Tommy Mörling - Academia.edu (original) (raw)
Papers by Tommy Mörling
Holzforschung, 2016
Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement.... more Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (
Silva Fennica, 2007
Effects of combining lupin (Lupinus nootkatensis L.) establishment and soil scarification on stem... more Effects of combining lupin (Lupinus nootkatensis L.) establishment and soil scarification on stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) were studied on a poor boreal site in Sweden 18 years after plantation. A field randomized block experiment was established with three different scarification techniques (disc trenching, moulding and ploughing) followed by establishment of lupins by either seeds or roots. There were three blocks without and two blocks with lupins. Overall, on average for the three soil scarification techniques, the lupin treatment significantly increased the volume per hectare by 102%.The lupin treatment significantly increased the stem volume per hectare by 236% for mounding and 139% for disc trenching, whereas the 55% increase for ploughing was not significant. The increase in the total stem biomass yield per tree was more pronounced for larger trees; 46% for average trees and 106% for dominant trees. Howeve...
Holzforschung, 2003
Summary Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-m... more Summary Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-mm increment cores. The aim was to evaluate whether fibre length estimates from such small-diameter cores could be used to calculate genetic parameters, in spite of the increased amount of cut fibres produced at boring. The correlation between mean fibre lengths obtained from cores and sticks, with substantially fewer cut fibres, was high (r = 0.87, n = 53) and of the same magnitude as the correlation between samples from varied positions in the same tree (r = 0.87, n = 46). As regards evaluation of genetic tests and ranking for selection purposes, values from non-destructively sampled 5-mm cores from 0.5 m tree height appear to serve well. Fibre length development along annual ring classes started to differentiate between trees at annual rings 13–15, and after ring 16 there was a slight tendency towards stabilisation which may be interpreted as a reasonably advanced transition from juven...
Annals of Forest Science, 2002
Effects of nitrogen fertilisation and thinning, 40% basal area removal, on annual ring width and ... more Effects of nitrogen fertilisation and thinning, 40% basal area removal, on annual ring width and ring density were studied in a 2 × 2 factorial field experiment in northern Sweden, in an even aged 56-year-old Scots pine stand twelve years after treatment. Each treatment was replicated six times. From four stem heights, wood specimens were measured using direct scanning X-ray microdensitometry. For the whole period, mean ring width increased by 14% following fertilisation and by 40% after thinning. Neither fertilisation (< 1%) nor thinning (-4%) significantly (p > 0.05) changed ring density during the twelve-year period. Based on four-year mean values at 1.3 m, ring width increased in all cases, except for fertilisation in the last four-year period. The only significant effect on wood density was a 5% decrease following thinning during the second four-year period. Linear regression showed negative correlation between ring density and ring width and no additional effects of treatments per se. growth / Pinus sylvestris / wood density / X-ray densitometry Résumé-Évaluation de la largeur et de la densité des cernes après fertilisation et éclaircie dans un peuplement de pin sylvestre. Les effets de la fertilisation et de l'éclaircie sur la largeur et sur la densité des cernes ont été étudiés dans un peuplement expérimental du nord de la Suède, 12 ans après traitement, dans un peuplement équienne de pins sylvestres, âgé de 56 ans. Chaque traitement était répété six fois. Des échantillons de bois représentant deux rayons opposés ont été prélevés à quatre hauteurs et analysés par microdensitométrie scanning direct. Au cours des douze années après traitement, la largeur moyenne du cerne a augmenté de 14 % après fertilisation et de 40 % après éclaircie. Ni la fertilisation (< 1 %), ni l'éclaircie (-4 %) n'ont eu d'effect significatif (p > 0,05 %) sur la densité des cernes durant la période de douze ans. La largeur du cerne à 1,30 m, basée sur des moyennes de quatre ans, a augmenté dans tous les cas, sauf lors de la fertilisation pour la période des quatre dernières années. Le seul effet significatif sur la densité de bois était une diminution de 5 % suivant le traitement d'éclaircie durant la deuxième période de quatre ans. Une régression linéaire a démontré une corrélation négative entre la densité des cernes et la largeur du cerne et pas d'effet additionnel du traitement lui-même. accroissement radial / pin sylvestre / densité de bois / microdensitométrie
Holzforschung, 2003
Summary We propose a method to estimate fibre length distribution in conifers based on wood sampl... more Summary We propose a method to estimate fibre length distribution in conifers based on wood samples from increment cores processed by automatic optical fibre-analysers. Automatic fibre-analysers are unable to distinguish: a) fibres from other tissues, “fines”, and b) cut from uncut fibres. However, our proposed method can handle these problems if the type of distributions that fibre lengths and fines follow is known. In our study the length distributions of fines and fibres were assumed to follow truncated normal distributions, characterised by means and standard deviations of the two distributions. Parameter estimates were obtained by the maximum likelihood method. Wood samples from two 22-year-old Scots pine trees at breast height were used to evaluate the performance of the method. From stem discs at 1.5 m, adjacent samples of 5 mm increment cores and wood pieces were taken. The cores were trimmed 1 mm at each side and samples were, after maceration, analysed in a Kajaani FiberLa...
