Canopy Structure and Leaf Area Index in a Mature Scots Pine Forest

Abstract

The projected leaf area index (LAI) of a mature stand of Scots pine ( Pinus sylvestris L.) at Thetford Forest, south-east England was measured by sampling the needle populations on harvested and wind-thrown trees covering the range of girth sizes. The vertical distribution of leaf area for individual trees was polymodal while that for the canopy as a whole was adequately described by the curve for a normal distribution with the inclusion of a term for positive skewness. The fitted curve defined the midpoint of the canopy at a height of 14.3 m and the standard deviation of leaf area with respect to height as 13% of the canopy depth. The fitted curve explained 90 per cent of the variation and the estimates of the parameters were close to the measured values. Using previous measurements showing that needle production and fall could be described by linear regression equations, a model was developed to predict the annual changes of current and old needles in a closed canopy. The maximum LAI at Thetford was 2.73 on 12th August of which 36 per cent was new (current) needles. Leaf area index varied by only 7 per cent between November to May inclusive; higher values occurred between June and October at times of potentially high photosynthetic and transpiration rates. The leaf characteristics of the stand were similar to those of a stand of Scots pine of similar age at Roseisle in north-east Scotland.