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Successful stand regeneration is one of the keystone elements of sustainable forest management. It ensures that ecosystems submitted to stand-replacing disturbances return to a forested state so that they can maintain the provision of wood fiber, biodiversity, carbon sequestration, and other ecosystem services. This chapter describes how plantation forestry, including tree breeding, and novel tools, such as genomic selection, can support the sustainable management of boreal forests in the face of climate change by, among other benefits, reducing management pressure on natural forests and favoring ecosystem restoration.

Damage to planted conifer seedlings caused by the pine weevil Hylobius abietis (L.) is a severe and persistent threat to successful forest regeneration in Europe. Various countermeasures are available, which vary in effectiveness, costs and environmental impact, but none are ideal for all situations. Therefore, there is strong interest in robust assessments of damage risks, as they would enable more cost-effective and environmentally friendly forest pest management. It has been suggested that numbers of adult pine weevils caught in host-odour baited traps placed in regeneration sites may be valuable in such risk assessments. However, published studies provide at most weak support for the hypothesis that trap catch data provide adequate predictions of damage. Therefore, we conducted a two-year field study, designed to determine the relationship between weevil trap catch and subsequent damage at 10 regeneration sites in central Sweden. Site factors that might influence pine weevil feeding on seedlings were recorded and used as explanatory variables in the analysis. Stoniness was the only site factor identified as having a significant effect; damage mainly increased with increases in stoniness. No significant correlation was detected between damage to planted conifer seedlings and numbers of pine weevils trapped in the same locations. We suggest that this lack of correlation between weevil numbers and damage is due to planted seedlings only constituting a minor part of the weevils food intake and considerable between-site variation in availability of food sources other than seedlings. Therefore, assessment of pine weevil numbers appears unlikely to be useful for predicting damage risk at specific regeneration sites.

Various site preparation methods are used in Swedish forestry. However, some methods can lead to unnecessary disturbance, which could be avoided by using variables from digital elevation models in management decisions. The current study aimed to investigate how different site preparation methods, and their intensities, affect Norway spruce (Picea abies (L.) Karst.) regeneration. Additional aims were to clarify how these methods affect soil disturbance and vegetation development, along with how variables from digital elevation models could be used in silvicultural decision-making. Experimental sites were established in southern Sweden to assess five different site preparation treatments with different planting densities: (1) conventional disc trenching 2500 seedlings/ha (DT2500); (2) low intensity disc trenching 1250 seedlings/ha (LDT1250); (3) low intensity disc trenching 2500 seedlings/ha (LDT2500); (4) low-intensity patch-wise 1250 seedlings/ha (PW1250); and (5) patch-wise 2500 seedlings/ha (PW2500). Site preparation intensity had no effect on seedling growth and, survival or vegetation development; the tested treatments differed in terms of soil disturbance. Planting spot properties and weather conditions influenced the seedling performance. DTW and slope could not substantially explain either seedling growth or survival. The results indicate that the choice of site preparation method should consider flexibility when planting while adapting the level of disturbance accordingly.

Norway spruce (Picea abies (L.) H. Karst) and Scots pine (Pinus sylvestris L.) have different site preferences, but silvicultural recommendations for their regeneration at planting (includi...

