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The aim of the study was to determine the impact of land relief on site index and growth parameters (height, diameter, slenderness) of Scots pine (Pinus sylvestris) stands on inland dunes in the Toruń Basin (N Poland). The study was conducted on 150 plots situated on north− and south−facing dune slopes (54 pairs of twin plots) as well as in intra−dune depressions (42 plots). Height and diameter of ten the thickest pines per 0.1 hectare was measured, and next site index as a potential height of a stand at the age of 100 years was calculated. As the results of the used equation, site index was strongly (R²=0.58) negatively biased to age, so the bias was removed using an elaborated regression model. For stands older than ca. 20 years, the clear higher site index values as well as higher heights and diameters were found for intra−dune depressions than for slopes of the two studied aspects. This was explained by the occurrence of much more fertile and moister soils in depressions. The only age class for which the advantage of site index and growth parameters was not stated for depressions was the youngest class (≤20 years old). This was likely caused by the competitive impact on young pines of Calamagrostis epigejos which prefers intra−dune depressions on inland dunes and forms in forest floor usually dense cover in this position. Impact of contrasting slope aspect was clearly related in the study to age of a stand. For the youngest studied age class both site index values as well as heights and diameters were lower on north− than on south−facing slopes. This was explained by the effect of weeds which form more dense cover on slopes of this aspect than on sunny slopes. For older stands; however higher site index values as well as heights and diameters were revealed for north−facing slopes, due to pines likely took advantage of higher moisture of soils occurring in this place. With reference to slenderness, regardless stand age the parameter was regularly the highest for north− than both for south−facing slopes and depressions. Because of the revealed distinct higher productivity of intra−dune depressions in normally dry and poor in nutrients dune landscape, it could be reasonable to use the depressions to introduce admixtures of broadleaved tree species into pine monocultures on inland dunes.
The aim of the study was to determine the effect of selected tree stability indices described by individual biometric characteristics on the formation of their wind resistance. The analysis of tree stability was based on easily measurable tree traits, such as height, breast height diameter, crown parameters as well as the centre of gravity and slenderness factor. Investigations were conducted in wind−damaged Scots pine stands, where a total of over 600 trees were measured, of which almost 40% specimens were wind−broken. Results indicate that a significant role in the modification of tree stability is played by the slenderness factor, the location of the centre of gravity and crown parameters. Most of the analysed traits are strongly cross−correlated. However, these are slenderness and crown length that describe tree stability the best.
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