Seed rain quantity and quality, 1984-1992, in a high altitude old-growth spruce forest, northern Sweden

Short-term regeneration ability of a cold-marginal Picea abies forest was studied by analyzing spruce seed rain during nine years and by assessing resulting recruitment at the end of the studied period. Quantitatively large differences occurred between studied years, and seed viability was low during the whole study period. Only exceptionally did seed viability exceed 1 %. Sparse regeneration occurred in 1984, which is the year when most viable seeds/ha were recorded. In addition, the results are compared with recruitment data from the 1930s (from the same forest), a time period when regeneration peaked. It is suggested that the period 1984-1992, due to the sparse regeneration, retrospectively probably will appear as a regeneration trough or a decreasing regeneration trend. Furthermore, it is concluded that, in a long-term perspective, periodic regeneration is sufficient for maintenance of the forest because of the longevity of spruce. Additionally, climatically induced variations of regeneration success give rise to natural fluctuations in stand density.