Allocation of Dry Weight Increment in Crowns of Picea abies as Affected by Stand Nutrition

Abstract

Foliage and branch increments were estimated for individual branches from each major whorl within crowns of four unfertilised and four annually-fertilised trees. Maximum increments of new foliage and estimated branch wood plus bark growth occurred in the upper mid-crowns of both fertilised and unfertilised trees. The effects of position in crown were more pronounced in the fertilised trees which had fewer whorls of live branches. Individual needle weight measured on the first year's extension of each branch up to 10-yr-old branches suggested a 4% yr-1 increase in weight of individual needles aged two to five years followed by declines in weight in subsequent years. The ratio of estimated wood plus bark increment of branches to increment of current foliage was a minimum in the upper mid-crown. Allowing for possible increases in the weight of older needles reduced the within-crown variation. Total production of crown material per unit of foliage decreased dramatically down the crown with the influence of crown position being more pronounced in the fertilised trees.