POLLEN CONTAMINATION IN A SMALL BLACK SPRUCE SEEDLING SEED ORCHARD FOR 3 CONSECUTIVE YEARS

Pollen monitoring was conducted in 1987, 1988, and 1989 in the 2.8 ha Second Falls black spruce (Picea mariana (Mill.) B.S.P.) seedling seed orchard established in 1978. The objectives of the study were to evaluate (i) the orchard pollen-cone production, (ii) the level of orchard pollen production, and (iii) the level of pollen contamination for 3 consecutive years. Pollen traps were established around the orchard and collected on a daily basis. Pollen-cone production per tree averaged 3, 40, and 76 in 1987-1989, respectively. Pollen contamination during seed-cone receptivity was estimated to be 32%, 83%, and 58% in 1987, 1988 and 1989, respectively. The important increase in pollen contamination from 1987 to 1988 resulted, in part, from (i) the roguing of 40% of orchard trees and (ii) a 37-fold increase in pollen catch from contaminant sources from 1987 to 1988 compared to a 3.6-fold increase in pollen production by orchard trees. Supplemental mass pollination and synchronization of high orchard seed-cone and pollen-cone production with low pollen production from contaminant sources are suggested to reduce the level of pollen contamination, to increase panmixis and seed yield, and to maximize genetic gain.