In the Nordic countries Finland, Norway and Sweden, the most common regeneration method is planting after clearcutting and, often, mechanical site preparation (MSP). The main focus of this study is to review quantitative effects that have been reported for the five main MSP methods in terms of survival and growth of manually planted coniferous seedlings of Norway spruce ( (L.) Karst.), Scots pine ( L.) and lodgepole pine ( var. Engelm.) in clearcuts in these three countries. Meta analyses are used to compare the effects of MSP methods to control areas where there was no MSP and identify any relationships with temperature sum and number of years after planting. In addition, the area of disturbed soil surface and the emergence of naturally regenerated seedlings are evaluated. The MSP methods considered are patch scarification, disc trenching, mounding, soil inversion and ploughing. Studies performed at sites with predominately mineral soils (with an organic topsoil no thicker than 0.30 m), in boreal, nemo-boreal and nemoral vegetation zones in the three Fenno-Scandinavian countries are included in the review. Data from 26 experimental and five survey studies in total were compiled and evaluated. The results show that survival rates of planted conifers at sites where seedlings are not strongly affected by pine weevil ( L.) are generally 80–90% after MSP, and 15–20 percent units higher than after planting in non-prepared sites. The experimental data indicated that soil inversion and potentially ploughing (few studies) give marginally greater rates than the other methods in this respect. The effects of MSP on survival seem to be independent of the temperature sum. Below 800 degree days, however, the reported survival rates are more variable. MSP generally results in trees 10–25% taller 10–15 years after planting compared to no MSP. The strength of the growth effect appears to be inversely related to the temperature sum. The compiled data may assist in the design, evaluation and comparison of possible regeneration chains, i.e. analyses of the efficiency and cost-effectiveness of multiple combinations of reforestation measures.Picea abiesPinus sylvestrisPinus contortalatifoliaHylobius abietis

Biomass from forestry is one of the largest components of Sweden’s renewable resources. Poplars are currently the highest producing tree species available and are therefore natural choices for biomass-oriented production. Growing poplars has been of most interest on agricultural land, but the knowledge and experience about their cultivation is still limited. Factors that have a large impact on the regeneration results are plant material, competing vegetation, browsing and damage caused by voles or climatic factors. Due to large establishment costs, there is a need to find methods to secure the establishment both biologically and economically. In this study the effect of plastic mulch in combination with three different plant types (short cuttings, long cuttings and rooted plants) were tested at three different sites. Five years after planting, the overall effect of mulch was an improved plant survival and growth. In most cases, long cuttings outperformed short cuttings and rooted plants. Clonal differences were present, indicating the importance of using plant material adapted to site conditions. All sites were heavily affected by browsing and during the experimental period 100% of the plants were damaged at some point. Planting poplars without fencing is therefore doubtful. Results from this study conclude that poplars can be established with success on agricultural land if proper measures are used depending on the site to be planted.

In northern Europe, there are high risks of severe pine weevil (Hylobius abietis) damage to newly planted conifer seedlings. Site preparation is one of the most important measures for reducing these risks and as several studies have shown the damage is highly dependent on the amount of pure mineral soil around the seedlings. We investigated effects of three site preparation techniques: (1) disc trenching with a conventional Bracke T26, (2) MidiFlex unit and (3) soil inversion with a Karl Oskar unit on characteristics of the planting spots, growth and pine weevil damage and survival rates of untreated and insecticide treated planted Norway spruce (Picea abies) seedlings. All three site preparation techniques reduced pine weevil damage in comparison with no site preparation, and the proportion of spots with pure mineral soil they created was inversely related to the rate of mortality caused by pine weevil. The results indicate that the quality of the planting spots depends on the technique used. In areas where pine weevil is the major threat to seedling survival, the amount of mineral soil in the planting spots is the most important factor in order to protect the seedling from damage. Without site preparation most planting spots consisted of undisturbed humus. Generally, the Karl-Oskar created the most spots with pure mineral soil, but on very stony soils the Bracke T26 created more mineral soil spots than other methods. Site preparation is a valuable tool in order to improve survival in regeneration areas and it is of great importance to make the right choice of technique depending on the particular circumstances on the actual site.

In the establishment phase, several management alternatives could be applied that affect the species composition of the future stand. In this study, tree seedling data from experiments with planted Norway spruce (Picea abies L. Karst) and naturally regenerated species, mainly Silver birch (Betula pendula Roth), were used for six simulated pre-commercial thinning (PCT) scenarios. The scenarios included both monocultures and mixed stand alternatives with various initial spacing of the planted Norway spruce (0, 1600 or 2800 seedlings) and selection of main stems based on relative heights. Further stand development and individual tree growth were simulated until final harvest. Potentially, based on findings of the seedling measurements, the stands could be mixed with five to six species, but the browsing pressure from ungulates reduced this possibility since the height growth for all species except Norway spruce was highly affected by browsing. The simulated mixtures had a small variation between the PCT scenarios for the maximum mean annual increment (about 10 %). Although the growth was similar for Norway spruce, the proportion of birch in the final stands differed from 3 to 21 % between treatments and none of the high-density planting treatments generated a mixed Norway spruce–birch forest at the time of final felling.

