Morphometric, allometric, and developmentally adaptive traits in red spruce and black spruce. I. Species and seed-source variation

Abstract

The study objective was to compare intraspecific seed source and interspecifc variation of red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) BSP) in a number of morphometric, allometric, and adaptive traits. Analyses of variance for cotyledon number, root dry weight, shoot to root ratio, and seedling water balance revealed significant species effects. Germination time, total height, diameter, needle and stem wood dry weight, and survival had significant species effects and species × region interactions. Potential inbreeding depression effects were reflected in a positive relationship between height growth and percent germination and a negative relationship between height growth and germination time; these effects may have partly contributed to the species × region interactions. On average, 66% of the height growth difference between the species may be attributable to earlier germination and the other 34% to faster growth. Covariate allometric analysis showed that black spruce had a 39% higher shoot to root ratio than red spruce. Red spruce allocated 25% more dry weight (per unit needle weight) towards roots than did black spruce. When the resource sinks (stem wood and roots) are summed, black spruce is 8.6% more efficient at converting resources into sink biomass than is red spruce.