The structure and regeneration of high-altitude Norway spruce forests: a review of Arnborg (1942, 1943)

Abstract

The high-altitude forests along the Scandinavian mountain range were relatively unaffected by the first wave of forest utilization and in the mid-twentieth century some untouched forests still remained. In his doctoral thesis, Tore Arnborg analysed the vegetation patterns and forest structure in two mainly primeval forest stands, Blekaskogen and Granudden, in northern Sweden. The sites represent typical spruce-dominated mountain forest, generally not subject to large-scale disturbance by forest fire. Arnborg's studies were among the first giving data on the structure and dynamics of these forests. Both stands were multilayered and of open character. The fraction of mature, overmature and senescent trees was high and about 18% of the trees were considered to be dying. Although having a similar history, the two stands differed in character, mostly owing to the altitudinal difference. Thus, Granudden, situated about 50–80 m above Blekaskogen, had a low canopy and was more open in character. In addition to stand structure, Arnborg analysed tree regeneration. He provided very strong empirical evidence for the important role of dead logs in regeneration. Based on logs of known age, he presented an eight-grade decay classification system, focusing on the possibility of seed germination and survival. A major conclusion from his studies is that the forest is in equilibrium and able to regenerate itself by the periodically high abundance of viable seeds and through the presence of logs and disturbed soil patches. Based on his findings, Arnborg argued for initiating clear-cutting complemented with soil scarification of these high-altitude forests. In his time, just before the onset of the clear-cutting epoch, the focus in forest research was strongly influence by management for increased production.