Scandinavian Journal of Forest Research

Coastal spruce forests of central Norway harbour a unique assemblage of epiphytic lichens and are given high priority with respect to conservation of biodiversity. To assess the historical impact of logging during the last 100-150 yrs, 31 remnant stands were studied by means of tree-ring analysis of 2199 trees and the decay stage of 1605 stumps. No stands had been clear-cut, but all had been selectively logged at least twice during the last 150 yrs. Total harvested timber volume ranged from 65 to 409 m3ha-1 (31-124% of present-day standing volume) and the selective logging kept standing volume low (40-200 m3ha-1) during 1890-1930. Present-day stand characteristics were strongly correlated with site productivity and topographic position within the ravine valleys. Low amounts of dead wood at sites with high historical logging activity was the only consistent relationship found after covariance of site productivity, topographic position and deciduous trees were taken into account. The results indicate that old-growth stand characteristics, such as reversed J-shaped age distributions and dead wood in advanced decay classes, can be obtained 100-150 yrs after intensive selective logging.

The pine weevil, Hylobius abietis (L.), is a major pest in conifer reforestation areas in the Palaearctic region. Size and chemistry of the seedlings may explain the damage rates in plantations. The performance of 10-week containerized seedlings (mini-seedlings) was compared with 1-year-old conventional seedlings of Norway spruce, Picea abies (L.), in a field experiment in central Sweden. After 2 years the weevil damage was lower for the mini-seedlings than for the conventional seedlings (3.5 vs 55%). After 3 years, the overall survival was 82 and 75%, respectively. Weevil damage was the main cause of mortality for conventional seedlings, whereas mini-seedlings mainly died from drought. Volatiles of the two seedling types were compared by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Unwounded mini-seedlings and conventional seedlings differed in their compositions of monoterpenes and sesquiterpenes. Mini-seedlings mainly emitted limonene, known to be repellent to the pine weevil. When wounded, green leaf volatiles were released by mini-seedlings while the pine weevil attractant α-pinene was released by conventional seedlings. Volatiles may partly explain the mini-seedlings' resistance against weevil attack. Further studies are needed to clarify how long this mini-seedling effect remains.

Knowledge on the pattern of variation in growth rhythm among Baltic Picea abies populations is limited. Growth rhythm of 108 Picea abies provenances from the Baltic states, north-eastern Poland, western Russia, north-western Belarus, Sweden and southern Finland was studied for three growth periods in two nursery trials located in central Sweden and in central Lithuania. Damage by natural frost desiccation was assessed at an age of two years in the Swedish trial. Variation among the Baltic provenances in juvenile growth rhythm traits was essentially clinal over latitude and longitude. According to a multiple regression function, a change in 1° of latitude corresponded to 2.4° degree change in longitude. When moving from the north-eastern part of Poland towards north-east, the seedlings became shorter and more tolerant to frost desiccation with earlier budburst and budset. Photoperiod and temperature climate were identified as the main determinants for the clinal variation among the Baltic populations of Picea abies in growth rhythm traits over the ecological gradients from south to north and from coastalto inland sites.

The growth rates of Heterobasidion annosum in Norway spruce were investigated in southern Sweden. In one study, stump and tree roots in stands established on previous forest or arable land were inoculated with H. annosum-infested sawdust. After 1-3 yrs, the linear extent of colonization by the fungus was measured, based on detection of its conidiophores on incubated samples. The average growth rate was 25 cm yr-1 in stump roots and 9 cm yr-1 in tree roots, neither of which differed significantly between forest and arable land. The felling of a decayed tree could enhance the spread of H. annosum within root systems. In the second study, the height of discoloration and extent of colonization by H. annosum, measured as above, were assessed in naturally infected trees. On average, discoloration moved through the roots and stem at a rate of 36 cm yr-1. Heterobasidion annosum was found 60 cm in advance of the discoloration, corresponding to a growth rate of 52 cm yr-1.

