Application of random amplified polymorphic DNA (RAPD) to detect genetic variation in Norway spruce

The RAPD assay is a screening method for genetic variation; in Norway spruce biology research, it may find many applications. We have investigated into its suitability for Norway spruce genetics by optimizing the protocol, testing for stability in clones, especially tissue culture clones, assessing the variation in a seed sample, and checking for correct Mendelian segregation in haploid megagametophytes. The RAPD assay produced numerous genetic markers quickly. The data obtained gave insight into the genetic make-up of clones and seed.

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Zusammenfassung Die RAPD Methode, ein Schnelltest für die genetische Variation, wurde für die europäische Fichte getestet, wo viele Aspekte der Biologie der Baumart damit untersucht werden könnten. Das Protokoll wurde optimiert, und genetische Stabilität in Klonen, besonders aus Gewebekultur, die genetische Variation in einer Samenprobe und die Mendel-konforme Aufspaltung in haploiden Megagametophyten wurde untersucht. Zahlreiche genetische Marker konnten gefunden werden, wodurch ein Einblick in die genetische Zusammensetzung des untersuchten Materials gegeben war.

     

Interactions between soil scarification and Norway spruce seedling types

Interactions between scarification treatments and seedling types of Norway spruce were examined at two different locations in southern Sweden. The scarification treatments were not scarified control, mounding and soil inversion and the seedling types were a 10 week-old containerized seedling (mini seedling), a 2 year-old containerized seedling and a 2 year-old hybrid seedling, grown as a containerized seedling the first year and as a bare-root seedling the second year. Site preparation intensity had a greater effect on the mini seedlings. The results indicated that mini seedlings established faster in the soil inversion treatment compared to the larger seedling types. At the same seedling age, the mini seedlings had faster or similar growth rate as the containerized and the hybrid seedlings regardless of scarification treatment. Although mini seedlings grew as well as or even better than larger seedlings if they were successfully established, they were more sensitive to their planting environment and proper handling was critical. Problems with frost heaving and competing vegetation have to be taken into consideration when choosing site preparation method and seedling type.     

Thinning intensity effects on carbon and nitrogen stores and fluxes in a Norway spruce (Picea abies (L.) Karst.) stand after 33 years

The present paper deals with C and N storage in soil and vegetation, litter fall and CO₂ efflux from the soil 32–33 years after early thinning in a Norway spruce (Picea abies (L.) Karst.) stand in order to evaluate the effect of thinning regime on C sequestration. At 22 years old, the stand was reduced from 3190 to 2070, 1100 and 820 trees per hectare in four replicates. The N2070 treatment represents the recommended start density in practical forestry, while the other represent a moderate to large reduction in tree number at the present stand age. Aboveground biomass was estimated from single tree measurements of diameter and height based on allometric functions. Litter fall was collected during one and a half years and soil respiration was measured on five occasions during one summer. Ground vegetation was mapped and sampled for biomass, C and N determination. A significant decrease in aboveground tree (including stump-root system) C storage of 27% and 22% due to thinning was found in the N820 and N1100 treatments, respectively, compared to the N2070 treatment. Ground vegetation C storage was little affected by treatment, while litter fall C showed a non-significant decrease in the N820 and N1100 treatments compared to the N2070 treatment. Soil respiration was significantly lower in parts of the summer in the N2070 treatment compared to the N820 treatment. The reason for this is still unexplained since no differences in soil temperature, soil moisture or litter fall chemistry was found between the treatments. No significant treatment effects on humus and mineral soil C storage could be detected. With the present soil variability, the time period of 32 years is probably too short to detect soil C differences due to thinning. The N storage followed the same pattern as for C.     

