Urban Nilsson

Effect of Reforestation Methods on Pine Weevil (Hylobius abietis) Damage and Seedling Survival

Orlander, G.1 and Nilsson, U. (Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Asa Forest Research Station, S-360 30 Lammhult, Sweden and Swedish University of Agricultural Sciences, The Southern Swedish Forest Research Centre, Box 49, S-230 53 Alnarp, Sweden). Effect of reforestation methods on pine weevil (Hylobius abietis) damage and seedling survival. Received Feb. 16, 1998. Accepted Sept. 15, 1998. Scand. J. For. Res. 00: 000-000, 199X. Damage to Norway spruce (Picea abies (L.) Karst.) seedlings by the large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), was monitored in relation to clear - cutting age and silvicultural treatments in southern Sweden. New clear - cuttings were established on four sites during five consecutive years, and seedlings were planted on them from 1989 through 1993. In total, 31 774 seedlings were planted on 20 clear - cuttings. The measures evaluated were seedling insecticide treatment, application of herbicide to gro...

Short- and long-term effects of site preparation, fertilization and vegetation control on growth and stand development of planted loblolly pine

Abstract Short- and long-term effects of high and low site preparation intensity, fertilization at planting and vegetation control on growth and stand development were examined in a study that was established on six sites in southeastern USA. The study was established in 1979–1980, and growth after the 18th growing season is reported. The high-intensive site preparation improved long-term stand volume growth. Evidence suggests that the main long-term effect of the intensive site preparation was a reduction in competition from hardwoods. Herbicide treatment improved seedling establishment and early growth, but growth during the last period of measurements (14–18 years after planting) were lower in the herbicide-treated plots as compared to plots without herbicide treatment when herbicides were combined with intensive site preparation. Fertilization at planting, in combination with high-intensive site preparation, improved volume growth during the first 10 years after planting, while fertilization at planting in combination with low-intensive site preparation had little effect on volume growth. The hypothesis that low variability in the seedling stage due to intensive site preparation will lead to low variability in the mature stands with a subsequent reduction in self-thinning was examined. The low site preparation intensity had higher coefficient of variations of stem volumes, and higher mortality. However, the difference in mortality was probably partly a result of differences in competition from hardwoods, and it was not possible to separate the importance of reduced variability from reduced competition from hardwoods. Fertilized plots had lower variability than non-treated control plots but there was no significant difference in mortality between the two treatments. Therefore, it was concluded that reduced variability in the seedling stands, as a result of intensive regeneration methods that reduces environmental heterogeneity, reduces the variability in the mature stands. However, it could not be inconclusively proved that lower variability in the mature stands will result in reduced or postponed self-thinning.

Natural regeneration of Norway spruce, Scots pine and birch under Norway spruce shelterwoods of varying densities on a mesic-dry site in southern Sweden

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 6 year period. The shelterwood densities ranged from 277 to 96 stems/ha 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.

Pine weevil abundance on clear‐cuttings of different ages: A 6‐year study using pitfall traps

Patterns of seasonal and yearly variation in the abundance of the pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), were determined on clear‐cuttings of various age in southern Sweden. New clear‐cuttings were established during each of five consecutive years, and the numbers of weevils caught in pitfall traps baited with α‐pinene and ethanol were recorded weekly during the season for up to 6 yrs on these areas. In total, 74 281 weevils were trapped. On fresh clear‐cuttings, the catches increased drastically once migrating weevils had arrived in spring. Catches peaked in May and July but were lower in June, when oviposition underground is most intense. The catches declined suddenly in the middle of August, coincident with the weevils becoming post‐reproductive. On older clear‐cuttings, most weevils were caught before migration in spring; thereafter the catches gradually decreased from June to September. Pine weevils were even abundant on 5‐yr‐old clear‐cuttings. Relationships between trap cat...

Productivity of needles and allocation of growth in young Scots pine trees of different competitive status

Abstract It has been suggested that the allocation of carbon to stem wood growth has low priority, and that productivity of needles (above-ground tree biomass increment per unit leaf weight) decreases as competition between trees increases. To test this, carbon allocation to different growth components and productivity of needles were compared between trees of different tree classes (dominant, codominant, intermediate and suppressed). The study was carried out in two 16-year-old Scots pine (Pinus sylvestris L.) stands, planted at different initial densities: 40 000 and 10 000 seedlings ha−1. It was found that the allocation of carbon to stem wood production, and probably also fine root production, has high priority for trees under hich competitive stress. It was also found that production per unit weight of needles increases with competition; at least for as long as the trees are experiencing approximately the same light regime.

Development of oak and beech seedlings planted under varying shelterwood densities and with different site preparation methods in southern Sweden

Effects of site preparation, shelterwood density and planting depth on the survival and growth of planted beech and oak seedlings were studied. Experiments were performed in one oak and one beech stand in southern Sweden. Two areas with different densities of shelterwood and one clearcut were established in each stand. Growth, damage and survival of the planted seedlings were observed for three years. Soil water potential was recorded weekly and radiation and soil temperatures were recorded continuously during the growing seasons.Neither site preparation methods nor planting depth affected oak seedling growth, when planting was carried out on fresh clearcuts or in shelterwoods, while growth of beech seedlings was positively affected by mounding. Growth of oak seedlings was inhibited by the shelterwood treatments. In beech seedlings, growth was lowest in dense shelterwood, while there was no difference in growth between seedlings on the clearcut area and in the shelterwood of low density. Differences in growth may be explained by differences in radiation and soil water potential.When planting was carried out on a one-year-old clearcut, site preparation improved the subsequent growth of oak and beech seedlings.

