Björn Hannrup

Genetic parameters of growth and wood quality traits in Picea abies

Genetic parameters were estimated for wood and growth traits in two 19-yr-old clonal trials and a 40-yr-old full-sib progeny trial of Norway spruce [Picea abies (L.) Karst.]. In the clonal trials high (>0.4) broad-sense heritabilities were found for wood density traits, lignin content, number of internal cracks, growth traits, spiral grain and number of resin canals. Moderate (0.2–0.4) heritabilities were found for tracheid lumen diameter and cell wall thickness, microfibril angle and tracheid length, while low heritabilities (<0.2) were found for pulp yield, fibre strength, wood stiffness and wood colour. Lignin content and pulp yield showed low genetic variation, whereas the genotypic coefficient of variation for most other traits ranged between 5 and 15%. Most traits showed low levels of genotype by environment interaction. Among the wood properties, latewood proportion, earlywood density and ring density showed significant, adverse correlations with volume in both clonal trials.

Genetic correlations among wood, growth capacity and stem traits in Pinus sylvestris.

Wood density and tracheid length are two traits that significantly affect wood products. Genetic correlations were estimated to evaluate the effect on these traits from a selection for traits included in the Swedish Pinus sylvestris L. breeding programme. Measurements from a non-contiguous single-tree plot progeny trial with controlled matings between 30 parent trees was used. Heritabilities were high for the wood traits, intermediate for the growth capacity traits and low for the stem traits, with the exception of branch angle. Wood density showed no or non-significant negative genetic correlations with the growth capacity traits and a positive correlation with relative branch diameter. Tracheid length showed positive genetic correlations with height and a positive correlation with relative branch diameter. A selection that increased height growth at the age of 13 yrs by 10% was expected to decrease mean wood density at 33 yrs by 1%. The expected correlated response to tracheid length from the same selection was a 3% increase in the juvenile and mature wood.

Genetic variation and relationships to growth traits for microfibril angle, wood density and modulus of elasticity in a Picea abies clonal trial in southern Sweden

Abstract Genetic variation in wood density, microfibril angle (MFA), wood stiffness (MOE), height, diameter and volume was investigated in a 26-year-old Norway spruce [(Picea abies (L.) Karst.] clonal trial in southern Sweden. Wood quality measurements were performed on 10 mm increment cores using SilviScan. For MFA, mean values of annual rings showed the highest value (30°) at ring 2 counting from the pith, followed by a steep decrease and a gradual stabilization around ring 12 at approximately 14°. MOE showed a monotonic increase from 5 GPa to 14 GPa when moving from pith to bark. High broad-sense heritability values were found for wood density (0.48), MFA (0.41) and MOE (0.50). All growth traits displayed heritability values of similar magnitudes as reported in earlier studies. The generally high age–age correlations between different sections of the wood cores suggested that early selection for wood quality traits would be successful. Owing to unfavorable genetic correlations between volume and MOE, the correlated response indicated that selection for volume only at age 10 would result in a 0.27% decrease in weighted MOE at age 26 for every 1% increase in volume.

Summer drought and low earlywood density induce intra-annual radial cracks in conifers

Abstract Intra-annual radial cracks in conifers have a major impact on the quality of wood. However, the exact cause of their formation is still unclear. Some authors have proposed summer drought as the main cause of these cracks, whereas others have proposed winter desiccation. Wood from Picea abies trees grown at different sites in Europe (Italy, Switzerland and Sweden) was analysed. Radial cracks always occurred within one tree ring. Tree rings with lower earlywood density had a higher number of radial cracks. Combining the results from different sites, evidence was found that cracking occurred during severe summer droughts, characterized by high water deficits, probably because the hydrostatic tension within the tracheids exceeded the fracture limits of the middle lamella. According to these observations cracks may occur after a drought in any tree ring located in the sapwood that is characterized by a low earlywood density, with the exception of the outermost one. In conclusion, cracks cannot be used to date drought events at an annual resolution.

Genotype by Environment Interaction in Pinus sylvestris L. in Southern Sweden

Abstract To estimate the amount of genotype by environment interaction (G x E) data was obtained within the Swedish breeding program of Pinus sylvestris L. The calculations were based on estimates of G x E expressed by the genetic correlations across trials. In total, 66 progeny trials were included coming from 17 different test series. The number of parents tested per progeny trial was in average 52. Some parents were tested in several series and in total 812 parents were represented in the study. The results of our study showed that the amount of G x E for growth traits in Pinus sylvestris in southern Sweden was low. The median genetic correlation across trials for height, height increment and diameter were in the range 0.75-0.80 and the pattern of interaction was largely unpredictable from site differences in site index, latitude, longitude and altitude.

Comparing gain and optimum test size from progeny testing and phenotypic selection in Pinus sylvestris

The profit from tree breeding is dependent on the amount of money invested and how these resources are spent, particularly in the testing of selection candidates. Simulations of within-family selection were used to find the optimum balance among the number of candidates, progenies per candidate, and test sites for a given investment level and to compare the profit from progeny testing and phenotypic selection. The simulations were based on genetic parameters estimated from 66 Pinus sylvestris L. progeny trials in southern Sweden and on compilations of breeding costs. For progeny testing the optimum number of candidates and test sites increased with increasing investment level, whereas the number of progenies per candidate and site decreased and stabilized at ca. 10 individuals. The maximum annual profit for the phenotypic selection was higher and occurred at a lower investment level than for progeny testing. Among the two alternatives of progeny testing studied, the intensive alternative with practices to...

Wood stiffness and strength as selection traits for sawn timber in Acacia auriculiformis

Acacia auriculiformis A. Cunn. ex Benth. is an important planting tree species, but little attention has been paid to its wood properties, such as shrinkage, stiffness, strength, and basic density, which are important for use in structural and appearance-grade timber applications. Here we report the genetic variation in static bending stiffness and strength of wood in a 5½-year-old clone trial in southern Vietnam and the genotypic correlations among these traits and tree diameter, wood shrinkage, and basic density. There was significant variation in stiffness and strength among 40 randomly selected clones. Clonal repeatability (H2) was high for stiffness and moderate for strength. There was no consistent pattern of difference between heartwood and sapwood for the estimates of H2 for stiffness and strength, whereas the estimates of H2 were lower for heartwood density than for sapwood density. Diameter showed a significant negative genotypic correlation with stiffness but a nonsignificant correlation with s...

Use of wood shrinkage characteristics in breeding of fast-grown Acacia auriculiformis A. Cunn. ex Benth in Vietnam

