Pointer years of Norway spruce (Picea abies L. Karst.) tree rings on dry forest sites in Lithuania

Abstract

Research material (samples from tree stems) in all regions of Lithuania during 1995-2000 was collected. More than 50 research plots in mature Norway spruce forests were selected. Most of these plots (34) represent dry forest sites (Piceetum vaccinio-myrtillosum and Piceetum hepatico-oxalidosum). More than eight hundred tree-ring series from spruce trees were analysed. Latewood and earlywood widths were measured separately. During the research, two master chronologies (one for each site) were created. Using response function the correlation between tree-ring growth and meteorological factors (monthly precipitation and air temperature) was estimated. Pointer years of spruce radial increment during past sixty years were also estimated. The following significant pointer years with negative increment were identified: 1941, 1954, 1979, 1980, 1992 and 1993. Characteristic pointer years of positive increment were in 1946, 1961, 1962 and 1974. There are no clear differences in the geographical distribution of pointer years in 1946, 1954, 1962 and 1992. There are only differences in comparison between annual ring, latewood and earlywood increment in these years. Results of my research on Norway spruce have showed that even in a small territory like Lithuania (slightly bigger than 65 thousands km2), with hills no higher than 300 meters, there are significant differences in widths of tree rings.