Shoot Extension in Picea sitchensis I. Seasonal Variation Within a Forest Canopy

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Abstract
The seasonal variation of the daily increment of the shoots of 20-year-old Picea sitchensis is described. Data collected for leading shoots and those on the five topmost whorls of branches are compared qualitatively with seasonal trends in weather. Moving averages are used to describe the seasonal trend in daily extension rate and systematic variation through the canopy is noted in this trend. The fitting of Richards' growth functions to cumulative increment is described. The fitted growth curve described the seasonal trend of cumulative increment well on the basis of residual sums of squares, but systematic variation with time was noted in the residuals. Relative growth rate did not decline as a simple mathematical function of increasing size attained thus suggesting that simple determinate growth curves may not be appropriate in describing the growth of forest trees.