Reduction of frost heaving of Norway spruce and Scots pine seedlings by planting in mounds or in humus

This study was carried out in northern Sweden to determine the effects of frost heaving on the establishment of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings in relation to planting methods. For this purpose, one year old containerised seedlings were planted on two sites and on two dates: during the spring (early planting) and during the fall (late planting). In each case, two planting depths (normal and deep planting) and four planting sites (in mineral soil in the depressions, in the scalp/trench area, on the top of the mound and in the untreated humus layer) were used. On each site, 50 seedlings were planted for each treatment. Frost heaving was observed and measured during two years. The amount of heaving was highest in the hole and almost insignificant on the top of the mound and in the humus layer. Planting depth influenced the degree of heaving only for Scots pine planted in the hole and was not related to the planting time.     

Pine weevil (Hylobius abietis) damage to cuttings and seedlings of Norway spruce

Damage caused by pine weevil (Hylobius abietus L.) to planted seedlings and cuttings of Norway spruce (Picea abies (L.) Karst.) was studied at five clearcut sites in south-eastern Sweden. The main objective was to compare the two types of stock in terms of attack frequency and mortality due to pine weevil feeding. Cuttings and seedlings with the same initial stem-base diameter (4 mm) were compared. Two sites were harvested and scarified shortly before planting, two were harvested shortly before planting, but were not scarified, and one was harvested 2 years before and scarified the autumn before planting. The total mortality 5 years after planting was highest, greater than 90%, at the new, non-scarified sites, and lowest, 23%, at the old, scarified site. More than 90% of the mortality was caused by pine weevil feeding. Attack frequency and pine weevil induced mortality were significantly higher among seedlings than among cuttings. Mortality due to pine weevil damage was 4–43% higher in seedlings than in cuttings after the fifth year. Of the cuttings and seedlings that were attacked in the first year, a significantly higher frequency of the seedlings were girdled. The higher resistance of cuttings to pine weevil damage may partly explain the more rapid growth of cuttings reported in other studies. However, the causes of their higher resistance need to be further investigated. The thicker bark and needles on the stem base of the cuttings could be important in this respect.     

Decomposition of stump and root systems of Norway spruce in Sweden—A modelling approach

The demand for quantifying the biomass of stumps and roots and the carbon stored therein is related to aspects of biodiversity, site productivity, atmospheric carbon cycling issues, and the demand for bioenergy. This, in turn, creates a need to develop high-quality tools for estimating biomass and carbon-equivalents in the ground. The objective of this study was to develop decomposition functions for quantifying the remaining dry weight of the biomass of individual stumps and their associated roots in Norway spruce (Picea abies (L.) Karst.). The negative exponential model was chosen for this purpose, combined with a chronosequence approach, involving 99 stumps and their roots from three sites in Sweden. The results showed a relative decay rate of 4.6% annually for stump and root systems. Based on this rate, the time required for the loss of 50% (t_0.5) and 95% (t_0.95) of the wood is 15 and 64 years, respectively. Although there are many variables that affect decomposition, residual studies indicated that the remaining biomass could be predicted fairly accurately on the basis of the independent variables stump diameter and time.     

Applicability of non-destructive substitutes for leaf area in different stands of Norway spruce (Picea abies L. Karst.) focusing on traditional forest crown measures

Since individual tree leaf area is an important measure for productivity as well as for site occupancy, it is of high interest in many studies about forest growth. The exact determination of leaf area is nearly impossible. Thus, a common way to get information about leaf area is to use substitutes. These substitutes are often variables which are collected in a destructive way which is not feasible for long term studies. Therefore, this study aimed at testing the applicability of using substitutes for leaf area which could be collected in a non-destructive way, namely crown surface area and crown projection area. In 8 stands of Norway spruce (Picea abies L. Karst.), divided into three age classes and two thinning treatments, a total of 156 trees were felled in order to test the relationship between leaf area and crown surface area and crown projection area, respectively. Individual tree leaf area of the felled sample trees was estimated by 3P-branch sampling with an accuracy of ±10%. Crown projection area and crown surface area were compared with other, more commonly used, but destructive predictors of leaf area, namely sapwood area at different heights on the bole. Our investigations confirmed findings of several studies that sapwood area is the most precise measure for leaf area because of the high correlation between sapwood area and the leaf area. But behind sapwood area at crown base and sapwood area at three tenth of the tree height the predictive ability of crown surface area was ranked third and even better than that of sapwood area at breast height (R² = 0.656 compared with 0.600). Within the stands leaf area is proportional to crown surface area. Using the pooled data of all stands a mixed model approach showed that additionally to crown surface area dominant height and diameter at breast height (dbh) improved the leaf area estimates. Thus, taking dominant height and dbh into account, crown surface area can be recommended for estimating the leaf area of individual trees. The resulting model was in line with many other findings on the leaf area and leaf mass relationships with crown size. From the additional influence of dominant height and dbh in the leaf area model we conclude that the used crown model could be improved by estimating the position of the maximum crown width and the crown width at the base of the crown depending on these two variables.     

