Morphological adaptation of the root system of silver fir responding to changes of local environmental conditions

The study aimed to verify allometric changes in the root system structure of nearly 100-year-old silver fir ( Abies alba Mill.) growing in Białowieża Forest. Traditional views of this species as possessing a simple taproot with 4–5 strong diagonal roots required supplementation with evidence of significant modification under specific conditions. It was observed that it developed extensive lateral root networks reaching 41.8–44.2 m diameter in the upper soil profile, exceeding previously reported maxima (21.2 m). This resulted from reduced competition after Norway spruce ( Picea abies (L.) H.Karst) mortality due to drought, low groundwater level, and bark beetle infestation. The allometric shift in favor of lateral roots shows significant plasticity despite advanced age. The results confirm the climax nature of the species and show that the studied species has significant morphological adaptation. Remarkable are the significant spatial parameters (especially horizontal) of the distribution of the thin roots in the horizon of soil parent rock: depth 1.95–2.40 m, distance from the tree 6.40–10.38 m.They belong to a flattened bundle of roots growing parallel to the soil surface from the tip of the taproot and diagonal roots. Root systems were examined using ground-penetrating radar and traditional excavation methods combined with soil coring. Root identification relied on distinctive visual characteristics and anatomical analysis.