Cedro, A. and Lamentowicz, M. 2008. The Last Hundred Years’ Dendroecology of Scots Pine (Pinus sylvestris) on a Baltic Bog in Northern Poland: Human Impact and Hydrological Changes. Baltic Forestry, 14 (1): 26-33

The study was aimed at determining age of the trees growing on the cupola of the Stążki raised bog, at elucidating anthropogenic influences on the water level in the bog, and at exploring effects of climatic factors on the Scots pine tree-ring growth. Samples were collected, with Pressler’s bores, from 22 Scots pines and from a single downy birch. Tree-ring widths, measured to 0.01 mm, were used to compile – based on the classic dating methods – 143-year-long (1862-2004) ST chronologies. The mean annual ring growth was found to amount to 0.87 mm. The chronologies obtained served as a basis with which to analyse signature years and response functions. Dendroclimatological analyses produced no unequivocal and statistically significant results: the signature years and response function analyses failed to identify a dominant factor and to indicate unambiguously a period during which the weather components studied exerted a decisive effect. Because of that, no climatic reconstructions were carried out. The ring growth of the trees examined was found to be primarily affected by changes in the water level, related mainly to anthropogenic activities. The bog evolution (drying-out and Scots pine invasion) was reconstructed with this assumption in mind. A mass appearance of trees on the bog was dated at the last decade of the 19th century. It was assumed to be triggered by draining operations carried out to lower the water level so that peat could be cut. As a result, conditions amenable for the bog surface to be colonised by Scots pine seedlings were created. The data obtained are important from the standpoint of raised bog conservation; they demonstrate that pine forests growing on raised bogs are not always the final stage of succession, but provide evidence of disturbed bog hydrology and serve as an indicator of a perturbed bog ecosystem.

Key words: peatland, Baltic bog, dendrochronology, tree-ring width, Pinus sylvestris L., environmental reconstructions.