Mortality, injury and height growth of planted Picea abies (L.) Karst. were examined over a 6 yr period in eight stands at middle altitudes (430-620 m a.s.l.) in south-east Norway. There were four residual stand density treatments (shelterwoods of high, medium and low density, 25×25 m patch-cut) combined with three scarification treatments (unscarified, patch scarification, inverting) in a split-plot design. Mortality was very low during the experimental period, and did not differ significantly between the residual stand density treatments (mean=11.1%). Both survival and plant height after 6 yrs were improved by inverting, while patch scarification was intermediate but not significantly different from the unscarified alternative. The patch-cutting resulted in the tallest plants, while only minor differences in height growth were found between the shelterwood treatments. The frequency of injured plants after 6 yrs was not significantly affected by the treatments (mean=10.6%). The improved plant establishment at inverting is in agreement with previous studies on clear-cuts.

Hylobius abietis (L.) (Coleoptera:Curculionidae) is the major insect pest of forest regeneration in Europe, where adult weevils kill conifer seedlings by feeding on the bark. This study demonstrates that pine weevils also feed extensively in the crowns of mature coniferous trees. Crown feeding primarily took place during a limited period immediately after the migration to new breeding sites (roots of freshly cut coniferous trees). The weevils reached the crowns mainly by flight and tended to concentrate on trees in freshly cut-over areas. The proportion of sexually mature females successively increased during the crown-feeding period, indicating that they require a certain period of maturation feeding. The pine weevils fed on twigs of 3–20 mm thickness, and they consumed about 0.2–0.3% (200 cm2) of the total bark surface in the crowns of mature Scots pine trees. Calculations suggested that the amount of food consumed in the trees surrounding a fresh clear-cutting should have met the nutrient requirements of the weevil population in the area during the maturation feeding period. In the crowns of shelterwood trees, about 50 cm2 of the bark was consumed per tree (0.63 m2 ha-1). This level of consumption is not believed to be high enough to relieve the feeding pressure on seedlings and thereby explain the low level of damage usually found under shelterwoods.

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 ground vegetation, scarification (mound) and planting late in the season. In addition, the effects of slash removal and seedling type were studied. The pine weevil was, by far, the dominant damaging agent. Planting without insecticide or soil treatment on fresh, one- or two-year-old clear-cuttings resulted in a mean level of weevil-caused mortality exceeding 60%. The results indicate that the risk of serious damage by pine weevils remains high until the clear-cuttings reach four or five years of age. Killing the vegetation with herbicide had no effect on pine weevil damage. Slash removal decreased damage on older clear-cuttings, but the effect was small. Scarification (mounding) strongly reduced damage. On fresh clear-cuttings the mean mortality caused by pine weevils in mounded plots was 13%, whereas it was 77% in the controls. The mounding effect varied between sites and clear-cuttings of different ages. Late planting (10 June instead of 1 May) reduced damage on two- and three-year-old clear-cuttings. Three-year-old, bare-rooted seedlings were not damaged as seriously as two-year-old, containerized ones, but the effect was probably due to the larger size of the bare-rooted seedlings. Non-lethal injury resulted in reduced seedling growth. Damage by pine weevils varied between years and within growing seasons. However, on fresh, one- and two-year-old clear-cuttings, damage was severe enough to cause high mortality during all studied years.

The main objective of this study was to identify quantitative trait loci (QTLs) involved in the genetic control of growth rhythm and autumn cold acclimation in Pinus sylvestris L. Eighteen full-sib families of P. sylvestris with parental origins between latitudes 62 and 67° N in Sweden were assessed for autumn cold acclimation (frost injury measured from artificial freeze testing) and growth rhythm during the first two growing seasons. One family north×south with 108 individuals was used for the construction of one linkage map for the male and one for the female parent using 286 markers from random amplification of polymorphic DNA. Marker trait associations (QTLs) for shoot elongation, growth cessation and cold acclimation were found on both maps. Some QTLs were verified in two additional north×south families. Proportions of the additive genetic variance explained by the markers (R2G) indicated that genetic factors of large effect were involved in all investigated traits. Single or multiple markers accounted for between 16 and 47% of the additive variance in annual shoot elongation, between 42 and 79% of the additive variance in growth termination, and between 7 and 31% of the additive variation in autumn cold acclimation. The study confirms that there are major QTL regions on different linkage groups controlling a large part of the variation for growth rhythm and autumn cold acclimation in P. sylvestris.