➢ Through the use of genome-wide association (GWAS) mapping it is possible to establish the genet... more ➢ Through the use of genome-wide association (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such an effort in Norway spruce (Picea abies (L). Karst.) for the traits related to wood tracheid characteristics.➢ The study employed an exome capture genotyping approach that generated 178 101 high quality Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a LASSO based association mapping method using a functional multi-locus mapping approach that utilizes latent traits, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). Expression of the identified candidate genes was examined using publicly available spruce databases.➢ The analysis have provided 31 loci and 26 mostly novel candidate genes, majority of which showing specific expression in wood-forming ti...
Forest Ecology and Management
Understanding historic development of multi-layered Scots pine (Pinus sylvestris L.) stands and h... more Understanding historic development of multi-layered Scots pine (Pinus sylvestris L.) stands and how they became multi-layered is essential for assessing the feasibility of using the selection system in these stands. To address this we measured trees (dbh ≥ 4 cm) and saplings (height > 0.5 m dbh < 4 cm) and used increment cores from 244 sample trees to reconstruct stand structure development, ingrowth and basal area increment in four multi-layered Scots pine stands in Sweden. Age distributions were quite homogeneous, three of the four stands had age distributions that were dominated by one or two 20 year age classes, suggesting that the irregular diameter distributions displayed in 2013 had developed from more homogeneous distributions. Analyses of the historical ingrowth of Scots pine into the tree layer suggested that the multi-layered structure was created by mass regeneration followed by size stratification caused by differences in growth rates within even-aged cohorts of regeneration. Large reductions of the basal area in the past resulted in abundant regeneration and ingrowth of Scots pine. When the over-story increased in basal area over time, there was a growth differentiation among the saplings and small trees, gradually creating a multi-layered stand structure as some of the trees grew into the larger size classes while others remained in the smaller size classes. When the stands reached a basal area of about 13 m 2 ha −1 the ingrowth of saplings past 1.3 m height essentially stopped but the size stratification among the small trees continued, further enhancing the multi-layered structure. The results indicate that to receive regeneration pulses and sustain a multi-layered structure in Scots pine forests, the basal area needs to be significantly reduced. The growth consequences of this need to be studied.
