Editing Spruce (section)

=== Growth ===
Spruce seedlings are most susceptible immediately following [[germination]], and remain highly susceptible through to the following spring. More than half of spruce seedling mortality probably occurs during the first growing season and is also very high during the first winter,<ref name="alex">Alexander, R.R. (1987). Ecology, silviculture, and management of the Engelmann spruce–subalpine fir type in the central and southern Rocky Mountains. USDA, For. Serv., Washington DC, Agric. Handb. 659. 144 p.</ref> when seedlings are subjected to freezing damage, frost heaving and erosion, as well as smothering by litter and snow-pressed vegetation. Seedlings that germinate late in the growing season are particularly vulnerable because they are tiny and have not had time to [[Hardiness (plants)|harden off]] fully.

Mortality rates generally decrease sharply thereafter, but losses often remain high for some years. "Establishment" is a subjective concept based on the idea that once a seedling has successfully reached a certain size, not much is likely to prevent its further development. Criteria vary, of course, but Noble and Ronco (1978),<ref name="nob">Noble, D.L.; Ronco, F. (1978). Seedfall and establishment of Engelmann spruce and subalpine fir in clearcut openings in Colorado. USDA, For. Serv., Rocky Mountain For. Range Exp. Sta., Res. Pap. RM-200. 12 p.</ref> for instance, considered that seedlings four to five years old, or 8&nbsp;cm to 10&nbsp;cm tall, warranted the designation "established", since only unusual factors such as [[Phacidiaceae|snow mold]], [[Wildfire|fire]], [[Disturbance (ecology)|trampling]], or predation would then impair regeneration success. Eis (1967)<ref name="eis">{{cite journal|author=Eis, S. |year=1967|title= Establishment and early development of white spruce in the interior of British Columbia|journal= For. Chron.|volume= 43|issue=2|pages=174–177|doi=10.5558/tfc43174-2|doi-access=free}}</ref> suggested that in dry habitats on either mineral soil or litter seedbeds a 3-year-old seedling may be considered established; in moist habitats, seedlings may need 4 or 5 years to become established on mineral soil, possibly longer on litter seedbeds.

Growth remains very slow for several to many years. Three years after [[Shelterwood cutting|shelterwood felling]] in subalpine Alberta, dominant [[Regeneration (biology)|regeneration]] averaged 5.5&nbsp;cm in height in [[Scarification|scarified]] blocks, and 7.3&nbsp;cm in non-scarified blocks (Day 1970),<ref name="day2">Day, M.W.; Rudolph, V.J. (1970). Development of a white spruce plantation. Michigan State Univ., Agric. Exp. Sta., East Lansing MI, Res. Pap. 111. 4 p.</ref> possibly reflecting diminished fertility with the removal of the A horizon.