DIRECT SEEDING OF BLACK SPRUCE IN NORTHWESTERN ONTARIO - TEMPORAL CHANGES IN SEEDBED COVERAGE AND RECEPTIVITY

Temporal changes in black spruce (Picea mariana [Mill.] B.S.P.) seedbe d coverage and seedbed receptivity were investigated on coarse-texture d upland sites near Thunder Bay (48 degrees 25'N 89 degrees 15'W), in northwestern Ontario. Sowing was completed in May for three consecutiv e years following summer scarification at each of 12 sites. Infilling by organic debris reduced the proportion of receptive soil strata thre e to five years after scarification by 50-95%. Receptive seedbed cover age declined more quickly on fresh Soil Moisture Regimes with a variet y of deciduous trees and shrubs than on moist Soil Moisture Regimes do minated by eracaceous shrubs. Pioneer mosses, which are also good seed beds, invaded moist sites more readily than fresh sites, and mitigated losses in seedbed coverage. Compact Sphagnum seedbeds in lowland depr essions maintained good areal coverage much longer than did receptive upland soil strata. Seedling establishment ratios varied greatly among seeding years, seedbeds and sites, but there was an underlying trend of decreasing seedbed receptivity with time since scarification. Seedl ings originating from the first seeding year were taller at age 7-10 t han those originating from the second or third seeding years.