Development of an 80-year-old mixed stand with retained Pinus sylvestris in Northern Sweden

Abstract

Retention of live and dead trees in harvested stands has become a common practice in Scandinavian forestry. We examined how retained Scots pines ( Pinus sylvestris L.) grow and to what extent they compete with the new generation. In a mixed stand of about 5 ha in Northern Sweden, 44 retained pines and adjacent growth of the new stand was measured for the last 90 years. After liberation in 1912, the pines, then with a mean age of 180 years, doubled their annual ring width to a culmination after about 30 years. The trees below mean height showed the biggest response to liberation. The lower part of the stem (0.5–1.3 m) showed the largest growth relative to the decade before release during the first two decades after release. In the last decade the relative growth was largest at 6 m height. Growth of the new generation was measured on 9.5 m radius plots, centred on the retained pines. The growth of the new stand was reduced by 20% in the inner third of the plot area. With 10 evenly dispersed retained pines per hectare the production loss in the new generation was estimated at 2.5% over one rotation. The growth of retained trees more than compensated for this loss. The volume of the new stand was positively correlated with retained tree size and negatively correlated with retained tree growth. Of 17 species and species groups identified in the forest floor vegetation, only lichen occurrence correlated with distance to retained trees. Lichen was more common close to small and fast-growing retained trees.