Accumulation of carbon (C) in biomass and soil, and using forest residues for bioenergy are examples of forestry's contribution to reducing the enhanced concentration of greenhouse gases in the atmosphere. The aim of this report was to study the effect of rotation length on carbon accumulation in biomass and soil, and on the amount of forest residues that could substitute fossil fuel during 2000-2100. Two models, based on inventory data from the Swedish National Forest Inventory, were used to simulate the effects of a changed rotation length in the region of Dalarna (1.8×106 ha), in central Sweden. During the studied period, the accumulation of carbon in biomass was 32 kg C ha-1 yr-1 larger for the prolonged rotation period and 105 kg C ha-1 yr-1 smaller for the shortened rotation period compared with the base scenario. The build-up of carbon in forest soil was 23 kg C ha-1 yr-1 larger for the prolonged rotation than for the base scenario, whereas the shortened rotation was 24 kg C ha-1 yr-1 smaller than the base scenario. The potential to substitute fossil fuel was 37 kg C ha-1 yr-1 larger for the shortened rotation and 17 kg C ha-1 yr-1 smaller for the prolonged rotation compared with the base scenario. The annual accumulation of carbon in biomass decreased in all scenarios, which resulted in a prolonged rotation scenario possibly being a poor long-term solution (>100 yrs). The amount of forest residues that could substitute fossil fuel increased in all scenarios during the studied period.

This research reports the major results from an evaluation of the first Nordic operational stand-based forest inventory using airborne laser scanner data. Laser data from a forest area of 250 km 2 were used to predict six biophysical stand variables used in forest planning. The predictions were based on regression equations estimated from 250 m 2 field training plots distributed systematically throughout the forest area. Test plots with an approximate size of 0.1-0.4 ha were used for validation. The testing revealed standard deviations between ground-truth values and predicted values of 0.36-1.37 m (1.9-7.6%) for mean height, 0.70-1.55 m (3.0-7.6%) for dominant height, 2.38-4.88 m 2 ha -1 (7.8-14.2%) for basal area and 13.9-45.9 m 3 ha -1 (6.5-13.4%) for stand volume. No serious bias was detected.

Analysing sustainable forestry at a national level involves many stakeholder groups and multiple resources; thus, analyses tend to be complicated. To evaluate the consequences of different policy options, scenario analyses often are carried out to assess effects in terms of what goods and services can be obtained from forests. This article concerns the provision of input data to such studies. Owing to the complexity of the analyses and the rapid development in the area of forest inventory methodology it is not straightforward to decide how input data should be acquired. This article provides a framework for how analyses of this type can be addressed as well as a case example to illustrate how different data acquisition methods may be evaluated. The framework comprises two steps: the first is to identify the demand of data connected to the resources included in the analysis; the second step is characterizing the quality of inventory data provided by the data acquisition strategy. As an example, three data acquisition strategies were evaluated; none of them was found to be optimal from all points of views and thus the study concludes with a presentation of an integrated method for data acquisition that is based on data from sampled landscape patches.

