Juvenile white spruce (Picea glauca (Moench) Voss) under an aspen (Pop
ulus tremuloides Michx.) overstory were studied in nine boreal mixedwo
od stands in west-central Alberta. In each stand, 50 understory white
spruce were cut for stem analysis al ground level, 30, 70, 130 cm, and
every 100 cm to tree height. Tn four stands, recruitment of these und
erstory spruce occurred immediately after the disturbance, while in ot
hers the recruitment was delayed several decades. The period of recrui
tment was as short, as 15-20 years or continued for decades, producing
an uneven-aged understory. Trees initiated on rotten logs had a sligh
tly lower initial annual diameter increment but did not differ in heig
ht growth compared with those initiated on normal forest floor. The an
nual height increment increased as the trees grew in height, presumabl
y as they overtopped successive layers of shading vegetation. When see
dlings were less than 30 cm tall they grew less than 10 cm per year, b
ut attained growth rates of 30 cm per year or more when they were tall
er than 230 cm. Height growth rates for these understory trees were co
mparable to reported growth rates of white spruce of similar size and
age from clearcut areas.