The study is an attempt to determine variation in the proportions of sapwood and heartwood in the radial and axial sections in stems of common oak (Quercus robur L.), representing the main tree stand (according to Kraft biosocial classification), age classes V (81-100 years) and VI (101-120 years), growing in the fresh mixed forest and fresh forest sites. Sample trees were selected according to Urich I method from four plots (of 1 ha each). For each model tree its crown projection area was determined. After felling all necessary biometric traits of tree stem and live crown were measured. Stems were divided into 2-metre sections, from which centres discs were cut in order to determine selected wood macrostructure parameters and volumes of sapwood rings and heartwood cylinders. Additional discs were cut from breast height and kerf planes of trees. When analyzing results for individual discs and trees arithmetic means of widths (or volumes) of studied wood zones were used. During the study the irregularities were determined of sapwood and heartwood zones in stems. Strong and plus interrelations were found between crown volume and crown projection area (as area of cylinder external surface) and sapwood area at the cross stem section, although some of the correlation coefficients were not significant. Large variation was observed in the proportions of volumes of sapwood and heartwood in individual Kraft‟s biosocial classes. Differences were also found in sapwood and heartwood radial share between age classes, and rather small differences between forest site types.

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