Effect of soil chemical properties on growth,foliation and nutrition of Norway spruce stand affected by yellowing in the Bohemian Forest Mts., Czech Republic

In 1998, a fertilizer experiment aiming to investigate the effects of slow-release N, P, K and Mg fertilizer (SILVAMIX Mg NPK^®) on a 60-year-old spruce stand with symptoms of yellowing was established. In this paper, trees were selected to investigate the relation between annual diameter increment, yellowing, foliation, needle and soil chemical properties: ten from the fertilized treatment (F), ten green trees from the control (CG) and ten yellow trees from the control (CY). CG and CY trees were growing in close proximity at a distance of only several meters apart under the same soil conditions. In treatment F, increased annual diameter increment, improved foliation, needle Mg concentration, plant-available Mg and P concentrations in the soil and absence of yellow trees were recorded 7 years after a single application of the fertilizer. During the last 15 years, annual growth increment and foliation of CY trees have continuously decreased while relatively stable values were recorded for CG trees and increased for F trees. In 2006, CG and CY trees differed significantly in Mg concentration in needles, foliation, yellowing and annual diameter increment. Although differences in soil chemical properties between CG and CY treatments were not significant, lower concentrations of plant-available Mg²⁺ and higher concentrations of H⁺ and Al³⁺ were found in soils under CY trees. There was a negative correlation between soil concentration of Mg and yellowing, but this correlation was relatively weak, indicating that there is no simple relation between soil and needle concentrations of Mg. In the investigated locality, the “new type” of yellow tree decline has been a long-term gradual process.     

Predicting regeneration establishment in Norway spruce plantations using a multivariate multilevel model

This study predicts the regeneration establishment on 3-year-old Norway spruce (Picea abies (L.) Karst.) plantations in southern Finland using regeneration survey data. Regeneration establishment was described by seven response variables: number of planted spruces, natural Scots pines (Pinus sylvestris L.), natural spruces, natural seed-origin birches (Betula pubescens Ehrh. and B. pendula Roth.) and other broadleaves (i.e. sprout-origin birches and other broadleaves than birch), as well as height of crop-tree spruce and dominant height of broadleaves. Due to the multivariate (several responses for each plot) and multilevel (plot, stand, municipality, forest centre) structure, regeneration establishment was modelled by fitting a multivariate multilevel model with explanatory variables such as temperature sum, site fertility, soil quality and method of site preparation. In the model, the numbers of tree seedlings were modelled using over-dispersed Poisson distributed equations, and the tree heights were modelled using normally distributed linear equations. The estimated fixed and random parameters of the equations were logical, and there was no serious bias in predicting the regeneration establishment in the independent test data set. This modelling approach can be used to predict the regeneration establishment stochastically by taking into account the large unexplained variation in regeneration models.     

