesis of Pinus heldreichii and Pinus peuce in Pirin Mts. Bulg. J. Agric. Sci., Supplement 2, 19: 229–232
Pinus heldreichii and Pinus peuce are tree species characterized by longevity. Previous studies have outlined the potential for constructing long tree ring chronologies, which may be used for studying the climatic variation in the past. A difficulty is the mixed climatic signal with negative effect of summer droughts, but also of extremely cold summers and the positive effect of warm winters. Therefore, for successful dendroclimatic analysis better understanding of the processes of tree ring production is necessary. Our aim within this project was to study the cambial activity and production of tracheids during the growth period. Old 100–250 years trees of P. heldreichii and P. peuce from natural forests in Pirin Mts. were chosen. Beginning from 2010 microcores was taken every 10 to 14 days. The samples were prepared with a sliding microtom GSL-1 and analyzed for the onset of cambial activity, the period of production of first cells and the period until cells were produced. In 2010 and 2011, the onset of cambial activity was delayed until the end of June – beginning of July. In 2012, it started at the beginning of June. The late start in 2010 and 2011 was probably due to cold periods in April and May. Despite this the trees produced tree rings with more rows of cells and higher width than all the rings in the period 2000–2009. This confirms our initial hypothesis that warmer winters promote the production of wider tree rings. The production of new cells continued until the end of September, while the differentiation – until the middle of October. In both years P. heldreichii trees produced more cells than P. peuce trees.