Open access publications in the SLU publication database

Abstract

The objectives of this work were to quantify the effects of stand stem density (SSD), orientation and distance with respect to shelter tree, and fertilisation on the establishment of Pinus sylvestris L. and Picea abies (L.) Karst. regenerated by direct seeding and planting at different soil preparations. The field experiments were performed on South (64°14ʼN, 19°46ʼE, 225 m a.s.l.) and North (64°09ʼN, 19°36ʼE, 274 m a.s.l.) slopes in boreal Sweden. Regeneration and early growth in three stand stem densities (SSDʼs) with different light regimes, i.e. uncut forest (~500 stems/ha), shelterwood (~150 stems/ha),and clear-cut, were compared. Sowing, after using two soil preparations (mineral soil and a mixture of mineral soil and humus layer ground to a fine texture), and planting were done in 2001 at six distances in north-south direction from trees (0.5, 1, 1.5, 2, 4 and 6 meters). Naturally regenerated P. abies seedling and saplings were also selected in pairs in the uncut forest. Half of all seedlings and saplings in the experiments were irrigated with fertiliser (10mM N). The light environment didnʼt differ significantly between different orientations or distances with respect to trees, but it was clearly different between SSDʼs. On the North slope, the emergence of direct seeded seedlings was highest (50 in percent of germinable seeds for P. sylvestris and 44% for P. abies) in SSD 150. On the other hand, on the South slope the conditions in SSD 0 favoured the high emergence of P. sylvestris (41%). Only for P. abies on the North slope, fertilised seeded seedlings were taller (ca. 20%) than nonfertilised seeded seedlings after 4 years. For planted P. abies, the fertilised seedlings in SSD 0 were the ones that grew the most (22.2 cm). Fertilisation had no effect on height growth of planted P. sylvestris, but the growth was clearly increasing (from <20 cm to >50 cm) with decreasing SSD. The naturally regenerated seedlings/saplings in the different height classes showed no response in height growth to fertilisation. With planted P. sylvestris being the more extreme, dry mass of leading shoot in SSD 500 was only 3% of that in SSD 0, while for height growth the corresponding value was almost 30%. The main conclusion was that for plant establishment the general conditions of the stand mattered more than the orientation and distance with respect to the nearest tree and the light environment was more important than the nutritional status, i.e. light requirements could not be moderated by nutrient supply. A resulting new hypothesis was that a system of forest gaps and shelterwood in a geometric pattern could be used in conventional forestry to regenerate forests. This new method of Continuous Cover Forestry (CCF) would benefit from shelter trees while creating the desirable conditions of a clear-cut.