Deciding how to establish woodland in forest restoration is not straightforward as different outc... more Deciding how to establish woodland in forest restoration is not straightforward as different outcomes may be obtained from different establishment approaches, each with cost implications and degree of success limitations attached. Planning restoration requires knowledge of site conditions, including how sites are likely to respond under climate change. For objectives of production and high timber quality it is likely that ground preparation will be used, and planting with forest reproductive material (FRM) of known traits, such as: high survival and growth in establishment, drought tolerance adequate for climate projections, good resistance to pests and pathogens. For objectives associated with biodiversity, carbon sequestration, water supply protection, soil protection, natural regeneration could be a less costly solution with a limited amount of assisted translocation of selected FRM to improve resilience. If objectives are for rewilding forest areas, a degree of natural colonisat...
Forestry: An International Journal of Forest Research, 2021
Genetic variances are important parameters and have a great impact on the determination of optima... more Genetic variances are important parameters and have a great impact on the determination of optimal breeding strategies of tree species. A large clonal testing program was conducted to estimate additive, dominant and epistatic variances for the development of breeding and deployment strategies in Norway spruce (Picea abies (L.) Karst.). The analysis results of genetic variation for growth and wood properties in two clonal trials in central Sweden indicated that the important sources of total genetic variation were both additive and non-additive genetic variances. Additive genetic variation accounted for the majority of total genetic variation for diameter at breast height (DBH) and wood quality traits, whereas non-additive genetic variation was significant only for tree height at an early age. Predicted genetic gain was the highest for clonal deployment based on best tested (replicated) clones (4.7–65.3 per cent), followed by clonal deployment of the best individual trees from a full...
Norway spruce (Picea abies) is a dominant conifer species of major economic importance in Norther... more Norway spruce (Picea abies) is a dominant conifer species of major economic importance in Northern Europe. Extensive breeding programs were established to improve phenotypic traits of economic interest. In southern Sweden seeds used to create progeny tests were collected on about 3000 trees of outstanding phenotype (“plus” trees) across the region. In a companion paper (Chen et al., 2019) we showed that some were of local origin but many were recent introductions from the rest of the natural range. The mixed origin of the trees together with partial sequencing of the exome of >1,500 of these trees and phenotypic data retrieved from the Swedish breeding program offered a unique opportunity to dissect the genetic basis of local adaptation of three quantitative traits (height, diameter and budburst) and assess the potential of assisted gene flow. Through a combination of multivariate analyses and genome-wide association studies, we showed that there was a very strong effect of geographical origin on growth (height and diameter) and phenology (budburst) with trees from southern origins outperforming local provenances. Association studies revealed that growth traits were highly polygenic and budburst somewhat less. Hence, our results suggest that assisted gene flow and genomic selection approaches could help to alleviate the effect of climate change on P. abies breeding programs in Sweden
Vast population movements induced by recurrent climatic cycles have shaped the genetic structure ... more Vast population movements induced by recurrent climatic cycles have shaped the genetic structure of plant species. This is especially true in Scandinavia that was repeatedly glaciated. During glacial periods trees were confined to refugia, south and east of the ice sheet, from which they recolonized Scandinavia as the ice melted away. This multi-pronged recolonization led to large contact zones in most species. We leverage large genomic data from 5000 trees to reconstruct the demographic history of Norway spruce (Picea abies) and test for the presence of natural selection during the recolonization process and the establishment of the contact zone. Sweden is today made up of two large genetic clusters, a southern one originating from the Baltics and a Northern one originating from Northern Russia. The contact zone delineating these two clusters closely matches the limit between two major climatic regions. This suggests that natural selection contributed to the establishment and the m...
Population genetic structure matters for a large range of issues: it is intrinsically related to ... more Population genetic structure matters for a large range of issues: it is intrinsically related to speciation and local adaptation, it informs us on past demography, it conditions the response of pop ...