Information about the state of the forest is of vital importance in forest management planning. To enable high-precision modelling, many forest planning systems demand input data at the single-tree level. The conventional strategy for collecting such data is a plot-wise field inventory. This is expensive and, thus, cost-efficient alternatives are of interest. During recent years, the focus has been on remote sensing techniques. The k nearest neighbour (kNN) estimation method is a way to assign plot-wise data to all stands in a forest area, using remotely sensed data in connection with a sparse sample of field reference plots. Plot-wise aerial photograph interpretations combined with information from a stand register were used in this study. Nearness to a reference plot was decided upon using a regression transform distance. Standing stem volume was estimated with a relative root mean square error (RMSE) equal to 20% at the stand level, while age could be estimated with a RMSE equal to 15%. A cost-efficient data-capturing strategy could be to assign plot data with the presented kNN method to some types of forest, while using traditional field inventories in other, more valuable, stands.

Remote sensing techniques have proven successful for producing stem maps of forests in leaf-on condition from high-resolution imagery. This paper demonstrates how a mathematical model for the surface of a stem can be used to estimate the breast-height diameter of individual trees from aerial photographs to give information on basal area. The diameters are estimated by likelihood estimation from images of a forest in leaf-off condition where the stems and their shadows are visible. Applied to a homogeneous and monospecific oak (Quercus robur L.) stand under standard silvicultural treatment in Denmark, the estimation was successful for 56 out of 60 trees. The root mean squared error on the diameter was 4.2 and 3.2 cm using three and five images, respectively. The key conclusion is that it is feasible to infer fairly accurate information about the diameters and three-dimensional positions of stems from aerial photographs.

The changes in land - use, e.g. afforestation of former agricultural land, or forest management practices, will have an important impact on landscape. Efficient and inexpensive tools are therefore needed in planning for the visualization of future landscape changes. Computer graphics and image - capture techniques can be used to illustrate the present and future states of the sites for the decision - makers. This study examines differences in viewer response to 28 mm panoramic photographs representing 16 rural landscapes and to computer graphic drawings representing the same landscapes. The scenic beauty of the landscapes was assessed first from photographs produced from four original pictures by image - capture technology, with the open agricultural landscape becoming gradually afforested in three stages. The evaluations were then made from computer line graphics illustrations. Scenic beauty was evaluated by using pairwise comparison techniques. The presentation format had little effect on the ratings of the landscapes. The results indicate that the illustration method based on computer line graphics can be recommended for assessing the scenic impact of proposed management actions in distant sceneries.

Diameter and basal area distributions are used in many forest management planning packages for predicting stand volume and growth. The distribution parameters and the 24 and 93 percentiles for parameter recovery of a two-parameter Weibull were derived for empirical diameter and basal area distributions of 54 plots of 3740 m 2 each. Regression analysis was used to relate the distribution parameters and percentiles to various canopy height and canopy density metrics derived from airborne laser scanner data over young and mature coniferous forest. On average, the distance between transmitted laser pulses was 1.0 m on the ground. Aerial photo-interpretation was used to divide the plots into three strata according to age class and site quality. The stratum-specific regressions explained 20-93% of the variability in the observed percentiles. Total plot volume predicted from the estimated distributions was used to assess the accuracy of the regressions. Cross-validation of the regressions revealed a bias of -4.8 to 2.7% between predicted and ground-truth values of plot volume when the predicted frequencies of the diameter and basal area distributions were scaled to ground-truth stem number ( N ) and basal area ( G ), respectively. The standard deviations (SD) of the differences between predicted and ground-truth values of plot volume were 5.6-29.1%. However, when the scaling variables ( N and G ) were predicted from the laser data, the bias of plot volume determined by cross-validation was -4.7 to 6.6% and the SD was 11.4-24.2%.

An extensive literature is available on browsing preference for certain tree species. However, useful predictive tools for estimating the impact of deer on forests production and biodiversity can still be improved. A step in that direction is not only to rank preference among tree species but also to quantify the relative risk of being browsed. The foraging selectivity of moose was evaluated using three different statistical methods developed to study habitat utilization. The general pattern for the three methods was consistent. From the results, groups of forage species were clustered and a quantitative index of selectivity was calculated for the groups. The selectivity index showed that rowan (Sorbus aucuparia), willow (Salix ssp.) and aspen (Populus tremula) had a 14 times higher probability of being browsed than a group consisting of Scots pine (Pinus sylvestris) and downy birch (Betula pubescens), while juniper (Juniperus communis) and silver birch (Betula pendula) had a 3.5 times higher probability than Scots pine and downy birch. Since the most preferred species were the least abundant, one should be cautious about the generality of the index between areas, as it may indicate that preference depends on plant species composition. The method used can easily be applied in forest management. Information on quantitative selectivity indices may improve the possibility of managing moose in accordance with acceptable browsing damage.

