Potential production of Norway spruce in Sweden

In this paper, the potential stem wood production for Norway spruce was estimated for different regions in Sweden. This was done by using basic physiological relationships of intercepted radiation versus biomass production and knowledge of how a water deficit reduces the potential production, derived from results of field experiments on nutrient optimisation. To scale these relationships up to regional and national levels, data of incident radiation and humidity during the growing season for all of Sweden were used. The figures for potential and attainable production indicate that the temperate to boreal climate allows considerably higher production than the current production, if availability of water and nutrients is non-limiting. In northern Sweden, the attainable production is ca. 300% higher than the current production and in southern Sweden, the yield can be increased by ca. 100%. In absolute numbers, as a mean for a whole rotation period, it is possible to achieve an annual stem-wood dry mass production of 7–9 Mg ha⁻¹ in southern and central and ca. 5–6 Mg in northern Sweden. This increased production would mean that rotation periods can be shorter than they are now by 20–30 years in southern Sweden and by ca. 50–60 years in northern Sweden.     

Radial distributions of Pb in stems of young Norway spruce trees grown in Pb-contaminated soil

Concentrations of Pb in individual stem xylem rings of 5-year-old Norway spruce trees (Picea abies (L.) Karst.) were determined after one growing season in soil containing a low, medium or high concentration of Pb. In trees in the control and low-Pb soil treatments, Pb concentrations increased from the outer annual rings toward the stem center, whereas in trees grown in the soil treatment containing a medium Pb concentration, all of the four tree rings analyzed contained similar concentrations of Pb. Although trees grown in the high-Pb soil treatment had higher concentrations of Pb in the outer annual rings than both control trees and trees in the low-Pb soil treatment, the highest concentrations of Pb were never observed in the outermost rings, which were formed during the period of exposure to increased soil Pb. We conclude that radial distribution patterns of Pb in Norway spruce stems do not directly reflect changes in soil Pb concentration but depend on several internal, physiological factors and, therefore, do not provide reliable information about past variations in Pb contamination of soil.     

Sporendocladia bactrospora associated with wounds on native broadleaved trees in Norway and Sweden

A survey to identify ophiostomatoid fungi that infect wounds on native Norwegian and Swedish broadleaved trees was undertaken during summer 2004. A fungus resembling a species of Sporendocladia was commonly isolated from the exposed cambium and inner bark of wounds. Morphological examination and comparisons of DNA sequence data for the ITS and 5.8S regions of the rRNA gene region led to its identification as Sporendocladia bactrospora. Pathogenicity trials on young Populus tremula and Betula pubescens trees showed that S. bactrospora is capable of causing lesions on these trees. There have been few previous reports of S. bactrospora, and in most cases, these have been as saprophytes on wood. In contrast, results of this study show that it is a common inhabitant of freshly made wounds on native broadleaved trees in Scandinavia, and it appears to contribute to staining of wood.     

Autumn frost hardiness in Norway spruce plus tree progeny and trees of the local and transferred provenances in central Sweden

Reforestation with provenances from locations remote from the planting site (transferred provenances) or the progeny of trees of local provenances selected for superior form and vigor (plus trees) offer alternative means to increase yield over that obtained by the use of seed from unselected trees of the local provenance. Under Swedish conditions, Norway spruce (Picea abies (L.) Karst.) of certain transferred provenances generally has an advantage in productivity relative to the local provenance comparable to that of progeny of plus trees. The aim of this study was to explore the extent to which productivity gains achieved by provenance transfer or the use of plus tree progeny are associated with reductions in autumn frost hardiness, relative to that of trees of the local provenance. In a field trial with 19-year-old trees in central Sweden, bud hardiness was tested on four occasions during the autumn of 2002. Trees of the local provenance were compared with trees of a south Swedish provenance originating 3 degrees of latitude to the south, a Belarusian provenance and the progeny of plus trees of local origin. The Belarusian provenance was the least hardy and the local provenance the most hardy, with plus tree progeny and the south Swedish provenance being intermediate in hardiness. Both the Belarusian provenance and the plus tree progeny were significantly taller than trees of the other populations. Within provenances, tree height was negatively correlated with autumn frost hardiness. Among the plus tree progeny, however, no such correlation between tree height and autumn frost hardiness was found. It is concluded that although the gain in productivity achieved by provenance transfer from Belarus was comparable to that achieved by using the progeny of plus trees of the local provenance, the use of trees of the Belarus provenance involved an increased risk of autumn frost damage because of later hardening.     

