Variability in young stands of Sitka spruce

Abstract

The aim of this project is to ascertain the variation in height growth, diameter growth and crown development, between individual stems in young stands of Sitka. Spruce (Picea sitchensis (Beng) Carr) up to canopy closure, to elucidate the development of the storied structure of the canopy, found at the time of first thinning. The variation in height, diameter, branchlet number and dry weight of root, shoot and needles of planting stock will be analysed. Similar measurements of height, height increment, diameter and branchlet number will be obtained in the 1-; 3-; 6- and 9-year old stands to assess the effect of transplant size on establishment and subsequent growth. At each age the height range will be divided into four equal vigour classes and the processes associated with the development of dominance will be examined. The spatial distribution of individuals of each vigour class will be analysed to determine whether the distribution is random or clumped.

The study originated from an interest in general stand development from time of planting to maturity, in relation to the effects of spacing and different grades of thinning, on the composition and performance of the vigour classes constituting the stand. Due to the time available, the study has been restricted to the determination of the variability within planting stock and its effect on establishment, subsequent growth and differentiation into vigour classes, within young stands up to time of canopy closure. It was decided to terminate the study at canopy closure, because the additional factors of crown and root competition which then become important, would constitute a separate study.

In order to reduce the variation from climatic and site factors, the areas of study were restricted to one general soil type, Peaty Gley, with a similar vegetation. To reduce altitudinal variation sites between 900- 1100 feet were chosen in the Wauchope Forest in the Scottish Borders.