No comparisons for Non-Industrial Private Forest (NIPF) owners of the returns on timberland and other investment alternatives, or of the risks in different investments, have been made in Swedish forest economics research. Modern portfolio theory in forest economics has been used to a very small extent in all of Europe, with the exception of Finland. The underlying idea in this study was to apply "the mean-variance framework" in Swedish forest holdings and make comparisons with some other investment alternatives. The results showed that forest holdings had a medium-high return and a high risk. Shares showed high returns and a relatively high risk. Bank assets showed low returns and a low risk. The lowest returns were seen for agricultural holdings. There were negative correlations for forest holdings with several other assets, which means that forest as one investment in a portfolio can be defended when the risks are spread out over time. The result indicates that it would be of interest for NIPF owners to reduce their investments in timberland and increase their share holdings. However, the portfolio mixture depends on the risk preferences of the owners.

Stem bases of 210 Fraxinus excelsior trees of three different health categories were sampled by the means of an increment borer in declining ash stands in northern Lithuania. From this number, 15 sound-looking, 132 declining and 63 dead trees from three discrete plots yielded 352 isolates, representing 75 fungal species. In addition, mycelial fans and rhizomorphs typical of Armillaria spp. from 205 and 20 trees, respectively, were sampled and subjected to fungal isolations. Species richness was similar in trees from each health category, but community structures differed, indicating that species composition of wood-inhabiting fungi in stems changes along with the changes in tree health condition. Armillaria cepistipes was the most common species (86 isolates from 210 wood samples, or 41.0%), isolated more frequently and consistently than any other potential tree pathogen. It also showed abundant occurrence on a majority of trees in the form of mycelial fans and rhizomorphs, from which 64 and 14 isolates of the fungus were obtained, respectively. The population structure of A. cepistipes revealed the presence of 53–93 genets per hectare, some of which extended up to 30–55m.

A method and algorithm for reconstructing the three-dimensional (3D) surface of stems based on terrestrial laser scanner data from standing trees is presented. Laser scanning delivers a dense cloud of points, and this raw point data are filtered for deriving a digital terrain model and subsequent fitting of a parametric stem model. The stem model is made up of a sequence of successive cylinders that overlap in space; each cylinder is parameterized by its orientation and radius. The model is estimated iteratively from a given starting point and by adding cylinder segments. Successive segments are added whenever criteria on deviation in orientation and radius relative to the previous cylinder and a fit statistic to the point data are met. The method has proven applicable when applied to a European beech tree and a wild cherry tree from dense forest stands. The use of the resulting 3D reconstruction of tree stems in respect to diameter in breast height and height of crown base calculation, as well as taper, sweep and lean assessment of standing trees, is described. Finally, desirable future improvements to the basic algorithm are discussed.

Methodology to assess the potential for energy wood procurement in Russia is described in this article and applied to the Leningrad region. Wood from thinnings, logging residues, non-industrial roundwood and residues from sawmilling are considered as sources for energy production. Energy wood available in the region, based on the 2004 actual cut, is approximately 4 million m3. Nearly 86% of this is non-industrial roundwood and felling residues, and 14% is by-products from sawmilling. Almost two-thirds of the non-industrial roundwood and felling residues are in cutting areas and one-third is in central processing yards. Deciduous tree species (birch and aspen) dominate in energy wood, representing about 65% of the total amount of felling residues and non-industrial wood. It is possible to intensify utilization of forest resources and thereby also to increase the use of wood in energy production. The total amount could be 54% higher if the allowable cut was fully utilized and 124% higher if thinnings were also utilized completely. There are, however, significant intraregional differences, as the current rate of utilization of forest resources varies in the region.

