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The genus L. is composed of several species, which are difficult to distinguish in the field on the basis of morphological traits. The aim of this study was to evaluate the taxonomic importance of using visible + near infrared (Vis + NIR) spectra of single seeds for differentiating Roth and Ehrh. Seeds from several families (controlled crossings of known parent trees) of each species were used and Vis + NIR reflectance spectra were obtained from single seeds. Multivariate discriminant models were developed by Orthogonal Projections to Latent Structures â Discriminant Analysis (OPLS-DA). The OPLS-DA model fitted on Vis + NIR spectra recognized with 100% classification accuracy while the prediction accuracy of class membership for was 99%. However, the discriminant models fitted on NIR spectra alone resulted in 100% classification accuracies for both species. Absorption bands accounted for distinguishing between birch species were attributed to differences in color and chemical composition, presumably polysaccharides, proteins and fatty acids, of the seeds. In conclusion, the results demonstrate the feasibility of NIR spectroscopy as taxonomic tool for classification of species that have morphological resemblance.BetulaBetula pendulaBetula pubescensB. pubescensB. pendula

Populus tremulaP. tremuloidesP. trichocarpaP. balsamiferaP. maximowicziirGErGE

Pruning was performed at midsummer in two genetically homogenous and managed planted silver birch stands in southern Sweden â one aged 9 and one aged 10 years. Wood defects were analysed 10 years thereafter, using the five uppermost twigs of the stems up to a height of 30 dm. The number of trees examined at each site was around 70, of which half were pruned. The main findings were that: a) compared to unpruned trees, pruned trees produced more defect-free wood outside the knots; b) most wood defects were found inside the knots; and c) wood defects like rot and bark ingrowth were similar for pruned and unpruned trees, while discolouration was marginally higher for pruned trees inside knots but similar outside knots. Overall, the results confirm previous findings that pruned birch trees will provide butt logs with higher value than unpruned trees.

The Nordic and Baltic countries are in the frontline of replacing fossil fuel with renewables. An important question is how forest management of the productive parts of this region can support a sustainable development of our societies in reaching low or carbon neutral conditions by 2050. This may involve a 70% increased consumption of biomass and waste to meet the goals. The present review concludes that a 50â100% increase of forest growth at the stand scale, relative to todayâs common level of forest productivity, is a realistic estimate within a stand rotation (~70Â years). Change of tree species, including the use of non-native species, tree breeding, introduction of high-productive systems with the opportunity to use nurse crops, fertilization and afforestation are powerful elements in an implementation and utilization of the potential. The productive forests of the Nordic and Baltic countries cover in total 63 million hectares, which corresponds to an average 51% land cover. The annual growth is 287 million m and the annual average harvest is 189 million m (65% of the growth). A short-term increase of wood-based bioenergy by utilizing more of the growth is estimated to be between 236 and 416 TWh depending on legislative and operational restrictions. Balanced priorities of forest functions and management aims such as nature conservation, biodiversity, recreation, game management, ground water protection etc. all need consideration. We believe that these aims may be combined at the landscape level in ways that do not conflict with the goals of reaching higher forest productivity and biomass production.33

Differences in the nutrient concentrations and nutrient amounts of stems and branches amongst clones of hybrid aspen (Populus tremula L. x P. tremuloides Michx.) were investigated. Seven clones with superior and seven with medium growth rates were selected from a test of 119 clones in southern Sweden. Four trees per clone were randomly identified and harvested in dormant conditions. Sample discs from the stems and branches were collected and analysed for N, K, P, Ca, Mg, and S concentrations, as well as wood density. The analyses revealed significant genetic differences in wood density, K, P, and Mg concentrations in the stems. There were weak (non-significant) and negative genetic correlations between stem volume and concentrations of all the nutrients, except potassium, suggesting that nutrient-efficient clones could be selected without significantly sacrificing genetic gain for growth. In the branches K, Ca, and Mg concentrations differed significantly among clones. After selecting more nutrient efficient clones, the potential savings of nutrients compared with current hybrid aspen material was estimated to be around 5%, which seems fairly low, at least in a short-term perspective. However, the use of clones with different nutrient storage strategies may be regarded as a possible way in the long run to save nutrients in hybrid aspen ecosystems, or of removing them when sludge is applied.

Ash dieback damage was assessed and analysed on 16–22 year-old grafts in two ash seed orchards (Fraxinus excelsiorL.). The grafts originated from 106 plus-tree clones selected from 27 stands in southern Sweden based on their phenotypes. The results obtained indicate that ash dieback disease is strongly genotypically controlled. There was considerable genotypic variation among individuals. None of the clones seemed to be totally resistant, but some exhibited reduced susceptibility and retained this resistance after 6 years under heavy infection pressure. Autumn phenology based on leaf coloration was subject to moderate genetic control (H2= 0.19). The genetic correlation between autumn phenology and damage was weak to moderate (rGfrom 0.38 to 0.60) and positive, indicating that susceptible clones have a prolonged growing season. There was no evidence suggesting that stands differed in susceptibility. Together with the high heritability of resistance, strong age×age correlations and weak genotype×environment interactions, this suggests there is good scope for breeding less susceptible trees for the future. [ABSTRACT FROM AUTHOR]

Field tests, each including 39–83 Swedish plus-tree clones of silver birch ( Betula pendula Roth) planted on 10 different sites in the southern part of Sweden, were evaluated at up to 10 years of age. The main conclusions can be summarized as follows. Growth traits were mostly under strong genetic influence, and showed substantial genetic variation and high potential genetic gain. Survival did not seem to be a trait of genetic importance. The genetic correlation between growth and growth cessation was weak, suggesting that it should be possible to find clones combining high growth and early autumn growth. Non-significant transfer effects for clones of different origin and weak G×E interaction were found, indicating that southern Sweden can be treated as a single utilization zone and that few sites are needed for genetic tests. Strong genetic age×age correlations were detected, suggesting that short test periods could be used. [ABSTRACT FROM AUTHOR]