Natural regeneration of Norway spruce, Scots pine and birch under Norway spruce shelterwoods of varying densities on a mesic-dry site in southern Sweden
Urban Nilsson, Pelle Gemmel, Ulf Johansson, Matts karlsson & Torkel Welander
The effects of shelterwood density and site preparation on the emergence, survival and growth of naturally regenerated Norway spruce (Picea abies L. Karst.), Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth. and B. pubescens Ehrh.) seedlings were investigated in Norway spruce shelterwoods in southern Sweden over a six-year period. The shelterwood densities ranged from 277 to 96 stems per hectare and an adjacent clear-cut. Scarification increased the emergence of all species. Increased shelterwood density promoted the emergence of Norway spruce seedlings, while the emergence of Scots pine and birch seedlings were not significantly affected by the shelterwood density. The survival of birch was negatively correlated to increased shelterwood density, while the survival of Norway spruce and Scots pine were less affected. Soil scarification had no significant effect on the survival of Scots pine and birch. In Norway spruce, the survival was higher in mineral soil than in undisturbed soil. Seedling growth decreased with increased shelterwood density for all species. Removal cutting of shelterwoods produced a high mortality in Norway spruce and Scots pine, but not in birch. The Norway spruce seedlings were evenly distributed throughout the shelterwood, whereas Scots pine and birch seedlings appeared in patches. Findings from this study indicate that a mixed-species forest may be established by using the following natural regeneration method: a sparse shelterwood, combined with scarification. Then, the future tree species mixture can be controlled through pre-commercial thinning and, if necessary, by complementary planting.
Jonas Bergquist, Göran Örlander & Urban Nilsson
AbstractIn a large field experiment we studied the influence of regeneration management on the extent to which roe deer (Capreolus capreolus L.) browse on spruce (Picea abies L. Karst) seedlings. Our objectives were to evaluate if good post planting seedling management may increase browsing damage by deer. Data was collected between 1993 and 1995 and in the winters of 1993-94 and 1994-95 the frequency of browsed seedlings was 13.2 % and 13.6 % respectively. The frequency of browsing damage varied considerably between sites and clearcuts. Browsing damage was more frequent when the regeneration methods included insecticide treatments. Among insecticide-free treatments, browsing was heavier on scarified plots than on herbicide-treated or control plots (in which seedlings were planted on untreated ground and given no post-planting treatment). Containerised seedlings were browsed more than bare-rooted ones. Neither the age of clearcut when planting, nor removal of slash, had any effect on browsing. It was demonstrated that regeneration methods that increased plant vigour (as assessed by leader growth and needle colour index) led to more browsing damage. Thus, our results support the plant vigour hypothesis, which states that many herbivores prefer to feed on vigorous plants because they are more nutritious. However, plant vigour does not appear to have been the strongest factor affecting the browsing of containerised versus bare-rooted seedlings.
of young Norway spruce (Picea abies L. Karst) to winter browsing by roe deer
Jonas Bergquist, Roger Bergström & Andrew Zakharenka
The effect of natural and simulated roe deer browsing
on mortality, growth and development of technical defects on young recently
planted Norway spruces was studied in two field studies and one experiment. No
negative effect of browsing or clipping on mortality was observed. Height growth
was reduced with the number of years with browsing or clipping and three years
of browsing or clipping appear to reduce growth with about one year. Spruces
frequently became multi-trunked and/or with multiple leaders as long as browsing
and clipping lasted. However when browsing or clipping ceased, almost all
spruces became single-trunked again. The remaining effect of the early
multi-trunking was an increased level of large abnormal branches
“spike-knots” and most of them was located around 40-50 cm up on the trunk.
The characteristics of the spike knots resulting from browsing and clipping were
not different from such originating from other causes of damages.
of newly planted Norway spruce seedlings to fertilisation, irrigation and
Nilsson and Göran Örlander
The effect of
herbicide, fertilisation and irrigation treatments on growth of planted Norway
spruce seedlings were investigated in an experiment established in 1998 in
southern Sweden. After three years, the amount of ground vegetation was about
the same in fertilised, irrigated and fertilised+irrigated plots, but the amount
was about double as in the control. Seedling growth was positively affected by
the herbicide treatment. Fertilisation increased growth when it was combined
with herbicides. Irrigation did not have any significant effect on seedling
growth. Results from this study indicate that competition for water between
ground vegetation and planted Norway spruce seedlings is of little importance.
However, this conclusion is restricted to seedling growth during years with at
least normal precipitation. It was also indicated that increased nutrient
availability is positive for seedling establishment and growth, but that the
planted seedlings were not growing at their potential even when herbicide,
irrigation and fertilisation treatments were combined indicating establishment