The study was conducted in a 43-ha mixed deciduous forest stand with admixture of conifer trees and with well-preserved old growth structures.

Data describing the long-term successional patterns were gathered from three circular 5000 m² sample plots (radius of 39.90 m).  All trees with DBH (diameter at breast height, 130 cm above the ground) higher than 5 cm were inventoried. Up to a radius of 12.62 m (500 m²), all present tree species were cored with an increment borer as close to the mineral soil as possible (20–80 cm), whereas outside the inner 500 m², only oak, pine, oak and spruce individuals were cored. In total, we cored 275 trees at the ground level (one core per tree). To investigate the early growth of oak, pine, oak and spruce on rich soils of BF and to determine the real ages, 42 trees were randomly selected from the trees cored at the ground level and they were cored additionally at DBH as well.

For the inventory of tree regeneration of other species on a macro-scale, a transect of 25 m length and 2 m width was randomly established in the stand (orientated E-W). All tree regeneration up to 5 cm stem diameter was recorded by species and height. The individuals (48) were collected for age estimation.

The increment cores were dried, glued on wooden mounts and sanded (down to 600 grit) for an easy reading of tree-ring sequences. Under 6–40x magnification, the cores were visually cross-dated by identifying local pointer years following the standard dendrochronological methodology of cross-dating directly on the wood. All developed fire scars found in increment cores and cross-sections were noted (Niklasson & Granström, 2000). Additionally, the disturbances in tree-ring morphology (Niklasson & Granström, 2000) or in the growth pattern were noted and used as a fire record if a certain year was confirmed by a fire scar formed in at least one other sample tree

The samples of seedlings were crosscut at root collar and the surface was sanded and smoothed with a scalpel cut to obtain the clearest possible view of the annual rings.