Light regime beneath Sitka spruce plantations in northern Britain: preliminary results

Abstract Hemispherical photographs were taken in a range of Sitka spruce ( Picea sitchensis (Bong.) Carr.) stands in northern Britain. These were used to estimate the canopy gap fraction, and thereby estimate the transmission of light to the ground within each stand. Stands under routine management systems, whether thinned or unthinned, generally had too low a gap fraction to allow sufficient light through for seedling growth. The only stand with a gap fraction substantially higher than the others was a widely spaced (8 m) stand from a spacing experiment. The observations showed good agreement with a theoretical curve of canopy transmittance calculated using the Beer–Lambert law. The results indicate that a Sitka spruce stand should be thinned to a basal area 2  ha −1 , which is below management table stocking, if the gap fraction is to be increased to levels suitable for seedling growth.

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