Fibril angle variability in earlywood of Norway spruce using soft rot cavities and polarization confocal microscopy

The main purpose of this study was to investigate the variability of the fibril angle of tracheids in earlywood of Norway spruce (Picea abies L. Karst.). Polarization confocal microscopy was chosen and compared with the method utilizing the orientation of soft rot cavities. There was a significant correlation between the soft rot and polarization confocal microscopy methods, which showed the same trend of high fibril angles in the first part of the earlywood followed by a decrease toward the end of earlywood. This declining trend was less pronounced in annual rings containing compression wood. Moreover, large variations in fibril angle occurred between neighboring tracheids. The investigation also emphasized the differences between X-ray diffraction and microscopic methods, as the large variation seen by the latter methods is not seen by the X-ray diffraction approach because of its large area of measurement. No correlation was found between fiber morphology (i.e., average length, width, density) and the average fibril angle in the investigated annual rings.     

Effect of thawing regime on growth and mortality of frozen-stored Norway spruce container seedlings planted in cold and warm soil

One-year-old frozen-stored Norway spruce (Picea abies (L.) Karst.) container seedlings were planted in a controlled environment providing an air temperature of 22°C and soil temperature of 9±1 or 18±1°C. At planting the root plugs were either frozen or had been thawing for 4 days at 9°C. During a 5-week growing period, in both cold and warm soil the root growth and height growth were less in frozen-planted seedlings than in thawed seedlings. In addition, frozen-planting delayed bud burst and increased mortality. Soil temperature, however, had no effect on bud burst or mortality. Low soil temperature retarded root growth of seedlings thawed before planting but resulted in both retarded root growth and height growth if root plugs were frozen when planted. These results indicate that planting Norway spruce seedlings with frozen root plugs constitutes a considerable risk for successful forest regeneration at soil temperatures normally prevailing in Fennoscandia in spring or early summer especially if the soil is dry at the time of the planting.     

Combined application of computer tomography and light microscopy for analysis of conductive xylem area in coarse roots of European beech and Norway spruce

Axial water transport in trees is mainly determined by the gradient of negative water pressure and the structure of conductive xylem elements (i.e. conduits) connecting the fine roots with the foliage. There is still an essential lack of knowledge concerning the relationship between wood structure and hydraulic properties, especially of coarse roots. To this end, the study aimed (1) to work out a novel approach, based on the combination of computer tomography (CT) and light microscopy (LM), for determining the cumulative cross-sectional lumen area of conduits involved in the water transport of coarse roots in European beech (Fagus sylvatica) and Norway spruce (Picea abies) and (2) to demonstrate its adequacy in quantifying the functional relationship between sapwood anatomy and ascending water mass flow in the xylem. The cross-sectional sapwood area of coarse roots was assessed through CT. The cumulative cross-sectional lumen area of conduits in the sapwood (i.e. the lumen area of conductive conduits) was measured by LM in combination with interactive image analysis. The new approach was developed with coarse roots of both the tree species growing in a 60-year-old mixed forest in Bavaria, Germany. The combination of the two methods unveiled spruce to possess a distinct sapwood/heartwood boundary in small-diameter roots, whereas such roots of beech reflected a gradual transition zone; only large-diameter roots displayed a distinct boundary in beech. Additionally, the cumulative lumen area of conductive conduits was found to be approximately 12% of the total coarse root cross-sectional area in both the tree species. The new approach of measuring the conductive lumen area of coarse-root conduits yielded levels of specific sap flow (i.e. axial conductivity) that substantially differed from those derived from commonly applied methods, which were based on sap flow per unit of total cross-sectional root area or xylem cross-sectional area of individual roots. The combination of CT and LM will facilitate functional comparisons of woody roots differing in diameter and of tree species of different anatomical xylem structure.     

Development and variation of wood density, kraft pulp yield and fibre dimensions in young Norway spruce (Picea abies)

