Specific leaf area and needle weight of Norway spruce (Piceaabies) in stands of different densities

Abstract

During an investigation on the effects of differing stand densities on biomass distribution, owing to thinning in 17-year-old Norway spruce stands, specific leaf area (SLA) and 100-needle dry mass were measured for three diameter at breast height (DBH) classes, five canopy sections, and two needle age-classes. Mean SLA was found to be 50 ± 17 cm²/g. High correlation of SLA and 100-needle dry mass with DBH, crown position, and needle age was found. Older needles had a lower mean SLA than the current years needles, while they did not differ significantly in their 100-needles dry mass. Thinning proved to be a minor factor for foliage variability, since DBH, which is dependent upon thinning and the trees competitive status, explained a major part of variation in leaf morphology. A third-degree polynomial regression function could be developed to predict SLA from 100-needle dry mass. This function shows wide validity. It applies to all DBH classes and crown sections. It also shows good fit for older trees from totally different sites. To predict the total leaf area of a crown stratum, only the dry mass of 100 needles and the total needle biomass of the stratum must be known.