| Summary: | Given increased interest in harvesting lowland cedar-hemlock rainforests in the
Very Wet Hypermaritime Coastal Western Hemlock subzone of British Columbia, this
observational study was initiated to seek better understanding of how these forests
regenerate naturally, both in the absence of, and following, harvesting.
Plots were established in a clearcut and an immediately adjacent old-growth stand,
within which small trees (less than 1.3 m) were examined. Small tree presence, height,
and age distributions were constructed according to stand type, species, reproductive
origin, stand edge distance (in the clearcut), microtopography, substrate, soil moisture and
nutrient regime, and non-crop vegetation. Potential future crop trees per hectare were
also estimated.
Based on this study: 1) Ingress could not be relied upon to regenerate the
clearcut within 5-years, whereas advanced regeneration, some of which lacked apical
dominance of shoot terminal leaders, appeared to be important. 2) Proportionally more
veglings than seedlings reached 5-years of age and 30 cm in height. In the clearcut,
proportionally more Tsuga heterophylla than Thuja plicata reached 30 cm in height, and
advanced regeneration consisted of proportionally more Tsuga heterophylla than Thuja
plicata. 3) Proportionally more small trees occurred on Lignomor, mineral, and moss
substrates than on other substrates in both stand types. 4) Microtopographic influence
was related to substrate and soil moisture and nutrient regime, and differed between stand
types. In the clearcut, increased soil nutrient regime on inclines/mounds positively
influenced small tree presence and height growth beyond 30 cm, while increased soil
moisture regime on inclines/mounds negatively influenced height growth beyond 30 cm.
In the old-growth, proportionally fewer small trees reached 30 cm in height on
inclines/mounds, and proportionally fewer reached 5-years of age on wet organic or moss
substrates on inclines/mounds. 5) In the old-growth, increased soil nutrient regime
negatively influenced small tree presence, and increased soil moisture regime positively
influenced survival beyond 5 years. In the clearcut, increased soil nutrient regime
negatively influenced small tree height growth beyond 30 cm, yet positively influenced
height growth beyond 30 cm on Lignomors; increased soil moisture regime negatively
influenced survival beyond 5-years; and increased soil nutrient regime negatively
influenced Tsuga heterophylla survival beyond 5-years. 6) Blechnum spicant and
Calamagrostis nootkatensis were more extensive in the clearcut, and Blechnum spicant
negatively influenced small tree presence. Grass/sedge presence may also limit
regeneration.
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