Canadian Forest Service Publications
Germination ecology in mountain hemlock (Tsuga mertensiana (Bong.) Carr.) 2001. El-Kassaby, Y.A.; Edwards, D.G.W. Forest ecology and management 144: 183-188.
Issued by: Pacific Forestry Centre
Catalog ID: 18071
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The effect of variable heat sums (440, 400, 320 and 280° h days), expressed as alternating temperatures (25/15, 20/15, 20/10 and 15/10°C over 8/16 h (day/night) regimes), and various stratification treatments (0, 4, 8 and 12 weeks) and their interactions on germination, were investigated using eight natural-stand seedlots of mountain hemlock (Tsuga mertensiana [Bong.] Carr.). The alternating temperature regimes were obtained using a computerized thermogradient system. Temperature/heat sums difference and seedlot differences had major impacts on germination. The most rapid and complete germination occurred under the highest two heat sums. Stratification showed no effect on germination under any of the experimental conditions. Significant interactions in germination parameters were observed only between temperatures x seedlots. All other interactions were minor and judged to have little biological and/or practical importance. A prerequisite for good natural regeneration depends on the presence of favorable germination environments coupled with good seed crops. These requirements are infrequent, and explain the commonly-observed poor stocking levels achieved by natural regeneration alone in this species. Thus, artificial regeneration is recommended to augment natural regeneration to reach acceptable stocking levels and ensure gene pool conservation of mountain hemlock.