Temporal dynamics of cambial activity and wood and phloem formation was monitored in European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) at the sites Panška reka near Ljubljana (400 m a.s.l.) and on Menina planina (1200 m a.s.l.) from 2006 until 2014. The monitoring is based on histometrical analysis of stem tissues of adult trees including cambial zone, xylem (wood) and phloem. Samples
(micro cores) for analyses were taken from trees using a Trephor tool at weekly intervals during the growing seasons. Micro cores were embedded in paraffin in order to cut cross-sections and make permanent slides for observations under the light microscope. We
always measured the width or counted the number of cells in the cambium, forming xylem and forming phloem increments. The measurements or counting were performed along three radial files of xylem and phloem growth rings and the cambial zone. We recorded
the phases of xylem formation: PC – post-cambial extension growth, SW – deposition of secondary wall and lignification, MT – mature cells. In phloem we separately recorded the formation of early and late phloem. Research on beech was conducted in 2006
and from 2008 until 2014, and on spruce from 2009 until 2014. The monitoring and sampling continues. We present some main findings on the beginning, dynamics and cessation of processes which lead to formation of wood and phloem annual growth layers in beech and spruce from both sites. We show how the processes depend on climatic factors. We also present how the spruce data included in a global data set of conifers helps to predict how tree productivity (and survival) will change due to climatic change.
The described processes and their variability are still poorly understood; it is therefore necessary to continue the research presented. The results provide basic knowledge to better understand productivity of trees and forest stands, wood quality, the impact of climate change on tree growth and survival, accumulation of carbon and other processes.