Examples of retention experiments in Finland and Sweden. a Gap felling with 5% group retention inside a gap, spruce forest, third post-harvest summer. DISTDYN project in Finland. Photo: Matti Koivula. b In the Swedish experiment, Effaråsen, Scots pine stands have been harvested with retention levels varying from 3 to 100%. At each level the retention included equal proportions of intact green trees, girdled trees, high-cut trees, and felled trees. In the picture, a level of 30% retention is shown. Photo Line Djupström. c Retention tree group inside a clear-felled area. In the RETREE project, varying sized retention tree groups, 0.1-0.6 ha were left in a harvested area. Photo: Erkki Oksanen/LUKE. d. Naturally regenerated gap in the MONTA experiment 14 years after harvesting. Photo: Erkki Oksanen/LUKE. For more information on the experiments, see Table 2, and for their location, see Fig. 2.