Table 5. Number of naturally regenerated seedlings (mainly birch) per hectare following each mechanical site preparation method (MSP, i.e. disc trenching, mounding, soil inversion and patch scarification) and No MSP. The total area column presents densities in the whole regeneration areas, both affected and not affected by MSP. The affected area column presents densities for different MSP methods only in the area disturbed by the MSP. Data from field experiments and surveys of stands established in operational forestry, recorded 3–14 growing seasons after planting.
Tree species Years after planting Total area Affected area No. of
sites 		Location, Reference
No MSP Disc trenching Mounding Inverting or
Patch scarification 		No MSP Disc trenching Mounding Inverting or
Patch scarification
Birch 3 4700–15 100 ~4500 – ~16 000 ~4000 – ~12 000 ~9500 – ~10 000 18 Southern Finland Lehtosalo et al. (2010)1
Birch 5 ~5000 ~6000 13 900 (furrow) 2900 (berm) 1 Southern Sweden Nilsson et al. (2002)2
Birch 5 3000 19 400 4 Southern Sweden Karlsson et al. (2002)3
All species 5 12 000–19 000 5000–15 000 2 Southern Sweden Holmström et al. (2016)4
Birch 5–8 14 400 6100 8 Southern Sweden Karlsson and Nilsson (2005)5
Birch 6 8500–16 100 ~6000 – ~13 000 ~20 000 – ~35 000 ~14 500 – ~23 000 18 Southern Finland Lehtosalo et al. (2010)1
All species 7 22 570 14 490 1 Central Finland Uotila et al. (2010)6
Broad-leaves 5–8 ~2500 – ~8000 ~4000 – ~14 000 22 Southern Sweden Nilsson et al. (2006)7
Birch 9 6800–9600 ~4000 – ~6000 ~25 000 – ~28 000 ~10 500 – ~17 500 18 Southern Finland Lehtosalo et al. (2010)1
All species 14 921 2151 2136 10 Sweden Johansson et al. (2013a)8
1 Survey study (chronosequence) of clearcuts of different ages (three, six and nine years after mounding and planting) of Norway spruce seedlings. In total 18 sites in Finland (Lat 60.5–62°N), nine of Myrtillus and nine of Oxalis-Myrtillus vegetation types.
2 One trial at Tönnersjöheden (56°40´N); dry to mesic soil; coarse/sandy texture and sandy-silty till; site index for spruce 30 m (upper height at 100 years).
3 Four sites close to Tönnersjöheden (56°20´N) and Asa (57°08´N); fertile soils. At Asa mesic moist sandy till, site index for spruce 28 m. At Tönnersjöheden dry till with coarse texture, site index 31 m for spruce.
4 Two sites in southern Sweden; Kronoberg and Halland, four blocks in Kronoberg with disc trenching or inverting and three blocks in Halland with disc trenching or no site preparation.
5 Eight sites in southern Sweden; three with patch scarification and five with disc trenching; seven mesic sites, Vaccinium myrtillus and one dry, Carex ssp. vegetation types. Site indices for pine, 22–26 m.
6 One site in central Finland (Suonenjoki). Number of stems removed during pre-commercial thinning.
7 Twenty-two sites in Sweden – eight in northern, eight in central and six in southern Sweden (site indices, 20–24, 23–26 and 18–28 m, respectively). Mainly mesic soils and sandy-silty tills, but one dry site and two with silty clays. Vaccinium ssp. or Carex ssp. vegetation types.
8 Ten sites in Sweden along north-south cline (lat. 57 to 65°N). Site indices 16–32 m. All naturally regenerated stems above 1.3 m in height included, mainly broadleaves.