Forests provide important ecosystem services and renewable materials. Yet, under a future climate... more Forests provide important ecosystem services and renewable materials. Yet, under a future climate, optimal conditions will likely shift outside the current range for some tree species. This will challenge the persistence of populations to rely on inherent plasticity and genetic diversity to acclimate or adapt to future uncertain conditions. An opportunity to study such processes is offered by Scots pine (Pinus sylvestris L.), a forest tree with a large distribution range including populations locally adapted to a wide variety of environments, which hinders a range-wide assessment of the species to climate change. Here we evaluate tree height growth uncertainty of Scots pine marginal populations in Spain and the Nordic countries linked to their genetic adaptation promoted by different climatic drivers. Our aims are to: (i) review the main climatic drivers of Scots pine adaptation across its range; (ii) undertake provenance-based modeling and prediction of tree height under current an...
In 2018, up to 4 million m 3 Norway spruce was killed by the spruce bark beetle Ips typographus i... more In 2018, up to 4 million m 3 Norway spruce was killed by the spruce bark beetle Ips typographus in Sweden. The event was unique for Sweden, in terms of both affected volume and the fact that it was triggered by severe drought stress, not by ample availability of relatively defenseless storm-felled trees. The outbreak continued in 2019 and 2020, each year with twice as many trees killed as in 2018. The aim of this study was to quantify seasonal variation and potential lag-effects in tree defense capacity the year after a severe drought stress. Inoculation with a bark beetle-associated bluestain fungus, repeated four times with one-month-intervals between May and August 2019, were carried out at three field sites with spruce provenances of Swedish and East European origin representing early and late bud burst, respectively. All sites had experienced moderate to severe drought stress in 2018, and site-specific defense capacity correlated positively with the cumulative precipitation two months before inoculation. Sites with two-month precipitation levels <100 mm had larger necrotic lesions in the phloem following inoculation, an indication of lower tree defense capacity. Lesion size did not differ between provenances, and all trees were able to confine fungal infection successfully. There were some seasonal differences in necrotic lesion size, with the sites Skärsnäs and Norberg having significantly larger lesions in June than in May, and site Lugnet having large lesions also in May. Lesions were generally smaller in July and August than in June. The cross-sectional area and number of traumatic resin ducts was measured in sapwood samples from one site, Lugnet, to quantify an additional aspect of tree defenses. The area of resin ducts produced in May and June were larger than that in July and August. This is in line with a positive correlation between lesion area and resin duct area, indicating that a stronger fungal infection following inoculation in spring triggered a stronger induced defense response. The East European provenances had more resin ducts than Swedish provenances, but the area of resin ducts did not differ significantly between provenances.
The aim of this study was to develop a Scots pine (Pinus sylvestris L.) breeding objective for a ... more The aim of this study was to develop a Scots pine (Pinus sylvestris L.) breeding objective for a vertically integrated sawmill in northern Sweden. The production system was defined as comprising the sawmill and the forests supplying it. Volume per hectare, wood density, survival and straightness were used as objective traits and the related selection criteria were measurements, collected at young tree age, of height, diameter, pilodyn penetration, vitality and straightness. A bio-economic model was used to calculate economic weights for the objective traits identified. We also investigated the efficiency of different selection indices based on these economic weights, in combination with available data on genetic parameters. Furthermore, we studied the effect of different discount rates on the calculated economic weights. The results showed that, compared to the full index (which included all selection criteria), omitting either vitality or straightness had a negligible effect, reduc...
The summer drought of 2018 was one of the most climatically severe events in Europe that led to r... more The summer drought of 2018 was one of the most climatically severe events in Europe that led to record-breaking temperatures and wildfires in many parts of Europe. The main objective of this study was to assess the impact of the 2018 drought on the phenotypic and genetic response of Norway spruce height growth using the Standardized Precipitation-Evapotranspiration Index (SPEI). To achieve this, the total cumulative height growth of about 6000 clones from 2016 to 2019 in four full-sib trials in Sweden, aged 6–7 years, and from 2017 to 2019 in two half-sib trials in Finland, aged 8–9 years, were measured. The results indicate that the 2018 drought caused reductions in the increment of trees. Although heritability estimates were similar to other reports for Norway spruce, the additive genetic variance was highly inflated in one of the visibly drought-damaged trials in Southern Sweden. Similarly, the genotype by environment (G × E) interaction was highly significant in the drought-dama...