Tree Genetics & Genomes
Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a ... more Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a concern in conifer breeding programs. To evaluate the impact of selection for growth and solid-wood properties on fiber dimensions, we investigated the inheritance and efficiency of early selection for different wood-fiber traits and their correlations with stem diameter, wood density, modulus of elasticity (MOE), and microfibril angle (MFA) in Norway spruce (Picea abies L). The study was based on two large open-pollinated progeny trials established in southern Sweden in 1990 with material from 524 families comprising 5618 trees. Two increment cores were sampled from each tree. Radial variations from pith to bark were determined for rings 3-15 with SilviScan for fiber widths in the radial (RFW) and tangential (TFW) direction, fiber wall thickness (FWT), and fiber coarseness (FC). Fiber length (FL) was determined for rings 8-11. Heritabilities based on rings 8-11 using joint-site data were moderate to high (0.24-0.51) for all fiber-dimension traits. Heritabilities based on stem cross-sectional averages varied from 0.34 to 0.48 and reached a plateau at rings 6-9. The Bage-age^genetic correlations for RFW, TFW, FWT, and FC cross-sectional averages at a particular age with crosssectional averages at ring 15 reached 0.9 at rings 4-7. Our results indicated a moderate to high positive genetic correlation for density and MOE with FC and FWT, moderate and negative with RFW, and low with TFW and FL. Comparison of several selection scenarios indicated that the highest profitability is reached when diameter and MOE are considered jointly, in which case, the effect on any fiber dimension is negligible. Early selection was highly efficient from ring 5 for RFW and from rings 8-10 for TFW, FWT, and FC.
Canadian Journal of Forest Research
Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evalu... more Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evaluated in Norway spruce (Picea abies (L.) Karst) and lodgepole pine (Pinus contorta Douglas ex Loudon). Increment cores were collected at breast height (1.3 m) from 5664 trees in two 21-year-old Norway spruce progeny trials in southern Sweden and from 823 trees in two lodgepole pine progeny trials, aged 34–35 years, in northern Sweden. Radial variations in MFA from pith to bark were measured for each core using SilviScan. To estimate MFA transition from juvenile wood to mature wood, a threshold level of MFA 20° was considered, and six different regression functions were fitted to the MFA profile of each tree after exclusion of outliers, following three steps. The narrow-sense heritability estimates (h2) obtained for MFA transition were highest based on the slope function, ranging from 0.21 to 0.23 for Norway spruce and from 0.34 to 0.53 for lodgepole pine, while h2 were mostly non-signific...
Canadian Journal of Forest Research, 2016
Modelling studies have suggested that atmospheric nitrogen (N) deposition will increase forest ca... more Modelling studies have suggested that atmospheric nitrogen (N) deposition will increase forest carbon sequestration by stimulating tree growth. However, few long-term experiments studying N deposition effects on tree growth in boreal forests have been reported. This study empirically explores the relation between application rates of N, simulating levels of N deposition relevant for Europe, and the growth of Picea abies (L.) Karst. and Pinus sylvestris L. in a low N deposition area (<2 kg N·ha−1·year−1), we manually added 0, 12.5, and 50 kg N·ha−1·year−1 to a forest site dominated by P. abies for 19 years and 0, 3, 6, 12.5, and 50 kg N·ha−1·year−1 to a forest site dominated by P. sylvestris for 10 years. On both sites, linear regression analyses displayed significant relations between mean annual tree growth and N additions: P. abies relative growth rate increased by 1.2% per kg N added and that of P. sylvestris increased by 1.6% per kg N added. The growth response, however, varied over time, highlighting...
Silvae Genetica
Twelve trees in a 36 year old full-sib progeny plantation, testing a part of the Scots pine breed... more Twelve trees in a 36 year old full-sib progeny plantation, testing a part of the Scots pine breeding population, were analysed for wood density and the width of the earlywood and latewood sections in each annual ring. Wood samples (stem discs) were taken with 1 m intervals along the stem and the analyses covered thus the whole stem. Based on these data, the biomass of the earlywood and latewood of each annual ring in each 1 meter stem section was estimated. Latewood density increased from pith to bark while it decreased from stem base to top. Earlywood density was of similar size both radially and vertically. The biomass in each annual ring increased until around ring number 10 from pith for both wood types. For earlywood it then decreased while it remained quite constant for latewood. Latewood biomass decreased more rapidly towards the top of the tree than earlywood biomass. Heritabilities for earlywood and latewood in each annual ring at breast height (estimated in the same materi...