Important wood, pulp and fibre properties were investigated on small wood samples from two Rumanian, one German and one Norwegian provenance of Norway spruce (Picea abies) grown in Sørkedalen, Norway. Several samples were collected from inside each single tree, both in radial and transversal direction in the stem. Data were collected from a total of 59 trees, each 28 years of age. All investigated properties showed close relationship to ring number (RN) (cambium age). For basic density and fibre wall thickness (FWT), a fast decline was first observed when moving from pith to bark and a minimum value was found around RN 5–8. The declining trend was then followed by an increase. Kraft pulp yield, fibre length and fibre width (FW) also increased with RN, but the increase was most pronounced close to the pith. The pulp yield (PY) more or less stabilised outside of RN 5–6. FW showed a decrease outside of RN 10–12, but this was probably due to the remarkable simultaneous drop in ring width for the investigated trees. FW decreased, while basic density and fibre length increased with increasing height in the tree. PY and FWT were not affected by height in tree. Diameter at breast height (DBH) was the most important variable indicating differences between trees in the investigated material. Basic density, fibre length and FWT decreased, while FW increased with increasing DBH. Height to crown had a positive effect on basic density, but had no influence on any of the remaining properties. Differences between provenances were found for basic density, fibre length and FW. The analyses showed that it is possible to describe the variation inside and between trees satisfactorily for a range of important wood and fibre properties.     

Compositional changes of forest-floor vegetation in young stands of Norway spruce as an effect of repeated fertilisation

Forestry practices that aim to increase biomass production may mitigate climate change through increased carbon sequestration and the potential of substituting fossil fuels with renewable biofuels. Fertilising young stands of Norway spruce in Sweden have shown to increase tree growth by more than 200%. Fertilisation, however, also has other effects on forest ecosystems. Here, we studied the response of the species composition of forest-floor vegetation to three different frequencies of fertilisation in young stands of Norway spruce. Fertiliser was applied every year, every second year or every third year. The total amount of N ranged from 425 kg ha⁻¹ to 625 kg ha⁻¹, in combination with P, K, Ca, Mg, S, Mn, Zi, B and Cu. The largest effects of the fertilisation were found among bryophytes and lichens, which lost substantial cover. Unexpectedly, Deschampsia flexuosa, commonly known to be favoured by fertilisation, was negatively affected. Species that increased in frequency were Oxalis acetosella, Brachythecium sp. and Plagiothecium sp. Decreased availability of light, as an indirect effect of fertilisation through increased tree canopy cover, was found to be the most important factor behind the change in species composition of vascular plants. The total cover of bryophytes, however, did not show any significant response to the changes in canopy cover, indicating that the effects seen in this group may be a result of more direct effects of the fertiliser. Few significant differences were found between the two most intensive fertilisation frequencies, although fertilisation every third year was often distinguished from both the control and the other fertilised treatments. Even though the effects at the stand level were substantial, the effects on biodiversity and function of ecosystems on a landscape or regional level need further investigation.     

Regeneration niches of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> [L.] Karst.) saplings in small canopy gaps in mixed mountain forests of the Bavarian Limestone Alps

Natural regeneration measurements are the main silvicultural objective in overaged protective forests of the Bavarian Limestone Alps. While manifold problems with these stands, especially the impact of browsing, are widely recognised, the regeneration niches of Norway spruce (Picea abies [L.] Karst.) are insufficiently known. The purpose of this study was to determine favourable combinations of site factors for the development of spruce in small, unfenced canopy gaps, located on Aposerido-Fagetum caricetosum albae forest sites. We recorded the occurrence of spruce saplings (as dependent variable) and of six site factors (as independent variables) on 480 0.5 m²-subplots. In addition, we estimated the coverage of six acid adapted plant species to determine correlations with the humus depth. A binary logistic regression analysis was used to predict the probability of the occurrence of a spruce sapling in dependency of the different site factors. Supported by other studies, we assumed that the supply of solar radiation was adequate for the sufficient regeneration of spruce within the canopy gaps. Other site factors significantly determined the regeneration niches of spruce saplings. More spruce saplings were found near hindrances and on rough surfaces than would be expected from a random occurrence of saplings. These microsite types may have characteristics, especially protection against snow gliding that promotes spruce establishment. A calculated “hindrance index”, which accounted for the number, and the distance of surrounding hindrances might be a good specific value to describe the influence of hindrances on steep slopes. The sapling establishment decreased on thin humus layers. Our assumption for the sites was that thick organic layers might represent a good seedbed for spruce. Decayed dead wood was scarce, but was exceedingly favoured by spruce saplings. Results obtained suggest that the natural regeneration establishment of spruce on steep slopes can be successfully influenced by site factors which inhibit the influence of snow gliding. According to a “positive microsite” concept, we recommend for artificial regeneration measurements with spruce, microsites close to hindrances (e.g. stumps, downed trees) and Vaccinium myrtillus as a predictor for thick, acid humus layers.     

