Evaluation of phenotypic and physiologic characteristics of selected sources of white spruce, Picea glauca (Moench) Voss

Abstract

White spruce is highly valued for its wood pulp in commercial forestry in Minnesota. Seed orchards have been developed using genotypes selected for increased volume production. I conducted three different experiments to study the variation of ecophysiologic traits among genotypes selected from the Minnesota Tree Improvement Cooperative's program to better characterize the phenotype of selected genotypes. In chapter 1, I analyzed wood specific gravity, tree volume, and leaf traits on 25-year old trees in a white spruce progeny test. Wood specific gravity was negatively correlated with tree volume. Needle traits, primarily specific leaf area (SLA), leaf area ratio (LAR) and leaf mass ratio (LMR), were positively correlated with wood volume. In chapter 2, I planted seedlings from four genotypes selected for superior volume growth and two wild sources in a common garden. I harvested ten trees from each genotype, each year for three years. I examined biomass allocation, tree allometry and assessed genetic correlations among allocation of biomass to major organs. The largest differences in biomass were found between the two wild sources that represented two different seed zones in Minnesota. Selected sources more closely resembled the southern, than the northern, wild source. The northern wild sources had slightly higher allocation to roots but otherwise no significant differences in allometry were found. In chapter 3, I set up an outdoor experiment by planting five selected- and two wild- seed sources into 1-gallon containers to test the effects of mid-winter warming on phenology and growth of white spruce. Bud-break time was delayed in plots that were warmed in February, and advanced in those warmed in March. Overall controls had the highest height growth and intermediate bud-break time. Climatic warming that takes place during winter months may delay or advance bud-break depending on the timing. Growth of white spruce is expected to decline with increased episodes of winter warming. Selected sources should be favored in reforestation across Minnesota because of the higher productivity and adaptability to local conditions.