Forest Ecology and Management, 2015
Tree growth resources and the efficiency of resource-use for biomass production determine the pro... more Tree growth resources and the efficiency of resource-use for biomass production determine the productivity of forest ecosystems. In nutrient-limited forests, nitrogen (N)-fertilization increases foliage [N], which may increase photosynthetic rates, leaf area index (L), and thus light interception (I C). The product of such changes is a higher gross primary production and higher net primary production (NPP). However, fertilization may also alter carbohydrate partitioning from below-to aboveground, increasing aboveground NPP (ANPP). We analyzed effects of long-term N-fertilization on NPP, and that of long-term carbon storing organs (NPP S) in a Pinus sylvestris forest on sandy soil, a wide-ranging forest type in the boreal region. We based our analyses on a combination of destructive harvesting, consecutive mensuration, and optical measurements of canopy openness. After eight-year fertilization with a total of 70 g N m-2 , ANPP was 27 ± 7% higher in the fertilized (F) relative to the reference (R) stand, but although L increased relative to its pre-fertilization values, I C was not greater than in R. On the seventh year after the treatment initiation, the increase of ANPP was matched by the decrease of belowground NPP (78 vs. 92 g C m-2 yr-1 ; ~17% of NPP) and, given the similarity of I C , suggests that the main effect of N-fertilization was changed carbon partitioning rather than increased canopy photosynthesis. Annual NPP S increased linearly with growing season temperature (T) in both treatments, with an upward shift of 70.2 g C m-2 yr-1 by fertilization, which also caused greater amount of unexplained variation (r 2 = 0.53 in R, 0.21 in F). Residuals of the NPP S-T relationship of F were related to growing season precipitation (P, r 2 = 0.48), indicating that T constrains productivity at this site regardless of fertility, while P is important in determining productivity where N-limitation is alleviated. We estimated that, in a growing season average T (11.5 ± 1.0 °C; 33-year-mean), NPP S response to N-fertilization will be nullified with P 31 mm less than the mean (325 ± 85 mm), and would double with P 109 mm greater than the mean. These results suggest that inter-annual H. Lim et al. 3 variation in climate, particularly in P, may help explaining the reported large variability in growth responses to fertilization of pine stands on sandy soils. Furthermore, forest management of long-rotation systems, such as those of boreal and northern temperate forests, must consider the efficiency of fertilization in terms of wood production in the context of changes in climate predicted for the region.
Silva Fennica, 2013
Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in bo... more Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in boreal Scots pine Karlsson L., Mörling T., Bergsten U. (2013). Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in boreal Scots pine. Silva Fennica vol. 47 no. 4 article id 938. 17 p. Highlights • Initial stand densities have a large impact on the proportion of mature wood within trees throughout most of their life cycle. • The difference between regimes in volume of long fibres in crop trees could be substantial. • Long-term silvicultural strategies implemented at juvenile stand ages can be important tools in order to produce wood raw material suited for specific end-uses.
Forest ecology and …, 2007
Two field experiments, located in Central and Northern Sweden, were used to study the influence o... more Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 Â 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5-6.8 m 3 ha À1 year À1 for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha À1 year À1 , with an average of 14 and 21 stems ha À1 year À1 at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha À1 year À1 at the northern and southern site, respectively.
Forest ecology and management, 2000
Scandinavian Journal of Forest Research, 1999
The Forestry Chronicle, 2014
An experiment was established in a 38-year-old, mixed species stand with a 14.5-m birch overstory... more An experiment was established in a 38-year-old, mixed species stand with a 14.5-m birch overstory (Betula species) and a 3-m spruce understory (Picea abies). Treatments were birch shelterwood with 300 or 600 stems/ha and spruce understory with 1500 stems/ha, grown separately or mixed on 14 plots. Height growth of spruce was not significantly affected by birch shelterwood during a 36-year observation period, but spruce trees under birch shelter were more slender. Volume growth of spruce was slightly reduced by birch shelter, and volume growth of birch significantly reduced by a spruce understory. Total growth was higher for mixed than for single-species plots.