The interest for fast growing poplar species has increased, but the establishment on forest soils can be disappointing. One explanation could be low pH-levels. Thus, the main purpose of this study was to test the development of available poplar clones on soils with different soil acidity. The study was divided into two parts. In study A, poplar cuttings were planted in peat soil with pH-levels ranging from 3.4 to 5.7. In study B, the same plant material was planted in forest soils collected from different sites with different pH levels. Both studies were carried out in a greenhouse. Soil acidity had a significant effect on plant development. With increasing pH, height and biomass of the poplar clones increased. A difference in allocation between root and aboveground biomass was seen among treatments with more biomass directed above ground at higher pH. This pattern was more pronounced with increasing plant weight. Less Al and more Ca were found in leaves from plants grown in soils with higher pH, but P was low overall in the forest soil. Results from this study show that low pH-values can hamper the establishment of poplar. The availability of Ca, P and Al is also of importance, since they could counteract or increase the adverse effects of low pH-levels.

Replanting at appropriate times after harvesting a coniferous forest stand can help efforts to suppress seedling mortality caused by the pine weevil Hylobius abietis, but optimal times are uncertain. We hypothesized that planting in June rather than May in the third season after harvest would reduce feeding damage by the pine weevil and increase seedling survival rates in central Sweden, where new-generation weevils mainly fly away from their development sites in May/early June. An experimental test of the hypothesis in eight clear-cuts confirmed that planting in June instead of May reduced proportions of seedlings attacked by pine weevil, bark removal from seedlings’ stems, and proportions of seedlings killed by feeding damage. These differences between seedlings planted in May and June declined to some extent with time but still remained significant after two growing seasons. The total seedling mortality after two seasons did, however, not differ significantly between seedlings planted in May an...

Feeding by pine weevil (Hylobius abietis L.) causes severe damage to newly planted conifer seedlings in most parts of Scandinavia. We investigated the effect of planting time and insecticide treatment on pine weevil damage and seedling growth. The main objective was to study if planting in early autumn on fresh clear-cuts would promote seedling establishment and reduce the amount of damage caused by pine weevil the following season. The experiment was conducted in southern Sweden and in south-eastern Norway with an identical experimental design at three sites in each country. On each site, Norway spruce seedlings with or without insecticide treatment were planted at four different planting times: August, September, November and May the following year. In Sweden, the proportion of untreated seedlings that were killed by pine weevils was reduced when seedlings were planted at the earliest time (August/September) compared to late planting in November, or May the following year. This pattern was not f...

Establishing mixed stands by stimulating natural in combination with planting could potentially ensure adequate stocking and meet shifting demands for forest products. Two long-term experiments were separately established in former Norway spruce (Picea abies L. Karst) stands in southern Sweden to be able to evaluate mixed forest establishment and management. The treatment plots were treated with different intensity of soil scarification (disc trenching, soil inversion and control) to test effects of soil disturbance on regeneration success. Five years later, both experiments were used for a first evaluation, where seedlings of all naturally regenerated tree species were counted together with estimates of the cover and height of other vegetation. This was made in sample plots in symmetric grids. Testing the effects of scarification and distance to seed source on natural regeneration of silver birch (Betula pendula Roth.) and downy birch (B. pubescens Ehrh.) showed that both scarification type and degree of soil disturbance significantly affected seedling counts but only if seed sources were close. In conclusion, conventional management practices for regenerating coniferous forest may be suitable for establishing mixed forest stands with combinations of planted and naturally regenerated seedlings.