Effects of repeated fertilization in young Norway spruce forests

Several studies have shown the positive effect of nitrogen fertilization on conifer growth. In young Norway spruce (Picea abies) stands, an additional effect of including a mixture of other nutrients has often, but not always, been found. We studied effects of repeated fertilization in 28 stands with young Norway spruce in central Norway. The treatments consisted of plots without nutrient addition (Control), fertilization with 150?kg?N?ha^?1 (150?N), and fertilization with 150?kg?N plus addition of P, K, Mg, B, Mn and Cu (150?N?+?mix), repeated three times with approximately eight years interval. There was a clear positive effect on volume increment of the 150?N and 150?N?+?mix treatments compared to Control, and the effect was significantly higher for 150?N?+?mix than for 150?N. Fertilization had a stronger effect in the first fertilization period than in the second, while the third period was intermediate. The effect of 150?N?+?mix was strongest at plots?>?300?m a.s.l. However, this correlation may be due to geological conditions rather than elevation. Further studies are needed to find out under which edaphic conditions a nutrient mixture will increase growth substantially in young spruce stands.     

Hydraulic and stomatal adjustment of Norway spruce trees to environmental stress

A study of how the water conducting systems of 30-50-year-old Norway spruce (Picea abies (L.) Karst.) trees growing at three sites adjust to shade and waterlogging indicated that water relations characteristics varied with the life histories of the trees. Xylem was more efficient at conducting water and stomata were more sensitive to atmospheric evaporative demand in trees subjected to favorable growth conditions (control trees) than in trees growing in shade or waterlogged conditions. At the same soil water availability, shade-grown trees suffered more severely from water deficit than control trees. Under conditions of high atmospheric vapor pressure deficit, foliage of shade-grown trees exhibited low water potentials, as a result of low hydraulic conductance of the vascular system and inefficient stomatal control. Because of the increased internal resistance to water flow, more negative leaf water potentials (Psi(x)) must be reached to provide an adequate water supply to the foliage. It is concluded that dynamic water stress is one of the main causes of the continuing growth retardation in suppressed Norway spruce trees after their release from the overstory. Trees growing in waterlogged soil (bog-grown trees) were characterized by weak stomatal control, resulting in large water losses from the foliage. Although bog-grown trees exhibited uneconomical water use, they possessed mechanisms (e.g., osmotic adjustment) that allowed leaves to tolerate low Psi(x) while stomata remained open. Under conditions of sufficient soil water availability and moderate atmospheric vapor pressure deficit, soil-to-leaf conductance was highest in bog-grown trees (1.45 +/- 0.06 mmol m(-2) s(-1) MPa(-1)), followed by control and shade-grown trees (1.04 +/- 0.04 and 0.77 +/- 0.05 mmol m(-2) s(-1) MPa(-1), respectively). The lowest soil-to-leaf conductance (0.45 +/- 0.04 mmol m(-2) s(-1) MPa(-1)) was recorded in control trees at high atmospheric evaporative demand, and was probably caused by tracheid cavitation.     

Biomass functions and expansion factors in young Norway spruce (Picea abies [L.] Karst) trees

Roots, stems, branches and needles of 160 Norway spruce trees younger than 10 years were sampled in seven forest stands in central Slovakia in order to establish their biomass functions (BFs) and biomass expansion factors (BEFs). We tested three models for each biomass pool based on the stem base diameter, tree height and the two parameters combined. BEF values decreased for all spruce components with increasing height and diameter, which was most evident in very young trees under 1 m in height. In older trees, the values of BEFs did tend to stabilise at the height of 3–4 m. We subsequently used the BEFs to calculate dry biomass of the stands based on average stem base diameter and tree height. Total stand biomass grew with increasing age of the stands from about 1.0 Mg ha⁻¹ at 1.5 years to 44.3 Mg ha⁻¹ at 9.5 years. The proportion of stem and branch biomass was found to increase with age, while that of needles was fairly constant and the proportion of root biomass did decrease as the stands grew older.     

