Doctoral thesis, 2010
Regeneration in continuous cover forestry systemsErefur, Charlotta
AbstractThe overall aim of the studies underlying this thesis has been to qualify and quantify the regeneration of tree species in a range of typical growing environments of possible Continuous Cover Forestry (CCF) silvicultural systems in boreal forests of northern Sweden. Data presented in Papers I and II show that the light environment did not differ significantly between points at different distances to trees, but it was clearly affected by the stand stem density (SSD). On a north-facing slope, the emergence rates of direct-seeded seedlings were highest (50 and 44% of germinable Pinus sylvestris and Pices abies seeds, respectively) in a stand with an SSD of 150. In contrast, on a slope with a southern aspect the conditions in SSD 0 favoured emergence of P.sylvestris (41%). For planted P. abies, fertilised seedlings in SSD 0 grew the most (22.2 cm in height on the North and 34.2 cm on the South slope). Establishment of both P. sylvestris and P.abies seedlings was more controlled by the general (light) conditions of the stand than their orientation and distance with respect to the nearest tree. In Paper III, seedling survival and growth were compared between a clear-cut, a multi-layered shelterwood (MLS), and a single-layered shelterwood (SLS). The needle and root biomass of seedlings of both species, growing in identical (good) soil conditions, was highest in the clear-cut (P. sylvestris 63 and 14 g, respectively; P. abies 34 and 12 g, respectively). With those soil conditions, there were also no significant differences in growth, at least for P.sylvestris, between the MLS and SLS, although with increased belowground competition seedlings grew more slowly in the MLS. In Papers IV and V, the establishment and growth of Betula pendula, Populus tremula, P. sylvestris, Larix sibirica, Abies lasiocarpa, and P. abies, planted in a Chequered-Gap- Shelterwood-System (CGSS) with 0.135 ha gaps under a shelter of pine forest, were compared in a 30-year-old (“younger”) stand and a 50-year-old (“older”) stand. Solar radiation transmission in the CGSS was simulated by modelling, and the results of the model were further related to seedling height growth by seedling positions within gaps. In the older stand, it was more favourable for seedlings to grow in south-facing parts of a gap with higher transmission. An approach for estimating biomass based on image inventories was applied, which showed that seedlings generally developed more biomass during the study period in gaps than at edges and in the forest (586.4±93.5 versus 203.8±22.3 and 121.3±24.1 cm² silhouette areas, respectively, in the older stand for example). To conclude, the results from this thesis have shown that tree regeneration and early growth can be maximized in a CCF system by matching growth environments and species, based especially on the considered species’ light tolerance.
Keywordspinus sylvestris; picea abies; betula pendula; populus tremula; larix sibirica; abies lasiocarpa; biomass; selective felling; regeneration; growth; simulation; insolation
Published inActa Universitatis Agriculturae Sueciae
2010, number: 2010:42
Publisher: Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences