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Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2024

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Abstract

Climate change threatens the role of European forests as a long-term carbon sink. Assisted migration aims to increase the resilience of forest tree populations to climate change, using species-specific climatic limits and local adaptations through transferring seed provenances. We modelled assisted migration scenarios for seven main European tree species and analysed the effects of species and seed provenance selection, accounting for environmental and genetic variations, on the annual above-ground carbon sink of regrowing juvenile forests. To increase forest resilience, coniferous trees need to be replaced by deciduous species over large parts of their distribution. If local seed provenances are used, this would result in a decrease of the current carbon sink (40 TgC yr−1) by 34–41% by 2061–2080. However, if seed provenances adapted to future climates are used, current sinks could be maintained or even increased to 48–60 TgC yr−1.

Abstract

Female flowering and cone production took place in three Norway spruce progeny tests at ages 17 and 20 years, each planted with full-sib families from a half diallel. The number of cones on individual trees were scored in five classes. More than 50 % of the trees produced cones, and a considerable variation was found among families for the ability to produce cones (precocity) and for the number of clones scored in classes (fruitfulness). Both traits were strongly related to tree heights and diameters at the individual and at the family level. In general, tall trees produced the highest number of cones. However, some families produced many cones even if their average heights were low. In two of the half diallels, estimates of GCA variance components for the number of cones produced had twice the value of the SCA component, indicating additive genetic inheritance of cone production. Heritability estimates of cone scores were 0.10, 0.17 and 0.23, and the genetic correlations between cone production and tree heights were 0.40, 0.50 and 0.35 in the three half-diallels, respectively.

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Abstract

Drought hardening is a nursery technique aimed to enhance early forest plantation establishment under dry conditions, which is a main limiting factors for plantation success. However, the quantitative effectiveness of drought hardening remains unclear. We conducted a meta-analysis to evaluate the influence of different factors in the effectiveness of drought hardening on seedling post-planting survival and growth. Overall, drought hardening did not significantly affect survival or growth, as several factors induced great heterogeneity, but analyses of those factors explained its effectiveness, especially on survival. A longer time between hardening and transplanting strongly reduced survival. Indoor-grown seedlings did not benefit more from hardening than outdoor-grown seedlings. Evaluations of drought hardening effectiveness in pots showed positive effects on survival but negative effects on growth, while no effects were found in large bed experiments. In field experiments, hardening significantly increased survival and growth with site aridity. Survival benefits were independent of species drought tolerance, measured by osmotic potential at the turgor loss point (πtlp), in moderate to high aridity sites. However, in low aridity sites, hardening increased survival in drought-tolerant species but decreased it in drought-intolerant species. Field results showed that hardening benefited shrubs more than trees in angiosperms. In conclusion, drought hardening at the end of nursery cultivation tend to increase post-planting seedling performance particularly in scenarios limiting post-planting root growth such as in arid climates and pot experiments. Our findings highlight the importance of future research on modelling the interaction between these technical features and species water use strategies..

Abstract

Scots pine (Pinus sylvestris L.) is a commercially important forest tree species in many Eurasian countries. Its wood has been commonly utilized for production of construction timber. In Sweden, a breeding program was launched in 1950s to improve Scots pine trees to better suit industrial requirements. The emphasis was mainly put on improving stem volume, vitality, stem straightness and branching characteristics whilst wood quality was neglected. However, since some of the important wood quality traits are negatively correlated with the prioritized volume production, the continuation of such an approach could in a long run lead to irreversible deterioration of wood quality. In our study, we focused on wood quality traits that are relevant for construction timber – wood density, stiffness, strength, grain angle and sawn-board shape stability (crook, bow and twist). We linked wood quality traits nondestructively assessed on standing trees with those measured on sawn boards. We estimated narrow-sense heritabilities, genetic correlations and correlated responses to selection with the aim of identifying reliable techniques for wood quality assessment on standing trees and proposing suitable strategies for incorporating wood quality traits into the breeding program. We have concluded that standing-tree drilling resistance, acoustic velocity and grain angle are good predictors of wood density, wood stiffness & strength, and sawn-board twisting, respectively. Taking into account the long-term development on wood market, we are proposing an inclusion of wood density in the breeding program, in the way that it will be retained at the current levels rather than increased, which would also positively affect wood stiffness and strength. Furthermore, we are suggesting to consider grain angle as a breeding trait although more research is needed to unravel its underlying biological mechanism.