The effects of shelterwood density and site preparation on natural regeneration of Fagus sylvatica in southern Sweden

Abstract The natural regeneration of beech (Fagus sylvatica) was studied under various shelterwood densities and soil preparations in a 130-year-old beech stand in southern Sweden. Between 1990 and 1996, seedling emergence, survival, growth and damage were followed in a clear-cut and in two shelterwoods with different densities, in plots with undisturbed ground, bare mineral soil or ridges with mineral soil on top of humus. Irradiation, soil and air temperatures, soil moisture and precipitation were continuously recorded during the first three growing seasons. The seedling emergence was higher in the shelterwoods than in the clear-cut. The mortality was the highest during the first year. The seedling number was the highest on bare mineral soil and the lowest on undisturbed ground, for all cutting regimes. The increase in seedling height and dry mass was greater in the clear-cut and in the sparse shelterwood than in the dense shelterwood. Damage due to frost was more frequent in the clear-cut than in the shelterwoods. Effects of most kind of damage had only minor influence on the seedling height, whereas in seedlings experiencing frequent damage height was reduced.

Reforestation with planting in northern Europe

Abstract This paper reviews regeneration research during the past 20 years. The focus is mainly on planting of Norway spruce and Scots pine. Research on root morphology and nursery practices has played an important role in the introduction of containerized seedlings in northern Europe. In recent years, mini-seedlings have been tested. Conventionally, seedlings are planted in spring and early autumn but recent research indicates that Norway spruce seedlings can be planted from spring until the end of September. Soil temperature strongly influences seedling establishment in the harsh northern Scandinavian climate and a good way to increase soil temperature is to plant in elevated planting spots, which can be achieved by mounding. Soil scarification also reduces competition from field vegetation and damage by pine weevils. In southern Finland, Sweden and Norway, pine weevils are by far the most serious causes of damage to both Norway spruce and Scots pine. Therefore, designing regeneration treatments for decreasing pine weevil damage without using insecticides is one of the more important current research challenges. Examples of possible future trends in forest regeneration research are an emphasis on more basic research, use of fast growing tree species, multidisciplinary approaches and site-specific regeneration regimes.

Scarification and seedfall affects natural regeneration of Scots pine under two shelterwood densities and a clear-cut in southern Sweden.

A study was undertaken to evaluate the effect of Scots pine (Pinus sylvestris) shelterwood density and timing of removal on the regeneration of forests with improved wood quality. This paper focuses on the effect of scarification and seedfall on the success of natural regeneration of Scots pine under two shelterwood densities and in a clear-cut. Wood quality aspects will be addressed later in the study. After 4 yrs, natural regeneration of Scots pine under a 200 stems ha-1 shelterwood reached 90000 seedlings ha-1, 53000 under a 160 stems ha-1 shelterwood and 3700 in a clear-cut. The high natural regeneration under the densest shelterwood resulted from a high seedfall, slower invasion by competing vegetation, consequent prolonged recruitment and low mortality. Since mortality largely decreased for both shelterwood densities and recruitment seems to continue, the success of regeneration should be maintained in the future if proper release operations are conducted. The latter could begin when seedlings reach a height of about 0.5 m and the cover should be maintained until they reach a height of about 6 m. Therefore, it may be possible to use 200 stems ha-1 Scots pine shelterwoods in southern Sweden to obtain dense stands and thus improve wood quality (stem taper, wood density, etc.).

Germination and early growth of sown Quercus robur L. in relation to soil preparation, sowing depths and prevention against predation.

A field experiment was established in the autumn of 1992 in order to study predation of acorns, germination and early growth of oak seedlings. The experiment was established on a clearcut and an adjacent oak shelterwood in southern Sweden. In the experiment, a total of 6 840 acorns were sown. The sowing was carried out with different vegetation control and soil preparation treatments and with different planting depths.The germination percentage was highest for acorns sown at five cm depth and lowest for acorns sown on top of the soil, and lower for acorns sown in areas where the humus layer had been removed than in areas where the humus layer was retained. There was no difference in the percentage germination after two growing seasons between acorns sown inside the shelterwood and acorns sown on the clearcut. The height of the seedlings was lowest when the humus was removed while the number of leaves per seedling was lowest for seedlings in untreated areas after two growing seasons. Furthermore, seedlings in untreated areas showed the lowest relative height growth rate during the second growing season. In spite of higher biomass of ground vegetation in undisturbed areas compared to treated areas, no effect of the soil and vegetation control treatments could be found on soil water potentials. The soil temperature and photosynthetic active radiation at seedling level were higher in areas where soil preparation and vegetation control had been performed. However, it was concluded that neither low soil water availability nor low light levels could be the only cause of lower relative height growth rate during the second growing season for seedlings in undisturbed areas.