Hybrid aspen ( L. × Michx.) is a deciduous tree species suitable for producing large amounts of renewable biomass during short rotations. Its potential under North European conditions could be largely extended if not only agricultural land but also forest land was used for cultivation. Unfortunately, the knowledge of appropriate forest site conditions and effects of site preparation methods on hybrid aspen establishment is limited. In this paper, two studies that explore these questions are presented. In the first study, the sensitivity to acid soils was tested under greenhouse conditions in two type of soils: a) peat soil limed to certain pH levels (3.4–5.7) and b) collected forest soils where pH varied from 3.9 to 5.3. The lowest pH level resulted in reduced growth, elsewhere no significant differences were found. The second study was applied in the field and investigated the effect of four site preparation methods on survival and growth. The methods were: 1) control with no site preparation, 2) patch scarification, 3) mounding and 4) soil inversion. While no differences were found for survival, mounding was generally the method with the highest growth and patch scarification was least successful. The result was probably an effect of good soil aeration and less competition from vegetation after mounding. The field study also revealed clonal differences in growth performance, which stresses the importance of clone selection prior to planting. The results of these studies indicate that hybrid aspen is less sensitive to variation in pH and site preparation methods compared with other poplar species, as have been found in similar studies.Populus tremulaP. tremuloides

Forest management in Sweden can be characterized by even-aged silviculture heavily relying on three established harvest regimes: clearcutting, the seed-tree method, and the shelterwood system. Less intense, small-scale retention harvest systems such as single tree and group selection harvest are rarely used. In addition, natural regeneration dynamics without enrichment planting have barely been studied. Consequently, this study examined natural regeneration establishment in a multi-layered Pinus sylvestris-Picea abies forest stand in southwest Sweden after target diameter harvesting and soil scarification. The creation of forest canopy gaps had a positive effect on total seedling density five years after harvest, mainly due to a significantly higher number of Betula pendula individuals. Seedling density of more desirable tree species suitable for continuous cover forestry such as Fagus sylvatica, Quercus petraea and Picea abies also increased substantially in gaps when compared to pre-harvest conditions or the unharvested plots. In contrast, soil scarification did not increase the number of seedlings of desired tree species due to a significant decrease in Picea abies abundance. Soil moisture and gap size significantly improved Betula pendula seedling establishment while a larger number of Quercus petraea seedlings were observed in Vaccinium myrtillus patches. We conclude that canopy gaps are beneficial under the encountered stand conditions to initiate forest regeneration, and that soil scarification without the timely occurrence of a mast year of desired tree species is not effective in the type of forest studied.

International audience; AbstractKey messageThe success of poplar plantations on forest land was affected by soil preparation, plant type, site, and clone. Mounding in combination with large plant types (rooted plants or long cuttings) of site-adapted clones achieved the highest survival and growth.ContextPoplars (Populus species and hybrids) are fast-growing trees used to make various products. In north European countries, they are mainly grown on agricultural land, but interest in planting poplars on forest land has increased.AimsPlant damage and mortality problems occur on forest land, probably due to soil conditions and competing vegetation. It is therefore of interest to investigate whether combinations of soil preparation methods and plant materials can improve establishment.MethodsAt three sites in southern Sweden, the effects of four soil preparation treatments (no soil preparation, patch scarification, mounding, soil inversion) in combination with three plant types (short cuttings, long cuttings, rooted plants) were studied.ResultsSurvival and growth were significantly influenced by site, soil preparation method, plant type, and their interactions. Mounding resulted in the best overall performance on all sites. Interactions between site and plant type revealed differences in growth dependent on site conditions, but rooted plants and long cuttings were in general most successful. Patch scarification and short cuttings were associated with lower survival and growth.ConclusionSoil preparation is needed to support survival and early growth, but the combination of method and plant type must be adapted to site conditions. The choice of clones should also be considered.