Abstract

Forest tree seed orchards are artificial populations of genetically superior individuals that play a crucial role in the production of high-quality seeds for reforestation and afforestation programs worldwide. In the pre-genetic-marker era, seed orchards were assumed to act as closed, panmictic populations with equal reproductive success among parents and with no gene flow from external pollen sources. Meeting these assumptions would ensure that the genetic gain attained by breeding would be efficiently transmitted to the next generation, i.e., into seed orchard crops. Many studies published to date have shown that parental reproductive success may be highly variable and that gene flow from undesired pollen sources, a.k.a. pollen contamination, can be substantial. Since the realized genetic gain can be considerably reduced, it is important to monitor mating patterns in seed orchards and thereby control the genetic quality (gain and diversity) of their crops. With the development of genetic markers, the theoretical assumptions as well as the efficiency of measures proposed to enhance desired crosses and reduce pollen contamination in seed orchards could be verified. First attempts to unravel mating patterns and quantify pollen contamination in seed orchards date back to the late 1970s when allozyme markers were introduced. Allozymes remained in use for over two decades, but due to their low resolution, they were gradually replaced with much more powerful microsatellites (SSRs), which, along with the rapid evolution of various statistical approaches, were capable of providing a much more detailed picture of seed orchards’ mating dynamics through pedigree reconstruction. Recently, SNP arrays that have been (and are being) developed for a number of commercially important forest tree species make it possible to affordably and rapidly screen seed orchard seed lots and evaluate the orchards’ genetic efficiency.

Abstract

The boreal, alpine, and arctic heaths and forests are dominated by dwarf-shrubs along with their symbionts, ericoid mycorrhizal fungi. Dwarf-shrubs are sensitive to climate change and are already affected in large-scale diebacks. It remains to explore how their mycorrhizal symbionts mitigate damages, since little is known about these plant-fungal interactions. Ericoid mycorrhizal fungi are known to aid the host plant with nutrient uptake, but little research exists on their dealings with drought, suggesting a major knowledge gap. A better overview of belowground ericoid fungi at different drought levels might help predict future climate-change induced damage. In our study we aim to find out if and how drought affects ericoid mycorrhizal fungal communities, and pinpoint key species related to drought mitigation.

Abstract

The boreal, alpine, and arctic heaths and forests are dominated by dwarf-shrubs along with their symbionts, ericoid mycorrhizal fungi. Dwarf-shrubs are sensitive to climate change and are already affected in large-scale diebacks. It remains to explore how their mycorrhizal symbionts mitigate damages, since little is known about these plant-fungal interactions. Ericoid mycorrhizal fungi are known to aid the host plant with nutrient uptake, but little research exists on their dealings with drought, suggesting a major knowledge gap. A better overview of belowground ericoid fungi at different drought levels might help predict future climate-change induced damage. In our study we aim to find out if and how drought affects ericoid mycorrhizal fungal communities, and pinpoint key species related to drought mitigation.

To document

Abstract

Polyploidy, or genome doubling, has occurred repeatedly through plant evolution. While polyploid plants are used extensively in agriculture and horticulture, they have so far found limited use in forestry. Here we review the potentials of polyploid trees under climate change, and investigate if there is support for increased use. We find that polyploid trees like other plants have consistent increases in cell sizes compared to diploids, and that leaf-area based rates of photosynthesis tend to increase with increasing levels of ploidy. While no particular trend could be discerned in terms of biomass between trees of different ploidy levels, physiology is affected by polyploidization and several studies point towards a high potential for polyploid trees to adapt to drought stress. The ploidy level of most tree species is unknown, and analysis of geographical patterns in frequencies of polyploid trees are inconclusive. Artificial polyploid trees are often created by colchicine and in a few cases these have been successfully applied in forestry, but the effects of induced polyploidization in many economically important tree species remains untested. Polyploids would also be increasingly useful in tree breeding programs, to create synthetic hybrids or sterile triploids that could control unwanted spreading of germplasm in nature. In conclusion, this review suggests that polyploid trees may be superior under climate change in some cases, but that the potential of polyploids is not yet fully known and should be evaluated on a case-to-case basis for different tree species.