Holzforschung, 2016
Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement.... more Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (
Silva Fennica, 2007
Effects of combining lupin (Lupinus nootkatensis L.) establishment and soil scarification on stem... more Effects of combining lupin (Lupinus nootkatensis L.) establishment and soil scarification on stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) were studied on a poor boreal site in Sweden 18 years after plantation. A field randomized block experiment was established with three different scarification techniques (disc trenching, moulding and ploughing) followed by establishment of lupins by either seeds or roots. There were three blocks without and two blocks with lupins. Overall, on average for the three soil scarification techniques, the lupin treatment significantly increased the volume per hectare by 102%.The lupin treatment significantly increased the stem volume per hectare by 236% for mounding and 139% for disc trenching, whereas the 55% increase for ploughing was not significant. The increase in the total stem biomass yield per tree was more pronounced for larger trees; 46% for average trees and 106% for dominant trees. Howeve...
Holzforschung, 2003
Summary Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-m... more Summary Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-mm increment cores. The aim was to evaluate whether fibre length estimates from such small-diameter cores could be used to calculate genetic parameters, in spite of the increased amount of cut fibres produced at boring. The correlation between mean fibre lengths obtained from cores and sticks, with substantially fewer cut fibres, was high (r = 0.87, n = 53) and of the same magnitude as the correlation between samples from varied positions in the same tree (r = 0.87, n = 46). As regards evaluation of genetic tests and ranking for selection purposes, values from non-destructively sampled 5-mm cores from 0.5 m tree height appear to serve well. Fibre length development along annual ring classes started to differentiate between trees at annual rings 13–15, and after ring 16 there was a slight tendency towards stabilisation which may be interpreted as a reasonably advanced transition from juven...
Annals of Forest Science, 2002
Effects of nitrogen fertilisation and thinning, 40% basal area removal, on annual ring width and ... more Effects of nitrogen fertilisation and thinning, 40% basal area removal, on annual ring width and ring density were studied in a 2 × 2 factorial field experiment in northern Sweden, in an even aged 56-year-old Scots pine stand twelve years after treatment. Each treatment was replicated six times. From four stem heights, wood specimens were measured using direct scanning X-ray microdensitometry. For the whole period, mean ring width increased by 14% following fertilisation and by 40% after thinning. Neither fertilisation (< 1%) nor thinning (-4%) significantly (p > 0.05) changed ring density during the twelve-year period. Based on four-year mean values at 1.3 m, ring width increased in all cases, except for fertilisation in the last four-year period. The only significant effect on wood density was a 5% decrease following thinning during the second four-year period. Linear regression showed negative correlation between ring density and ring width and no additional effects of treatments per se. growth / Pinus sylvestris / wood density / X-ray densitometry Résumé-Évaluation de la largeur et de la densité des cernes après fertilisation et éclaircie dans un peuplement de pin sylvestre. Les effets de la fertilisation et de l'éclaircie sur la largeur et sur la densité des cernes ont été étudiés dans un peuplement expérimental du nord de la Suède, 12 ans après traitement, dans un peuplement équienne de pins sylvestres, âgé de 56 ans. Chaque traitement était répété six fois. Des échantillons de bois représentant deux rayons opposés ont été prélevés à quatre hauteurs et analysés par microdensitométrie scanning direct. Au cours des douze années après traitement, la largeur moyenne du cerne a augmenté de 14 % après fertilisation et de 40 % après éclaircie. Ni la fertilisation (< 1 %), ni l'éclaircie (-4 %) n'ont eu d'effect significatif (p > 0,05 %) sur la densité des cernes durant la période de douze ans. La largeur du cerne à 1,30 m, basée sur des moyennes de quatre ans, a augmenté dans tous les cas, sauf lors de la fertilisation pour la période des quatre dernières années. Le seul effet significatif sur la densité de bois était une diminution de 5 % suivant le traitement d'éclaircie durant la deuxième période de quatre ans. Une régression linéaire a démontré une corrélation négative entre la densité des cernes et la largeur du cerne et pas d'effet additionnel du traitement lui-même. accroissement radial / pin sylvestre / densité de bois / microdensitométrie
Holzforschung, 2003
Summary We propose a method to estimate fibre length distribution in conifers based on wood sampl... more Summary We propose a method to estimate fibre length distribution in conifers based on wood samples from increment cores processed by automatic optical fibre-analysers. Automatic fibre-analysers are unable to distinguish: a) fibres from other tissues, “fines”, and b) cut from uncut fibres. However, our proposed method can handle these problems if the type of distributions that fibre lengths and fines follow is known. In our study the length distributions of fines and fibres were assumed to follow truncated normal distributions, characterised by means and standard deviations of the two distributions. Parameter estimates were obtained by the maximum likelihood method. Wood samples from two 22-year-old Scots pine trees at breast height were used to evaluate the performance of the method. From stem discs at 1.5 m, adjacent samples of 5 mm increment cores and wood pieces were taken. The cores were trimmed 1 mm at each side and samples were, after maceration, analysed in a Kajaani FiberLa...