The pine weevil L. is an economically important pest insect that kills high proportions of conifer seedlings in reforestation areas. It is present in conifer forests all over Europe but weevil abundance and risk for damage varies considerably between areas. This study aimed to obtain a useful model for predicting damage risks by analyzing survey data from 292 regular forest plantations in northern Sweden. A model of pine weevil attack was constructed using various site characteristics, including both climatic factors and factors related to forest management activities. The optimal model was rather imprecise but showed that the risk of pine weevil attack can be predicted approximatively with three principal variables: 1) the proportion of seedlings expected to be planted in mineral soil rather than soil covered with duff and debris, 2) age of clear-cut at the time of planting, and 3) calculated temperature sum at the location. The model was constructed using long-run average temperature sums for epoch 2010, and so effects of climate change can be inferred from the model by adjustment to future epochs. Increased damage risks with a warmer climate are strongly indicated by the model. Effects of a warmer climate on the geographical distribution and abundance of the pine weevil are also discussed. The new tool to better estimate the risk of damage should provide a basis for foresters in their choice of countermeasures against pine weevil damage in northern Europe.Hylobius abietis

A composite lithium battery electrode of LiMn2O4 in combination with a gel electrolyte (1 M LiBF4/24 wt% PMMA/1:1 EC:DEC) has been investigated by galvanostatic cycling experiments and electrochemi ...

A comparative study of the impedance response measured with composite electrodes and thin film electrodes of LiMn 2 O 4 was conducted. The electrodes were prepared on different current collectors (i.e. aluminium, carbonised aluminium and gold) and the experiments were run at various state-of-discharge (SOD) and liquid electrolyte compositions. The impedance response was shown to be strongly dependent on the current collector used. It was demonstrated that the high-to-medium frequency semicircle can be attributed to the contact resistance between the current collector and the active electrode material and that the medium-to-low frequency semicircle can be ascribed to the active electrode material. For the analysis, a mathematical model based on a resistance between the current collector and the active electrode material, interfacial-charge transfer coupled to the double-layer charging and solid-phase diffusion was developed. Potential distribution due to porous electrode effects was also considered. Fitting the model to experimental data enabled reasonable values of the exchange-current density, the double-layer capacitance and the solid-phase diffusion coefficient. However, the very low fitted value of the effective conductivity in the liquid phase indicates that this model does not give a satisfying description of the intercalation process of LiMn 2 O 4 .

Thin films, single particles and a composite electrode of the cathode material LiMn 2 O 4 in the lithium battery system were investigated by linear sweep voltammetry (LSV) in 1 M LiClO 4 +PC:EC. The experimental data were compared to and analysed by mathematical models described in Part I of this work. Analysis of the measured peak potential, E p , showed clearly that the larger the characteristic length, the larger is the potential peak shift, at a given sweep rate. From the observations of the measured peak current behaviour, I p , it seems that the composite electrode and the single particles are semi-infinite diffusion limited at all sweep rates applied. For the thin films, when increasing the sweep rate, a transition from finite to semi-infinite mass transfer limitation is indicated. A model based on solid-phase diffusion, interfacial charge transfer and an external IR -drop could fairly well be fitted to the experimental data measured on a single electrode system at a given sweep rate. It was found that the determined parameter values, i.e. solid-phase diffusion coefficient and the IR -drop, vary greatly with sweep rate and characteristic length. These results indicate that the physical description used is an oversimplification for describing the reaction mechanism in LiMn 2 O 4 .

An electrochemical impedance spectroscopy method utilizing the signals from reference electrodes positioned in front of and behind a porous electrode is investigated. The basis for the method is illustrated theoretically, and limiting values under different assumptions are presented. The method was applied to a porous metal hydride and a LiMn 2 O 4 battery electrode. It was concluded that the method facilitates the separation of local impedance effects from the effects of the potential distribution in the porous electrode. Consequently, a more accurate determination of local kinetic parameters and the effective conductivity in the pore electrolyte could be obtained.