Prunus avium L. is a fast-growing hardwood tree species that has demonstrated good production on both well-drained forest soils and farm land in southern Sweden. Growth rate and breeding value were tested in 101 open-pollinated single-tree progenies of Swedish origin and five German seed sources. After eight growing seasons and two selective thinnings the mean tree height reached 4.7 m. The mean tree height of the progenies varied between 3.3 and 6.1 m. A total rotation period of 50-60 yrs and a dominant height of 20-22 m can be expected. The results indicated great phenotypic variation within progenies and good possibilities for improving production and stem quality by early selective thinning. In terms of height growth and stem straightness the best Swedish progenies were as good as the tested German seed sources.

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.

On 30-31 August 1997, a thunderstorm accompanied by heavy rain caused flood erosion on the forest-covered slopes of Mt Fulufjäll in central Sweden. Large numbers of mature Norway spruce trees [Picea abies (L.) Karst.] were uprooted and deposited along streams in the area. Attacks by bark- and wood-boring beetles in lying spruces were recorded along three flooded and three unflooded streams in the three years following this flooding event. The bark beetles Ips typographus (L.), Pityogenes chalcographus (L.), Orthotomicus sp. and the cerambycid Monochamus sp. were found to be much more abundant along flooded than unflooded streams. In contrast, the bark beetle Hylurgops glabratus (Zett.) showed the opposite pattern. Mortality among standing trees peaked in the second year following the flooding event. A considerable proportion of this additional tree mortality could be attributed to attacks by I. typographus. In contrast, no trees killed by this species were found along the three unflooded streams.

Altogether 335 species of saproxylic beetles were collected by Malaise, window and emergence traps in a 33 ha forest reserve in southern Norway, during the years 1992 - 1997. Most species are associated with deciduous trees, particularly oak, and the majority depend on decayed wood or fungi. The forest is a mixture of Norway spruce and deciduous trees and is characterized as being very close to a primeval forest. Sixty - two species of the collected beetles are assumed to be threatened or rare in Scandinavia, 52 species are on the Red Data List in Sweden and 43 species are suggested for a similar list in Norway. Fifteen species are on a list of species threatened in the Nordic region. Compared with other thoroughly sampled forest reserves in Fennoscandia, the forest investigated had one of the richest saproxylic beetle communities known to date. The main reasons for this are assumed to be the abundance of dead wood, the diverse tree composition and the fact that the area had been inaccessible for forest harvesting due to the lack of transportation for timber.

This study investigated the occurrence of 25 forest bird species in relation to stand and landscape habitat composition in managed boreal forests in central Sweden. The number of species in 10 km transects was positively correlated to the proportions of forest >40 yrs and Mixed forest >40 yrs, as well as the number of fragments of the latter, while negatively correlated to the proportions of clear-cuts and young forest. Transects with >60% older forest including >6% mixed habitats showed the highest number of bird species and individuals. The positive effect on species numbers of mixed forest was stronger in the study area where deciduous rich habitats were generally less abundant. Bird species richness in points of similar habitat was negatively correlated to the degree of fragmentation of the surrounding older forest. However, in a species-by-species analysis at the transect level no effects of fragmentation were found. The number of bird species at points was positively influenced by the increase from 0 to 5% deciduous trees, while no effect of higher deciduous site proportions showed. The hazel grouse (Bonasa bonasia) appeared as a significant indicator of high bird diversity at the transect (landscape) level, by all methods used. However, the conclusion was reached that forests where the hazel grouse, blue tit (Parus caeruleus), treecreeper (Certia familiaris), jay (Garrulus glandarius) and capercaillie (Tetrao urogallus) are present are most likely to hold the potential for high bird species richness.