➢ Through the use of genome-wide association (GWAS) mapping it is possible to establish the genet... more ➢ Through the use of genome-wide association (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such an effort in Norway spruce (Picea abies (L). Karst.) for the traits related to wood tracheid characteristics.➢ The study employed an exome capture genotyping approach that generated 178 101 high quality Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a LASSO based association mapping method using a functional multi-locus mapping approach that utilizes latent traits, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). Expression of the identified candidate genes was examined using publicly available spruce databases.➢ The analysis have provided 31 loci and 26 mostly novel candidate genes, majority of which showing specific expression in wood-forming ti...
Forest Ecology and Management
Understanding historic development of multi-layered Scots pine (Pinus sylvestris L.) stands and h... more Understanding historic development of multi-layered Scots pine (Pinus sylvestris L.) stands and how they became multi-layered is essential for assessing the feasibility of using the selection system in these stands. To address this we measured trees (dbh ≥ 4 cm) and saplings (height > 0.5 m dbh < 4 cm) and used increment cores from 244 sample trees to reconstruct stand structure development, ingrowth and basal area increment in four multi-layered Scots pine stands in Sweden. Age distributions were quite homogeneous, three of the four stands had age distributions that were dominated by one or two 20 year age classes, suggesting that the irregular diameter distributions displayed in 2013 had developed from more homogeneous distributions. Analyses of the historical ingrowth of Scots pine into the tree layer suggested that the multi-layered structure was created by mass regeneration followed by size stratification caused by differences in growth rates within even-aged cohorts of regeneration. Large reductions of the basal area in the past resulted in abundant regeneration and ingrowth of Scots pine. When the over-story increased in basal area over time, there was a growth differentiation among the saplings and small trees, gradually creating a multi-layered stand structure as some of the trees grew into the larger size classes while others remained in the smaller size classes. When the stands reached a basal area of about 13 m 2 ha −1 the ingrowth of saplings past 1.3 m height essentially stopped but the size stratification among the small trees continued, further enhancing the multi-layered structure. The results indicate that to receive regeneration pulses and sustain a multi-layered structure in Scots pine forests, the basal area needs to be significantly reduced. The growth consequences of this need to be studied.
