Current issue: 56(4)
Under compilation: 57(1)
Mechanical site preparation (MSP) is a common practice that precedes the planting of Norway spruce (Picea abies (L.) H. Karst.) in Nordic forests. Mounding has become the most used method in spruce planting in recent years. This study examined the effects of different mounding treatments (spot and ditch mounding, inversion, unprepared control with or without herbicide application) and a mechanical vegetation control (MVC) treatment done 3–4 years after planting on the post-planting growth of spruce container seedlings and their development to saplings during the first 11–13 years on two forest till soils in central Finland, one on flat terrain and other on a southwest slope. On these fine-textured soils the spot and ditch mounding methods favoured spruce saplings development. Inversion and unprepared plots showed weakest growth. On the site with flat terrain, 11 years post planting, spruce saplings were 78–144 cm (38–80%) taller and their breast height diameters were 11–13 mm (60–74%) thicker for ditch or spot mounding than for inversion or herbicide treatment. On the site with sloped terrain the differences were minor between the MSP treatments. MVC improved spruce height growth on sites which did not have intensive MSP, especially on control saplings planted on unprepared soil in herbicide and inversion treatments. On the flat terrain, MVC reduced the density of resprouts to be removed later in pre-commercial thinning. As a conclusion, spot or ditch mounding favoured the growth of spruce over inversion especially on flat terrain with fine-textured soil.
Mechanical site preparation methods that used tools mounted on lightweight excavators and that provided localised intensive preparation were tested in eight experimental sites across France where the vegetation was dominated either by Molinia caerulea (L.) Moench or Pteridium aquilinum (L.) Kuhn. Two lightweight tools (Deep Scarifier: DS; Deep Scarifier followed by Multifunction Subsoiler: DS+MS) were tested in pine (Pinus sylvestris L., Pinus nigra var. corsicana (Loudon) Hyl. or Pinus pinaster Aiton) and oak (Quercus petraea (Matt.) Liebl. or Quercus robur L.) plantations. Regional methods commonly used locally (herbicide, disk harrow, mouldboard plow) and experimental methods (repeated herbicide application; untreated control) were used as references in the experiments. Neighbouring vegetation cover, seedling survival, height and basal diameter were assessed over three to five years after plantation. For pines growing in M. caerulea, seedling diameter after four years was 37% and 98% greater in DS and DS+MS, respectively, than in the untreated control. For pines growing in P. aquilinum, it was 62% and 107% greater in the same treatments. For oak, diameter was only 4% and 15% greater in M. caerulea, and 13% and 25% greater in P. aquilinum, in the same treatments. For pines, the survival rate after four years was 26% and 32% higher in M. caerulea and 64% and 70% higher in P. aquilinum, in the same treatments. For oak, it was 3% and 29% higher in M. caerulea and 37% and 31% higher in P. aquilinum. Herbicide, when applied for three or four years after planting, provided the best growth performances for pines growing in M. caerulea and P. aquilinum and for oaks growing in P. aquilinum. For these species and site combinations, DS+MS and DS treatments reduced the neighbouring vegetation cover for one to four years following site preparation.