Structure of a pristine Picea abies forest in northeastern Europe

Abstract. The forest structure in a large, relatively homogeneous area of pristine Picea abies taiga in the southern boreal region west of the Ural mountains was studied along four 500-m long transects. P. abies dominated the forest in association with Abies sibirica and Betula spp. The mean volume of living trees was 216 m³/ha. This value varied among the four transects, from 138 - 252 m³/ha. Mean density of trees (DBH > 1 cm) (and variation over the transects) was 2 064/ha (1670 - 2710). Living trees classified as dying or seriously damaged made up 2.9 (2.5 - 3.5) % of the living tree volume. Betula was an important canopy component and made up 16% of the living tree volume. The number of dead standing trees varied from 195 - 325/ha, corresponding to a volume of 10.8 - 70.7 m³/ha. The density of trees with a broken stem was 90 - 170/ha and their estimated volume 7.6 - 41.3 m³/ha. Standing dead trees and trees with broken stems represented 10.4 and 8.9% of the total standing tree volume (living + dead), respectively. The mean volume of decaying logs on the forest floor was 117 (84.4–156.2) m³/ha, corresponding to 54 (35 - 113) % of the living tree volume. The canopy-forming trees were present in the understory as abundant saplings and suppressed individuals. The size distribution of the dominant tree species resembled the inverse J-shape. Generally, the forest was characterized by a high small-scale structural variation and a larger-scale relative homogeneity. This pattern is consistent with forest dynamics where the forest consists of a small-scale mosaic of patches in different stages of recovery following disturbance. Our results suggest that the ecology and dynamics of extensive areas of natural boreal forests can be driven by small-scale disturbance.