Fatty acids of ozone-exposed Scots pine and poplar trees and of damaged field-grown Norway spruce trees

In foliage of Pinus sylvestris, Populus euramericana, and Picea abies the fatty acid composition was analyzed. Whereas clonal material of pine and poplar in controlled ozone fumigations did not show any significant differences as compared to controls, such differences were obtained in fieldgrown spruces showing needle loss.     

Effect of wide spacing on increment and branch properties of young Norway spruce

The effects of stand density on increment and branch properties were studied in three spacing experiments of Norway spruce [Picea abies (L.) Karst.]. The stand densities ranged from 350 stems ha⁻¹, regarded as open-grown trees, up to 1,600 stems ha⁻¹, corresponding to the density recommended for forestry practice. Properties of all the branches were measured from the stem apex downwards. The study material included a total of 5,661 branches from 45 trees. Increasing stand density resulted in a decrease in radial increment as well as shorter and narrower crowns, but it had no effect on height increment. The average number of spike knots per tree was 0.87, 0.27, and 0.33 in densities of 350, 700 and 1,600 ha⁻¹, respectively. Additionally, in the widely spaced stands of 350 stems ha⁻¹, the fraction of trees having spike knots was high (over 50%). At a density of 1,600 ha⁻¹, the sample trees had somewhat less branches in a whorl compared with the more widely spaced plots. The most pronounced effect of stand density was the increase in branch diameter with decreasing stand density. At a density of 350 ha⁻¹, the maximum branch diameter of all the sample trees exceeded the diameter limit of quality class B in the European quality requirements for round wood. The results give some indication that trees subjected to severe competition would produce smaller branches per unit of crown projection area. However, the possibilities for reducing branch dimensions relative to stem and crown size through competition appear quite restricted.     

Influence of gaps on some selected tree characteristics of edge trees in Norway spruce plantations

The present study examined branch and stem characteristics of trees growing around gaps in Norway spruce plantations. Trees located at the edge of gaps with a radius of either 5 m or 7 m either unplanted or with supplementary planting were compared to trees in the original closed plantation. The experiment was carried out in two locations in the south of Sweden and the design included four blocks at each location and one replicate of each treatment in each block. The measurements were carried out on standing and felled trees in 2005 at the time of the first thinning. The results indicate a significant effect of gaps and supplementary planting on the diameter of the largest branch, the number of living branches close to breast height, branch basal area, height to the first living branch and taper. The effect of supplementary planting on branch and stem characteristics was greater in large gaps than in small ones. This study indicated that supplementary planting may be useful in affecting stem-form and branch parameters, although other studies have shown that the trees that result from supplementary planting contribute little to total production.     

Occurrence of microorganisms in the wood of Norway spruce trees from polluted sites

Bacteria, yeasts and other fungi were isolated from stem and root wood of Norway spruee trees with disease symptoms and were identified in order to evaluate a possible mierobial involvement in the widespread tree decline in Central Europe.     

Improved varieties perform well in realized genetic gain trials with Norway spruce seed sources in southern Sweden

ABSTRACT

Genetically improved Norway spruce (Picea abies L. Karst) has been extensively used in operational plantations in Sweden. However, there have been few studies that aimed at verifying the realized genetic gain over a longer time span in plots established with one genetical entry. Two experimental series at six sites in southern Sweden, established purely for this purpose, were assessed. Early height growth of 10 Norway spruce seedlots of different genetic levels was compared. There were significant differences in height at the age of 5 and 8 years between improved and unimproved seed sources and the differences between most advanced material from the breeding front, represented by full-sib crossings of selected plus-trees, and unimproved Swedish spruce were 36% and 30% at the age of 5 and 8 years, respectively. At the same ages, the trees originating from the second round of seed-orchards were 25% and 21% higher than unimproved material. There were also about 20% differences between the best and worst tested full-sib families, indicating large possible gain in the new generation. The study confirmed earlier estimates of genetic gain levels of different seed sources in the breeding program for Norway spruce.     

