Effects of thinning and extraction on advance regeneration of Sitka spruce (Dartmoor 2005)

Extensive damage to and mortality of understorey seedlings during overstorey thinning could prevent the use of natural regeneration as a method of restocking. Experiments carried out on three upland conifer sites in Britain assessed the short-term impact of thinning operations on survival and damage to advance regeneration seedlings of different heights. At two sites dominated by Sitka spruce, the number of small-sized (<50 cm) and medium-sized (50 – 200 cm) seedlings lost during harvesting was significantly higher than the number of large seedlings (>200 cm) which tended to be damaged rather than lost. At the Scots pine/Japanese larch site, damage and loss were not related to seedling size. Survival or damage was significantly related to the distance from the nearest extraction rack (striproad). At two of the sites, survival or damage was related to distance to the nearest felled tree stumps. The seedlings in 25 – 30 per cent of the area were lost due to clearing the extraction racks prior to harvesting. In the stand matrix, 40 – 80 per cent of the regeneration survived and was not severely damaged; the remaining regeneration was likely to be suffi cient to restock at all three sites, although distributions were clumped. There were no marked differences between motormanual and harvester felling. See also: Stokes, V., Kerr, G., and Ireland, D. (2009.) Seedling height and the impact of harvesting operations on advance regeneration of conifer species in upland Britain. Forestry. 82 (2): 185-198. (see pdf) Attribution statement: