Deogratias M. Rweyongeza

Genetic Variation and Climatic Impacts on Survival and Growth of White Spruce in Alberta, Canada

Abstract Because climate has the greatest effect in determining the genetic structure of forest tree species, climatic variables with large effects on growth and survival need to be identified. This would enable proper matching of tree populations to planting sites in the present and future climates. We analysed 24-year survival (S24), height (H24) and diameter (D24) from a series of white spruce provenance trials with 46 populations and 8 test sites in Alberta, Canada. We determined: (1) the amount and pattern of genetic variation, (2) the response of populations to climatic transfer and (3) the potential effects of climate change (2030-2039) on H24 and S24 of the species in Alberta. We found that: (1) using the intraclass correlation, the between-population genetic variance was 10.6% (H24) and 6.6% (D24) of the betweenpopulation phenotypic variance across sites, (2) three climatic white spruce regions exist in Alberta within which variation in growth potential is strongly clinal, (3) the annual moisture index (AMI) expressed as a ratio of degree days above 5°C (GDD) and mean annual precipitation (MAP) was the major determinant of survival and growth at the test sites, (4) we found that at the level of AMI predicted for the 2030-2039 period, survival and growth would decline substantially in the continental part (northern and central) of Alberta where drought already exists. However, during the same period, survival and growth would increase substantially in the foothills and Rocky Mountains region where growth is currently limited by low GDD due to a short growing season.

Genetic parameters for seasonal height and height growth curves of white spruce seedlings and their implications to early selection

Abstract The logistic growth curves were fitted to seasonal cumulative height of white spruce seedlings taken at 14-day intervals to study genetic variation in seedling growth trajectories and their relationship to height growth in the field. To do this, seedlings were raised and measured in the greenhouse for 18 weeks. Observed heights were then used to fit growth curves. The observed heights, predicted height values, and growth curve parameters were subjected to statistical and genetic analysis. Height of 11-year-old trees from the same seed collection growing at two field sites in Alberta provided data for comparison with greenhouse traits. Analysis of variances and covariances showed that individual-tree heritability ( h i 2 ) and heritability of family means ( h f 2 ) for 18-week predicted seedling height (H18) were, respectively, 0.863±0.135 and 0.921±0.231. Heritabilities for the upper asymptotic height parameter ( k ) were 0.866±0.132 ( h i 2 ) and 0.921±0.232 ( h f 2 ). This shows that either H18 or k could be used to study genetic variation in the test material, since they both produced the same results. The rate of growth ( r ) and age at the point of inflection ( t 0.5 ) parameters had h i 2 of 0.242±0.062 ( r ) and 0.232±0.061 ( t 0.5 ), and h f 2 of 0.717±0.107 ( r ) and 0.712±0.105 ( t 0.5 ). Selection for H18 and k would, respectively, yield 50.8 and 51.7% of the genetic gain expected from direct selection for 11-year height at site A. The corresponding selection efficiencies for site B were 53.8 and 54.4%. These selection efficiencies show that selection for H18 and k in the greenhouse would be more efficient in improving gain per year than selection for 11-year field height. The use of seasonal seedling height growth curves in genetic studies and early selection is discussed.

Population differentiation and climatic adaptation for growth potential of white spruce (Picea glauca) in Alberta, Canada.

Abstract Genetic differentiation among white spruce populations in Alberta, Canada, was studied using time series data of height and diameter and a climatic index developed by principal component analysis. The objectives were to discern patterns of variation for growth potential and predicted optimum climate; compare optimum climate between populations, between height and diameter at the same age and between height or diameter at different ages; and to see if optimum climate differed from the climate inhabited by populations. Using cluster analysis we found that: (1) populations from mid-latitudes (54° - 57°N) and mid-elevations (600 - 800 m) were grouped together and exhibited high growth potential; populations from north of 57°N were grouped with those from elevations higher than 900m in the Rocky Mountains and exhibited low growth potential; and (2) With minor exceptions, populations from similar climates or geography were grouped together in terms of predicted optimum climate. (3) Analysis of variance showed that optimum climate differed significantly (P < 0.05) among populations; among heights at different ages; among diameters at different ages and between height and diameter at the same ages. However, there was no consistent trend in the direction of change in optimum climate with tree age. (4) The range of climate inhabited by the populations (PI₁ = -5.792 to 4.483) was much wider than the range of their predicted optimum climate (P̂Ō₁ = -1.001 to 0.842), which suggests that in terms of growth potential some populations inhabit sub-optimal climates. Implications of the results on management of white spruce in Alberta are discussed.

Heritability and correlations for biomass production and allocation in white spruce seedlings.

Abstract Tree growth is a multidimensional trait and families vary for components of growth such as height, diameter, foliage and roots. Therefore, variation in tree growth is better studied by analysing biomass production and allocation than simple traits. In addition, biomass is better linked to products such as pulp and wood energy than simple traits. We analysed biomass of 3-year old open-pollinated greenhouse seedlings of white spruce to determine (1) heritability for biomass production and allocation to shoot and root components, (2) correlations between biomass traits, and biomass traits with primary traits, and (3) correlation between biomass production in the greenhouse and height growth for the same families in the field. The study had a randomised complete block design with single-tree plots, 30 blocks and 58 open-pollinated families. Individual-tree heritability (hi2 ) and family mean heritability (hf2 ) ranged from 0.200 to 0.333 and 0.374 to 0.516 for green weight, respectively. Likewise, hi2 and hi2 ranged from 0.186 to 0.359 and 0.352 to 0.536 for dry weight, respectively. Genetic correlation (ra) between green and dry weight ranged from 0.943 to 1.015, while ra between shoot and root dry weight ranged from 0.947 to 0.955. In contrast, ra between biomass traits and field height ranged from -0.403 to -0.124. Thus, we conclude (1) variation in biomass production and allocation exhibited low genetic basis, (2) testing and selection for green or dry weight should lead to similar genotypes, (3) biomass allocation may not be easily altered by selection and breeding, and (4) indirect early selection based on seedling biomass

Genetic variation in height, branch and needle lengths of Pinus sylvestris L. from Siberia tested in Alberta, Canada

Summary We performed the analysis of variance and covariance on height, branch length, height to branch length ratio, and needle length measurements from thirty open-pollinated families of Pinus sylvestris L. from Siberia, Russia. This progeny trial was replicated on three sites in central Alberta, Canada. At six years from seeds, there was statistically significant variation for height, branch length to height ratio and needle length. On individual test sites, values of individual-tree heritability for height ranged from 0.20 to 0.35, whereas values of heritability for family means ranged from 0.41 to 0.59. These low to moderate heritabilities suggest that a combination of family and within-family selection would be effective in improving height growth for this population on individual sites. Across sites, values of individual-tree heritability for height ranged from 0.03 to 0.06, whereas values for heritability of family means ranged from 0.17 to 0.29. These low heritabilities across sites were due to high genotype by environment (GE) interaction. Analysis showed that 87% to 99% of the GE interaction was due to lack of genetic correlation among sites. Heterogeneity of the genetic variance among test sites contributed 1% to 13% of the GE interaction. This shows that families in this population of Scots pine are not broadly adapted and are therefore suitable only for a site-specific breeding programme. The paper also presents and discusses results of other traits with emphasis to breeding Scots pine for production of Christmas trees, which is the main use of this species in North America.