The aim of this study was to analyze and compare the performance of Norway spruce seed sources fr... more The aim of this study was to analyze and compare the performance of Norway spruce seed sources from Swedish stands of East European origin (SweEast) with material from Swedish (SweSO) and East European (EastSO) seed orchards, and with material from Swedish (SweS) and East European (EastS) unimproved stands. The seed sources were field tested at six locations in southern Sweden and assessed for growth and phenology. The assessment of growth traits indicated that trees from SweSO and EastSO had 9-15% greater growth with respect to tree height and diameter in comparison to trees from Swedish local unimproved stands (SweS). Trees from SweEast and EastS showed around 5-7% greater growth. With respect to phenological traits, the expected later bud burst for EastS and EastSO in comparison to SweS, SweSO and SweEast was verified. However, SweEast exhibited earlier bud burst compared to EastS than what could be explained by pollination by Swedish pollen. This was explained by early land race formation for that trait. A strong positive correlation was observed between bud burst and frost damage, which indicates that earlier bud burst does indeed increase the risk of damage from late spring frost at frost-prone sites.
Key message There is considerable genetic gain of tree volume from clonal deployment in Norway sp... more Key message There is considerable genetic gain of tree volume from clonal deployment in Norway spruce (Picea abies(L.) H. Karst) and clonal deployment will have at least 50% more or double genetic gain than the seedling deployment. Context Genetic parameters and genetic gains for wood quality and growth traits were estimated in six large clonal progeny trials. Aims Develop the optimal clonal deployment strategy of Norway spruce in Sweden. Methods Wood quality and growth traits were measured in all clonal trials and additive and non-additive genetic variances are partitioned. Results Additive and non-additive genetic variances were equally important for growth traits while non-additive variance was small or not significant for wood quality trait. The genetic gain predicted for clonal deployment was greater than any of the other four deployment strategies. Selecting the top 1% of tested clones (clonal forestry) would have 48.4% and 134.6% more gain than the gain predicted for the seed...
Deciding how to establish woodland in forest restoration is not straightforward as different outc... more Deciding how to establish woodland in forest restoration is not straightforward as different outcomes may be obtained from different establishment approaches, each with cost implications and degree of success limitations attached. Planning restoration requires knowledge of site conditions, including how sites are likely to respond under climate change. For objectives of production and high timber quality it is likely that ground preparation will be used, and planting with forest reproductive material (FRM) of known traits, such as: high survival and growth in establishment, drought tolerance adequate for climate projections, good resistance to pests and pathogens. For objectives associated with biodiversity, carbon sequestration, water supply protection, soil protection, natural regeneration could be a less costly solution with a limited amount of assisted translocation of selected FRM to improve resilience. If objectives are for rewilding forest areas, a degree of natural colonisat...
Forestry: An International Journal of Forest Research, 2021
Genetic variances are important parameters and have a great impact on the determination of optima... more Genetic variances are important parameters and have a great impact on the determination of optimal breeding strategies of tree species. A large clonal testing program was conducted to estimate additive, dominant and epistatic variances for the development of breeding and deployment strategies in Norway spruce (Picea abies (L.) Karst.). The analysis results of genetic variation for growth and wood properties in two clonal trials in central Sweden indicated that the important sources of total genetic variation were both additive and non-additive genetic variances. Additive genetic variation accounted for the majority of total genetic variation for diameter at breast height (DBH) and wood quality traits, whereas non-additive genetic variation was significant only for tree height at an early age. Predicted genetic gain was the highest for clonal deployment based on best tested (replicated) clones (4.7–65.3 per cent), followed by clonal deployment of the best individual trees from a full...
