Variation among black spruce clones in nutrient uptake and early growfh after field planting
A study was conducted to determine the genetic variation in black spruce (Picea mariana [Mill.]B.S.P) with respect to nutrient uptake and use efficiencyon a typical forest soil in central New Brunswick. The experimental stock originated from ten plus trees that had been selected in 1986 for the establishment of seed orchards. Seedling populations were raised from each plus-tree giving rise to ten half-sib families. From each of these populations ten plants were selected for vegetative reproduction by rooting shoot tips. In this way 98 clonal populations were obtained and field tested in a randomized block design. The plants were remeasured after completion of the first growing season. Since there was significant variation among families and clones at the time of planting, comparisons were made on the basis of annual growth increments and relative growth rates. Both families and clones varied significantly with respect to height and diameter growth, and gains in component and total plant weights. In all cases, clones contributed more to the total experimental variance than families. Biomass accretion was closely correlated with N and P uptake (r=0.911 and 0.892, respectively), suggesting that either one or both of the elements were limiting growth factors. Clones superior in growth and nutrient uptake had lower than average shoot:root ratios and, thus, higher than average root biomass. This would have provided the plants of these clones with an enlarged surface for nutrient absorption. Clones superior in growth also ranked highest in N and or P use efficiency, i.e., the amount of biomass produced per unit of element taken up. Fast-growing plants had accumulated the highest quantities of Al, but the bulk of it was retained in the roots. Aluminum uptake was further correlated with P uptake, suggesting that both elements moved towards the roots as a complex ion. KeyWords: Aluminum, genetic variation, clones, half-sib families, nutrient uptake, nutrient use efficiency, Picea mariana [Mill.]B.S.P.