Root preparation technique and storage affect results of seedling quality evaluation in Norway spruce

Evaluation of tree seedling quality is necessary for improving technology for forest nursery production and seedling handling. Nutrient status can be measured to determine seedling quality, but it can be affected by seedling handling techniques. In this study effects of root preparation technique and storage regime on content of macro nutrients (N, P, K, S, Ca, Mg) in fine roots of Norway spruce (Picea abies (L.) Karst.) plants were investigated. The root preparation techniques were: (a) rinse in tap or (b) deionised water, and (c) dry preparation. These techniques were tested on seedlings subjected to four storage regimes: (1) no storage, (2) deep freezing below −20°C, and long-term (3) cold (+1 to +3°C) and (4) frozen (−3 to −4°C) storage. From the results it was concluded that the nutrient status in needles is not sufficient to describe the whole plant nutrient status in stored dormant plants, fine roots should also be included. The results also showed that deep freezing of fine roots before nutrient analyses should be avoided. Losses of K, P, S, and Mg were substantial with this method. Deionised water or dry preparation is preferred since tap water contains substantial amounts of ions that may affect the analyses.     

Pre-commercial thinning,birch admixture and sprout management in planted Norway spruce stands in South Sweden

Early management of the regenerated seedlings shapes the future stand properties. To address these issues, pre-commercial thinning (PCT) and control treatments were applied to planted Norway spruce (Picea abies L. Karst) and naturally regenerated birch (Betula pendula Roth., Betula pubescens Ehrh.) stands in forest experiments in southern Sweden (lat. 56–57?N) containing 1.1–5.5?m tall saplings. The treatments were retention of 1000 or 2000?stems?ha^?1 of Norway spruce, with no birch or birch at 1000?stems?ha^?1. Treatments were replicated with and without annual removal of birch sprouts from stumps. The periodic annual increment (PAI) over five years was calculated for total stand volume and individual trees. The mean PAI of dominant trees was significantly higher both following all PCT treatments than controls, and following low rather than high-density PCT. Birch retention did not affect growth of the dominant trees but PAI was lower in plots with uncontrolled sprouting. The PAI of birch was significantly higher in low-density Norway spruce plots than in control plots and the high-density plots. The treatment response was significant even in stands with initial heights of only 1–2?m.     

Basal area growth models for individual trees of Norway spruce, Scots pine, birch and other broadleaves in Norway

Distance-independent individual tree growth models based on about 30,000 observations from the National Forest Inventory and the Norwegian Forest Research Institute have been developed for the main tree species in Norway. The models predict 5-year basal area increment over bark for trees larger than 5 cm at breast height. Potential input variables were of four types: size of the tree, competition indices, site conditions, and stand variables including species, mixtures and layers. The squared correlation coefficient (R²) varied from 0.26 to 0.55. The accuracy of the models was tested by comparing the individual tree models with Norwegian diameter increment models. The accuracy is similar, but individual tree models forecast diameter distributions directly. The inclusion of species mixture and layer as variables increases the reliability of the models in mixed and in uneven-aged stands.     

A comparative study of above- and below-ground parameters of healthy and declining young Norway spruce trees in a mountain area affected by air pollution

The aim of this study was to characterize possible connections between above- and below-ground parameters and the decline of Norway spruce trees in the Jeseníky Mountains of the Czech Republic – an area affected both by long-term air pollution and subjected to liming. A part of this study was dedicated to soil analysis, which showed considerable changes in the soil environment and highlighted particularly high concentrations of magnesium and calcium, exceeding optimal limits by as much as 8 and 13 times, respectively. Our results suggest that the decline of evaluated trees is primarily connected to root system development, as we found no differences between evaluated above-ground parameters for either healthy or declining trees. Tree decline related directly to low numbers of skeletal roots, root origin and higher maximal angles between skeletal roots. Declining trees had on average five skeletal roots with maximal angles between them of 173^o, indicating poor mechanical stability. Regardless of tree vitality, 93% of all examined root systems were restricted to upper humus horizons with an average rooting depth of 10.2?cm. All evaluated trees showed severe root deformation into tangle, which suggests crucial influence of artificial planting on the architectural development of root systems.     