The effects of Douglas-fir on tree-specific arthropod communities in mixed species stands with European beech and Norway spruce

The ecological effects of planting exotic Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in Central Europe are still poorly understood. The aim of this study was to answer the question of whether Douglas-fir affects tree specific arthropod communities in different mature forest types (Douglas-fir, spruce and beech dominated) in Southern Germany. Therefore, arthropod communities of stem and tree crown strata of Douglas-fir and spruce (Picea abies L.) were sampled in the years 1999–2001 using arboreal photo-eclectors and flight interception traps. Statistical analysis was conducted for all species and focused on conifer specialists at three levels: (1) species diversity, (2) guild structure and (3) community structure. Within the stem stratum, species diversity was significantly higher on spruce than on Douglas-fir independent of year and stand composition. This could not be explained by a single feeding guild, rather by species changing strata during the vegetation period. In contrast, species diversity in tree crowns was approximately the same for both conifer species. However, communities in Douglas-fir crowns were conspicuously different from those in spruce crowns, especially in the Douglas-fir dominated stand type. While zoophagous insects exhibited higher activity on Douglas-fir in 2000, xylophagous beetles were more abundant on spruce in 2001. In European beech stands with widely spaced Douglas-fir trees, the site specific and broad-leaved tree related fauna might be maintained. In addition, Douglas-fir with its resource of Adelges cooleyi and crowns that overtop the broad-leaved tree canopy, offer additional resources for several aphidophagous and thermophile species.     

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.     

Variation of defence-related metabolites in the foliage of adult beech and spruce: a conceptual approach to approximating traded-off carbon

To prevent carbon (C) loss to consumers, trees need to defend their primary production. The tree-internal conflict in resource allocation between growth and defence demands has been the subject of various hypotheses but still requires quantification. A conceptual approach to approximating the C amount dispensable in favour of primary production at the expense of defence is demonstrated which is based on nine defence-related metabolite groups. Quantification is exemplified at the level of sun and shade leaves of adult Fagus sylvatica and Picea abies trees, two species contrasting in foliage type, under oxidative stress as induced by ozone exposure. The difference between maximum and minimum metabolite levels sampled several times throughout four consecutive growing seasons were conceived as dispensable between growth and defence-related metabolism and expressed in proportion of the mean annual gross primary production (GPP) of the foliage. In both species, this proportion amounted to between 2 and 5% of GPP (on a molar C basis). Remaining uncertainties are discussed as concerning functional overlap of substances between growth and defence-related metabolism, estimated classification of metabolite turnover rates and “third-party” trade-offs across C demands. Given the complexity of plant defence, simplification is needed for modelling allocation trade-offs in plants. The presented conceptual approach meets this need in approximating C transfer capacities between competing physiological demands and in stimulating empirical assessments towards mechanistic understanding. This article belongs to the special issue: “Growth and defence of Norway spruce and European beech in pure and mixed stands”.     

Crystallinity of wood and the size of cellulose crystallites in Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis>)

X-ray diffraction was used to study variations in the crystallinity of wood and the average thickness and length of the crystallites of cellulose as a function of the number of the year ring in Norway spruce [Picea abies (L.) Karst.]. The crystallinity increased from ring 4 to ring 10 from the pith and was constant after ring 10. The crystallinity of mature wood was about 30% ± 5%. The average thickness and average length of the crystallites were 3.2 ± 0.1nm and 28 ± 2nm, respectively; and no systematic variation of these values with the number of the year ring was observed. The mean microfibril angle decreased near the pith but was constant in the mature wood.