Tree Genetics & Genomes
Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a ... more Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a concern in conifer breeding programs. To evaluate the impact of selection for growth and solid-wood properties on fiber dimensions, we investigated the inheritance and efficiency of early selection for different wood-fiber traits and their correlations with stem diameter, wood density, modulus of elasticity (MOE), and microfibril angle (MFA) in Norway spruce (Picea abies L). The study was based on two large open-pollinated progeny trials established in southern Sweden in 1990 with material from 524 families comprising 5618 trees. Two increment cores were sampled from each tree. Radial variations from pith to bark were determined for rings 3-15 with SilviScan for fiber widths in the radial (RFW) and tangential (TFW) direction, fiber wall thickness (FWT), and fiber coarseness (FC). Fiber length (FL) was determined for rings 8-11. Heritabilities based on rings 8-11 using joint-site data were moderate to high (0.24-0.51) for all fiber-dimension traits. Heritabilities based on stem cross-sectional averages varied from 0.34 to 0.48 and reached a plateau at rings 6-9. The Bage-age^genetic correlations for RFW, TFW, FWT, and FC cross-sectional averages at a particular age with crosssectional averages at ring 15 reached 0.9 at rings 4-7. Our results indicated a moderate to high positive genetic correlation for density and MOE with FC and FWT, moderate and negative with RFW, and low with TFW and FL. Comparison of several selection scenarios indicated that the highest profitability is reached when diameter and MOE are considered jointly, in which case, the effect on any fiber dimension is negligible. Early selection was highly efficient from ring 5 for RFW and from rings 8-10 for TFW, FWT, and FC.
Canadian Journal of Forest Research
Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evalu... more Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evaluated in Norway spruce (Picea abies (L.) Karst) and lodgepole pine (Pinus contorta Douglas ex Loudon). Increment cores were collected at breast height (1.3 m) from 5664 trees in two 21-year-old Norway spruce progeny trials in southern Sweden and from 823 trees in two lodgepole pine progeny trials, aged 34–35 years, in northern Sweden. Radial variations in MFA from pith to bark were measured for each core using SilviScan. To estimate MFA transition from juvenile wood to mature wood, a threshold level of MFA 20° was considered, and six different regression functions were fitted to the MFA profile of each tree after exclusion of outliers, following three steps. The narrow-sense heritability estimates (h2) obtained for MFA transition were highest based on the slope function, ranging from 0.21 to 0.23 for Norway spruce and from 0.34 to 0.53 for lodgepole pine, while h2 were mostly non-signific...
Canadian Journal of Forest Research, 2016
Modelling studies have suggested that atmospheric nitrogen (N) deposition will increase forest ca... more Modelling studies have suggested that atmospheric nitrogen (N) deposition will increase forest carbon sequestration by stimulating tree growth. However, few long-term experiments studying N deposition effects on tree growth in boreal forests have been reported. This study empirically explores the relation between application rates of N, simulating levels of N deposition relevant for Europe, and the growth of Picea abies (L.) Karst. and Pinus sylvestris L. in a low N deposition area (<2 kg N·ha−1·year−1), we manually added 0, 12.5, and 50 kg N·ha−1·year−1 to a forest site dominated by P. abies for 19 years and 0, 3, 6, 12.5, and 50 kg N·ha−1·year−1 to a forest site dominated by P. sylvestris for 10 years. On both sites, linear regression analyses displayed significant relations between mean annual tree growth and N additions: P. abies relative growth rate increased by 1.2% per kg N added and that of P. sylvestris increased by 1.6% per kg N added. The growth response, however, varied over time, highlighting...
Silvae Genetica
Twelve trees in a 36 year old full-sib progeny plantation, testing a part of the Scots pine breed... more Twelve trees in a 36 year old full-sib progeny plantation, testing a part of the Scots pine breeding population, were analysed for wood density and the width of the earlywood and latewood sections in each annual ring. Wood samples (stem discs) were taken with 1 m intervals along the stem and the analyses covered thus the whole stem. Based on these data, the biomass of the earlywood and latewood of each annual ring in each 1 meter stem section was estimated. Latewood density increased from pith to bark while it decreased from stem base to top. Earlywood density was of similar size both radially and vertically. The biomass in each annual ring increased until around ring number 10 from pith for both wood types. For earlywood it then decreased while it remained quite constant for latewood. Latewood biomass decreased more rapidly towards the top of the tree than earlywood biomass. Heritabilities for earlywood and latewood in each annual ring at breast height (estimated in the same materi...
