STRUCTURE OF A PRISTINE PICEA-ABIES FOREST IN NORTHEASTERN EUROPE

The forest structure in a large, relatively homogeneous area of pristi ne Picea abies taiga in the southern boreal region west of the Ural mo untains was studied along four 500-m long transects. P. abies dominate d the forest in association with Abies sibirica and Betula spp. The me an volume of living trees was 216 m(3)/ha. This value varied among the four transects, from 138 - 252 m(3)/ha. Mean density of trees (DBH > 1 cm) (and variation over the transects) was 2064/ha (1670-2710). Livi ng 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 compon ent and made up 16 % of the living tree volume. The number of dead sta nding trees varied from 195 - 325ka, corresponding to a volume of 10.8 - 70.7 m(3)/ha. The density of trees with a broken stem was 90 - 170/ ha and their estimated volume 7.6 - 41.3 m(3)/ha. Standing dead trees and trees with broken stems represented 10.4 and 8.9 % of the total st anding tree volume (living + dead), respectively The mean volume of de caying logs on the forest floor was 117 (84.4-156.2) m(3)/ha, correspo nding to 54 (35 - 113) % of the living tree volume. The canopy-fonning trees were present in the understory as abundant saplings and suppres sed individuals. The size distribution of the dominant tree species re sembled the inverse J-shape. Generally, the forest was characterized b y 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 stage s of recovery following disturbance. Our results suggest that the ecol ogy and dynamics of extensive areas of natural boreal forests can be d riven by small-scale disturbance.