Canadian Forest Service Publications
Growth response of western hemlock and Douglas-fir seedlings to temperature regimes during day and night. 1971. Brix, H. Canadian Journal of Botany 49(2): 289-294.
Issued by: Pacific Forestry Centre
Catalog ID: 28350
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Growth of western hemlock and Douglas-fir seedlings was studied under 11 controlled day–night temperature regimes ranging from 8 to 28 °C, and with light intensities of 450 and 1000 ft-c for 100 days after seed germination. Production and distribution of dry matter, together with length and diameter of stem, were measured. Douglas fir had a broad optimum temperature for growth between 18 and 24 °C, whereas hemlock had a pronounced optimum at 18 °C, especially at high light. High temperature was more detrimental to growth of hemlock than of Douglas fir. At 28 °C, dry matter production of hemlock was 7, and of Douglas fir 40% of the maximum. Low temperature similarly affected the two plants. A constant day–night temperature regime was as good or better than alternating temperatures for both plants. Day temperature was more effective in increasing growth than night temperature. Light intensity, for most temperature regimes, had a pronounced effect on dry matter production, less on stem diameter, and little or none on stem length. Dry matter production of hemlock was considerably lower than for Douglas fir for all growing conditions.