Forest Ecology and Management, 2015
Tree growth resources and the efficiency of resource-use for biomass production determine the pro... more Tree growth resources and the efficiency of resource-use for biomass production determine the productivity of forest ecosystems. In nutrient-limited forests, nitrogen (N)-fertilization increases foliage [N], which may increase photosynthetic rates, leaf area index (L), and thus light interception (I C). The product of such changes is a higher gross primary production and higher net primary production (NPP). However, fertilization may also alter carbohydrate partitioning from below-to aboveground, increasing aboveground NPP (ANPP). We analyzed effects of long-term N-fertilization on NPP, and that of long-term carbon storing organs (NPP S) in a Pinus sylvestris forest on sandy soil, a wide-ranging forest type in the boreal region. We based our analyses on a combination of destructive harvesting, consecutive mensuration, and optical measurements of canopy openness. After eight-year fertilization with a total of 70 g N m-2 , ANPP was 27 ± 7% higher in the fertilized (F) relative to the reference (R) stand, but although L increased relative to its pre-fertilization values, I C was not greater than in R. On the seventh year after the treatment initiation, the increase of ANPP was matched by the decrease of belowground NPP (78 vs. 92 g C m-2 yr-1 ; ~17% of NPP) and, given the similarity of I C , suggests that the main effect of N-fertilization was changed carbon partitioning rather than increased canopy photosynthesis. Annual NPP S increased linearly with growing season temperature (T) in both treatments, with an upward shift of 70.2 g C m-2 yr-1 by fertilization, which also caused greater amount of unexplained variation (r 2 = 0.53 in R, 0.21 in F). Residuals of the NPP S-T relationship of F were related to growing season precipitation (P, r 2 = 0.48), indicating that T constrains productivity at this site regardless of fertility, while P is important in determining productivity where N-limitation is alleviated. We estimated that, in a growing season average T (11.5 ± 1.0 °C; 33-year-mean), NPP S response to N-fertilization will be nullified with P 31 mm less than the mean (325 ± 85 mm), and would double with P 109 mm greater than the mean. These results suggest that inter-annual H. Lim et al. 3 variation in climate, particularly in P, may help explaining the reported large variability in growth responses to fertilization of pine stands on sandy soils. Furthermore, forest management of long-rotation systems, such as those of boreal and northern temperate forests, must consider the efficiency of fertilization in terms of wood production in the context of changes in climate predicted for the region.
Silva Fennica, 2013
Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in bo... more Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in boreal Scots pine Karlsson L., Mörling T., Bergsten U. (2013). Influence of silvicultural regimes on the volume and proportion of juvenile and mature wood in boreal Scots pine. Silva Fennica vol. 47 no. 4 article id 938. 17 p. Highlights • Initial stand densities have a large impact on the proportion of mature wood within trees throughout most of their life cycle. • The difference between regimes in volume of long fibres in crop trees could be substantial. • Long-term silvicultural strategies implemented at juvenile stand ages can be important tools in order to produce wood raw material suited for specific end-uses.
Forest ecology and …, 2007
Two field experiments, located in Central and Northern Sweden, were used to study the influence o... more Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 Â 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5-6.8 m 3 ha À1 year À1 for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha À1 year À1 , with an average of 14 and 21 stems ha À1 year À1 at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha À1 year À1 at the northern and southern site, respectively.
Forest ecology and management, 2000
Scandinavian Journal of Forest Research, 1999
The Forestry Chronicle, 2014
An experiment was established in a 38-year-old, mixed species stand with a 14.5-m birch overstory... more An experiment was established in a 38-year-old, mixed species stand with a 14.5-m birch overstory (Betula species) and a 3-m spruce understory (Picea abies). Treatments were birch shelterwood with 300 or 600 stems/ha and spruce understory with 1500 stems/ha, grown separately or mixed on 14 plots. Height growth of spruce was not significantly affected by birch shelterwood during a 36-year observation period, but spruce trees under birch shelter were more slender. Volume growth of spruce was slightly reduced by birch shelter, and volume growth of birch significantly reduced by a spruce understory. Total growth was higher for mixed than for single-species plots.