The Śnieżnik Massif, with its highest peak, 1,425 m a.s.l., is located in the eastern part of the Sudetes, a mountain range running along the border of southwestern Poland and the northeastern part of the Czech Republic. It forms one of the highest parts of the Sudetes, distinguished by its partial elevation above the upper forest line. The research area is a small mire, called "Torfowisko pod Małym Śnieżnikiem" (50º11'47"N, 16º49'17"E). The mire covers a flat summit surface, located at an altitude of ~1,245 m a.s.l, approximately 600 m ENE from the culmination of Mt Mały Śnieżnik (1,326 m). At the top, but also in the middle of the slope, there are numerous flattened areas that favoured the formation of peat bogs. The maximum observed thickness of peat covers at the pass below the Mały Śnieżnik peak is lower than 75 cm, and most frequently reaches about 50-60 cm. The highest parts of the Śnieżnik Massif are covered with a Norway spruce (Picea abies) forest of the upper mountain forest zone. The trees are distinctive due to the frequent occurrence of broken tops caused by strong wind and weight of the ice and snow caps in winter. Fieldwork was performed in two campaigns in 2023: in early June and late July. Tree ring width (TRW) was measured under a stereoscopic microscope to 0.01 mm using LBD_Measure software (version 1.0). Tree ring width measurements from sample TM15 yielded 370 tree rings in the radius r1 and 370 tree rings in the radius r2 (counting from the same tree ring adjacent to the pith, to the bark). Thus, the sequence can be dated to the period 1653–2022. The spruce from which the sample originated is growing at an altitude of 1251 m above sea level in the central part of the mire “Torfowisko pod Małym Śnieżnikiem” (50.1960601N, 16.8212750E). It is 14.5 m high, and its DBH equals 31 cm. The average tree ring width of the TM15 spruce equaled 0.34 mm/year for the radius r1, and 0.31 mm/year for the radius r2 (on average 0.33 mm/year for TM15). Numerous tree rings are very narrow, i.e., 0.06 mm (3–4 rows of cells), and the widest tree rings reach 1.38 mm/year for r1 and 0.93 mm/year for r2. The period 1653-1771 displays rather variable tree ring widths. On several occasions tree ring widths exceed 0.8 mm/year (on average 0.44 mm/year). From 1742 to 1943, the selected tree TM15 has very narrow tree rings – on average 0.19 mm/year and there is little variability in tree ring width (below 0.5 mm). In the period 1944–2023, the tree ring width increases again to an average of 0.54 mm/year, and displays strong variability. An increasing trend in tree ring width is observed in the period 1944–1975, and a decreasing trend in tree ring width is observed in the period 1976–2023.
Tree-ring width of oldest Norway spruce (Picea abies L.) in “Torfowisko pod Małym Śnieżnikiem”; 1st column - year, 2nd column - tree-ring width in mm.