Abstractu| li]• Genotypic variation in wood total and partial shrinkage, basic density and growth traits was estimated in 51÷2 year old Acacia auriculiformis trees in a clonal test. li]• In the tangential, radial and longitudinal directions, the mean values were 2.64%, 1.64% and 0.77% for partial shrinkage, and 5.92%, 3.23%, and 0.96% for total shrinkage, respectively. Total and partial transverse shrinkage were significantly greater in sapwood than in heartwood. li]• Clonal repeatability (HC2) estimates for partial shrinkage were lower than those for total shrinkage, and heartwood shrinkages had lower HC2 than those for sapwood. Estimates of HC2 were from 0.32 to 0.38 for total transverse shrinkage, comparable to HC2 for both total and partial volumetric shrinkages (0.40 and 0.32, respectively). However, HC2 for longitudinal shrinkages, total and partial coefficients of anisotropy were only from 0.09 to 0.18. li]• The genotypic coefficients of variation of all shrinkage traits varied from 5.45% to 8.02%. Total shrinkage was strongly positively correlated with partial shrinkage in each dimension. Genotypic correlations were not significant between shrinkage and growth traits or density. Strong and significant correlations between transverse shrinkage in heartwood and sapwood (0.87) indicated that juvenile shrinkage is a good genetic indicator of this trait in older trees.Utilisation du retrait du bois dans l’amélioration de l’Acacia auriculiformis A. Cunn. ex Benth à croissance rapide au Vietnam.Résumé• Nous avons estimé la variation génotypique, des retraits partiels et totaux, de la densité du bois ainsi que des traits de croissance dans un test clonal d’Acacia auriculiformis âgé de cinq ans et demi.• Les retraits partiels (à 12 % d’humidité) dans les directions tangentielle, radiale et longitudinale sont respectivement de 2,64 %, 1,64 % et 0,77 % tandis que les retraits totaux (à l’état anhydre) sont respectivement de 5,92 %, 3,23 % et 0,96 %. Les retraits partiels et totaux transverses sont significativement plus élevés dans l’aubier que dans le bois de cœur.• Les estimations de la répétabilité clonale (HC2) pour les retraits partiels sont plus faibles que celles obtenues pour les retrait totaux et les retraits du bois de cœur ont une plus faible (HC2) que ceux de l’aubier. Les estimations de (HC2) sont de 0,32 et 0,38 pour le retrait transverse total, valeurs comparables à (HC2) pour les retraits volumétriques total et partiel (respectivement 0,4 et 0,32). Cependant (HC2) pour les retraits longitudinaux total et partiels ainsi que pour les coefficients d’anisotropie total et partiels, varient seulement de 0,09 à 0,18.• Les coefficients génotypique de variation de tous les types de retraits varient de 5,45 % à 8,42 %. Les retraits totaux sont fortement corrélés positivement avec les retraits partiels de chaque direction. Les corrélations génotypiques entre les retraits et les traits de croissance ou la densité ne sont pas significatives. Les corrélations importantes et significatives entre le retrait transverse du bois de cœur et de l’aubier (0,87) indiquent que le retrait juvénile est un bon indicateur génétique de ce trait dans les arbres plus âgés.

A decision support model for individual tree stump harvesting options based on criteria for economic return and environmental protection

ABSTRACT Based on principles of multi-criteria analysis techniques, a model (MAPStump-E) for decision support on stump harvesting at stand level was developed. The model applies the concept that each stump can be attributed production values (economic) and environmental values (here soil protection and water quality). Individual tree stump information was incorporated directly from the production reports of harvesters and combined with high-resolution Geographical Information System data on topography and soil type to create a production submodel and a soil and water vulnerability submodel (SWM). To test the model, it was applied to a 45-ha study forest in south-central Sweden and the outcome of nine scenarios with varying bioenergy prices and environmental protection levels was examined. Combined analysis of the effects of production and environmental criteria on total dry mass of harvestable stumps at the study site showed that biomass prices had a stronger influence than environmental criteria. Conflict stumps were defined as stumps suitable for harvest based on production criteria, but unsuitable based on soil and water protection criteria. In a “medium” price scenario, the proportion of conflict stumps at the study site ranged from 6% to 18%, depending on protection level set.

Genetic variation in responses of Pinus sylvestris trees to natural infection by Gremmeniella abietina

Abstract In 2001 large areas of Pinus sylvestris L. stands in Sweden were attacked by Gremmeniella abietina (Lagerb.) Morelet. The resultant damage was assessed in five genetic field trials and one clonal seed orchard, with the aims of quantifying the genetic variation in tree responses to G. abietina, studying the genetic relationship between G. abietina susceptibility and growth traits, and examining the implications of the results for P. sylvestris breeding. A comparison of G. abietina damage between plus-tree progenies and seed stand check-lots in each of four tree classes (dominant, co-dominant, subordinated and suppressed) found no significant differences except in the suppressed tree class, where plus-tree progenies were damaged less severely than trees from the seed stands. Narrow- and broad-sense heritability for G. abietina damage traits were in the range 0.22–0.42. Genetic correlations between G. abietina damage and growth traits were weak and not significantly different from zero. The results imply that selection for growth capacity in P. sylvestris breeding programmes using plus-tree selection or field progeny tests does not increase susceptibility to G. abietina. In addition, there is scope for selecting genotypes with increased resistance if this is required in the future.