Coarse woody debris legacies and their dynamics in retained forest patches

•Even under exposed surroundings, tree mortality was not severe in retention patches.•Over 20-years, no extreme temporal changes in deadwood occurred.•A diversity of small retention patch types provide long-term supplies of deadwood.•Retaining higher living tree volume during creation generates more post-harvest deadwood.•Over 20-years, downed deadwood increased whilst standing deadwood decreased. Retaining trees in small patches at final harvest is a common forest conservation measure to maintain structural and biological diversity through the young forest phase. Long-term studies of coarse woody debris (CWD, breast height diameter ≥ 10 cm) changes in retention patches remain uncommon, especially in relation to different types of patches with varying tree species composition, ground moisture, size, shape, and exposure. In the present study we re-inventoried CWD three times (1–3, 5–7 and 18–20 years after harvesting) in 60 small tree retention patches (0.03–0.54 ha) of six commonly created retention patch types, in central boreal Sweden. Most retention patch types, despite being very small (