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The aim of the research was to determine the habitat−related variation in the selected structural and physical− −mechanical properties of silver birch. Two sample plots were established in the territory of the Biała Podlaska Forest District in eastern Poland. Samples for measurement were taken from the plots with trees aged 45−50 years growing in the fresh deciduous (Lśw) and fresh mixed deciduous (LMśw) forest habitats. The following properties were subjected to statistical analysis: the average width of annual rings, wood density determined for the samples of 20×20×300 mm, 20×20×30 mm, and 30×2.66×0.1 mm in size (the last dimension parallel to grain), tensile strength parallel to grain, compression strength parallel to grain, static bending, modulus of elasticity in static bending and the coefficients of tensile strength parallel to grain, compression parallel to grain, static bending, and modulus of elasticity in static bending. The research confirmed a significant effect of the habitat on the mean values of birch wood density for all examined sample sizes, tensile strength parallel to grain, static bending and modulus of elasticity in static bending. No significant effect of the habitat on the mean values of annual ring width, tensile strength parallel to grain and the coefficients of tensile strength parallel to grain, compression strength parallel to grain, static bending and modulus of elasticity in static bending for birch wood samples was found.
The paper presents the study on the height of 10−12−year−old pedunculate oak regeneration in clear−cut gaps in three fertility variants: mezotrophic of poorer productivity (fresh mixed coniferous forest – BMśw), mezotrophic of higher productivity (fresh mixed deciduous forest – LMśw) and eutrophic (fresh deciduous forest – Lśw). BMśw and LMśw were represented by two locations: Gostynin (G) and Parczew (P), while Lśw – by one: Czarna Białostocka (CzB). We analysed the variation of oak height in the patches along the north−south (N−S) and east−west (E−W) gap axes. In each location 3−5 gaps were selected and measurements taken on three transects along the N−S axis located in the western (W), central (C) and eastern (E) part. Significant differences in oak height were found along the N−S axis. Oaks in the BMśw and LMśw habitats in the south−central part, and those in the Lśw habitat in the centre−northern part of the patch were the highest. The height growth of oaks on sandy soils (BMśw, LMśw) was found to be limited by moisture deficit, while on loamy soils (Lśw) – by light deficiency. The differences in oak height along the E−W axis were smaller and less apparent, indicating a tendency towards the reduction of their height growth in the central part of the gap.
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