Infection studies with Heterobasidion annosum on young trees of Picea abies

Infection studies with Heterobasidion annosum were carried out on 15-year-old, cloned spruces between 1971 and 1978. The inoculum was introduced into the sapwood of the test plants at the base of the stem. All inoculations, conducted at different times of the year, were uniformly successful. The pathogen spread through the xylem tissue rapidly during the vegetation period, but from early autumn onwards gradually disappeared over the following two years. After this period, the fungus could no longer be detected.     

Effect of nitrogen on the seasonal course of growth and maintenance respiration in stems of Norway spruce trees

To determine effects of stem nitrogen concentration ([N]) on the seasonal course of respiration, rates of stem respiration of ten control and ten irrigated-fertilized (IL), 30-year-old Norway spruce trees (Picea abies (L.) Karst.), growing in northern Sweden, were measured on seven occasions from June 1993 to April 1994. To explore sources of seasonal variation and mechanisms of fertilization effects on respiration, we separated total respiration into growth and maintenance respiration for both xylem and phloem bark. Stem respiration increased in response to the IL treatment and was positively correlated with growth rate, volume of living cells and stem nitrogen content. However, no significant effect of IL treatment or [N] in the living cells was found for respiration per unit volume of live cells. Total stem respiration during the growing season (June to September) was estimated to be 16.7 and 29.7 mol CO(2) m(-2) for control and IL-treated trees, respectively. Respiration during the growing season accounted for approximately 64% of total annual respiration. Depending on the method, estimated growth respiration varied between 40 and 60% of total respiration during the growing season. Between 75 and 80% of the live cell volume in the stems was in the phloem, and phloem maintenance accounted for about 70% of maintenance respiration. Because most of the living cells were found in the phloem, and the living xylem cells were concentrated in the outer growth rings, we concluded that the best base for expressing rates of stem growth and maintenance respiration in young Norway spruce trees is stem surface area.     

Temporal variation and efficiency of leaf area index in young mountain Norway spruce stand

Temporal variation of leaf area index (LAI) in two young Norway spruce stands with different densities was monitored during eight consecutive growing seasons (1998–2005). We focused on: (1) LAI dynamics and above-ground mass production of both spruce stands and their comparison, (2) leaf area duration (LADU), crop production index (CPI) and leaf area efficiency (LAE) evaluation, and (3) thinning impact on the above-mentioned parameters. Also, we tried to deduce the most effective LAI value for the Norway spruce forest investigated. The LAI values of both spruce stands showed a typical seasonal course. To describe the LAI dynamics of the stand, we recommend taking LAI measurements within short time intervals at the time of budding and needle expansion growth (i.e., in early spring) and close to the LAI peak, when the twig growth has been completed. The reason was that after reaching the seasonal maximum, no significant differences between subsequently obtained values were found in the following 2 months. Therefore, we recommend this period for the estimation of seasonally representative LAI values, enabling the comparison of various spruce stands. The maximum hemi-surface LAI value reached 12.4. Based on our results, the most effective LAI values for maximum above-ground biomass production were within the range of 10–11. We found an LAI over these values to be less effective for additional production of above-ground biomass. In forest practice, thinning intensity is mostly described by percentage of stocking reduction. We want to show that not only thinning intensity, but also the type of thinning is important information. The type of thinning significantly affected the stand above-ground biomass increment, canopy openness, stand LAI and LAI efficiency. The stimulating effect of high-type thinning was observed; the LAE as well as the CPI increased. Low-type thinning had no such effects on LAE increments compared to the high-type thinning with similar intensity.

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