Norway spruce (Picea abies) is a dominant conifer species of major economic importance in Norther... more Norway spruce (Picea abies) is a dominant conifer species of major economic importance in Northern Europe. Extensive breeding programs were established to improve phenotypic traits of economic interest. In southern Sweden seeds used to create progeny tests were collected on about 3000 trees of outstanding phenotype (“plus” trees) across the region. In a companion paper (Chen et al., 2019) we showed that some were of local origin but many were recent introductions from the rest of the natural range. The mixed origin of the trees together with partial sequencing of the exome of >1,500 of these trees and phenotypic data retrieved from the Swedish breeding program offered a unique opportunity to dissect the genetic basis of local adaptation of three quantitative traits (height, diameter and budburst) and assess the potential of assisted gene flow. Through a combination of multivariate analyses and genome-wide association studies, we showed that there was a very strong effect of geographical origin on growth (height and diameter) and phenology (budburst) with trees from southern origins outperforming local provenances. Association studies revealed that growth traits were highly polygenic and budburst somewhat less. Hence, our results suggest that assisted gene flow and genomic selection approaches could help to alleviate the effect of climate change on P. abies breeding programs in Sweden
Vast population movements induced by recurrent climatic cycles have shaped the genetic structure ... more Vast population movements induced by recurrent climatic cycles have shaped the genetic structure of plant species. This is especially true in Scandinavia that was repeatedly glaciated. During glacial periods trees were confined to refugia, south and east of the ice sheet, from which they recolonized Scandinavia as the ice melted away. This multi-pronged recolonization led to large contact zones in most species. We leverage large genomic data from 5000 trees to reconstruct the demographic history of Norway spruce (Picea abies) and test for the presence of natural selection during the recolonization process and the establishment of the contact zone. Sweden is today made up of two large genetic clusters, a southern one originating from the Baltics and a Northern one originating from Northern Russia. The contact zone delineating these two clusters closely matches the limit between two major climatic regions. This suggests that natural selection contributed to the establishment and the m...
Population genetic structure matters for a large range of issues: it is intrinsically related to ... more Population genetic structure matters for a large range of issues: it is intrinsically related to speciation and local adaptation, it informs us on past demography, it conditions the response of pop ...
Forests provide important ecosystem services and renewable materials. Yet, under a future climate... more Forests provide important ecosystem services and renewable materials. Yet, under a future climate, optimal conditions will likely shift outside the current range for some tree species. This will challenge the persistence of populations to rely on inherent plasticity and genetic diversity to acclimate or adapt to future uncertain conditions. An opportunity to study such processes is offered by Scots pine (Pinus sylvestris L.), a forest tree with a large distribution range including populations locally adapted to a wide variety of environments, which hinders a range-wide assessment of the species to climate change. Here we evaluate tree height growth uncertainty of Scots pine marginal populations in Spain and the Nordic countries linked to their genetic adaptation promoted by different climatic drivers. Our aims are to: (i) review the main climatic drivers of Scots pine adaptation across its range; (ii) undertake provenance-based modeling and prediction of tree height under current an...
In 2018, up to 4 million m 3 Norway spruce was killed by the spruce bark beetle Ips typographus i... more In 2018, up to 4 million m 3 Norway spruce was killed by the spruce bark beetle Ips typographus in Sweden. The event was unique for Sweden, in terms of both affected volume and the fact that it was triggered by severe drought stress, not by ample availability of relatively defenseless storm-felled trees. The outbreak continued in 2019 and 2020, each year with twice as many trees killed as in 2018. The aim of this study was to quantify seasonal variation and potential lag-effects in tree defense capacity the year after a severe drought stress. Inoculation with a bark beetle-associated bluestain fungus, repeated four times with one-month-intervals between May and August 2019, were carried out at three field sites with spruce provenances of Swedish and East European origin representing early and late bud burst, respectively. All sites had experienced moderate to severe drought stress in 2018, and site-specific defense capacity correlated positively with the cumulative precipitation two months before inoculation. Sites with two-month precipitation levels <100 mm had larger necrotic lesions in the phloem following inoculation, an indication of lower tree defense capacity. Lesion size did not differ between provenances, and all trees were able to confine fungal infection successfully. There were some seasonal differences in necrotic lesion size, with the sites Skärsnäs and Norberg having significantly larger lesions in June than in May, and site Lugnet having large lesions also in May. Lesions were generally smaller in July and August than in June. The cross-sectional area and number of traumatic resin ducts was measured in sapwood samples from one site, Lugnet, to quantify an additional aspect of tree defenses. The area of resin ducts produced in May and June were larger than that in July and August. This is in line with a positive correlation between lesion area and resin duct area, indicating that a stronger fungal infection following inoculation in spring triggered a stronger induced defense response. The East European provenances had more resin ducts than Swedish provenances, but the area of resin ducts did not differ significantly between provenances.
The aim of this study was to develop a Scots pine (Pinus sylvestris L.) breeding objective for a ... more The aim of this study was to develop a Scots pine (Pinus sylvestris L.) breeding objective for a vertically integrated sawmill in northern Sweden. The production system was defined as comprising the sawmill and the forests supplying it. Volume per hectare, wood density, survival and straightness were used as objective traits and the related selection criteria were measurements, collected at young tree age, of height, diameter, pilodyn penetration, vitality and straightness. A bio-economic model was used to calculate economic weights for the objective traits identified. We also investigated the efficiency of different selection indices based on these economic weights, in combination with available data on genetic parameters. Furthermore, we studied the effect of different discount rates on the calculated economic weights. The results showed that, compared to the full index (which included all selection criteria), omitting either vitality or straightness had a negligible effect, reduc...
The summer drought of 2018 was one of the most climatically severe events in Europe that led to r... more The summer drought of 2018 was one of the most climatically severe events in Europe that led to record-breaking temperatures and wildfires in many parts of Europe. The main objective of this study was to assess the impact of the 2018 drought on the phenotypic and genetic response of Norway spruce height growth using the Standardized Precipitation-Evapotranspiration Index (SPEI). To achieve this, the total cumulative height growth of about 6000 clones from 2016 to 2019 in four full-sib trials in Sweden, aged 6–7 years, and from 2017 to 2019 in two half-sib trials in Finland, aged 8–9 years, were measured. The results indicate that the 2018 drought caused reductions in the increment of trees. Although heritability estimates were similar to other reports for Norway spruce, the additive genetic variance was highly inflated in one of the visibly drought-damaged trials in Southern Sweden. Similarly, the genotype by environment (G × E) interaction was highly significant in the drought-dama...
The aim of this study was to analyze and compare the performance of Norway spruce seed sources fr... more The aim of this study was to analyze and compare the performance of Norway spruce seed sources from Swedish stands of East European origin (SweEast) with material from Swedish (SweSO) and East European (EastSO) seed orchards, and with material from Swedish (SweS) and East European (EastS) unimproved stands. The seed sources were field tested at six locations in southern Sweden and assessed for growth and phenology. The assessment of growth traits indicated that trees from SweSO and EastSO had 9-15% greater growth with respect to tree height and diameter in comparison to trees from Swedish local unimproved stands (SweS). Trees from SweEast and EastS showed around 5-7% greater growth. With respect to phenological traits, the expected later bud burst for EastS and EastSO in comparison to SweS, SweSO and SweEast was verified. However, SweEast exhibited earlier bud burst compared to EastS than what could be explained by pollination by Swedish pollen. This was explained by early land race formation for that trait. A strong positive correlation was observed between bud burst and frost damage, which indicates that earlier bud burst does indeed increase the risk of damage from late spring frost at frost-prone sites.
Key message There is considerable genetic gain of tree volume from clonal deployment in Norway sp... more Key message There is considerable genetic gain of tree volume from clonal deployment in Norway spruce (Picea abies(L.) H. Karst) and clonal deployment will have at least 50% more or double genetic gain than the seedling deployment. Context Genetic parameters and genetic gains for wood quality and growth traits were estimated in six large clonal progeny trials. Aims Develop the optimal clonal deployment strategy of Norway spruce in Sweden. Methods Wood quality and growth traits were measured in all clonal trials and additive and non-additive genetic variances are partitioned. Results Additive and non-additive genetic variances were equally important for growth traits while non-additive variance was small or not significant for wood quality trait. The genetic gain predicted for clonal deployment was greater than any of the other four deployment strategies. Selecting the top 1% of tested clones (clonal forestry) would have 48.4% and 134.6% more gain than the gain predicted for the seed...
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