Allometric relationships on biomass and needle area of Douglas-fir

Abstract

The aims of the study were: (1) to establish allometric relationships among stem and crown dimensions, biomass, and needle area; (2) to describe the above-ground dry matter distribution; (3) to determine the relationship between sapwood area and needle area; and (4) to describe the vertical distribution of tree needle area and branch biomass. Twenty-three trees out of four stands were sampled. Strong stand-independent correlations were found between stem and crown dimensions. Stem diameter at breast height (dbh) was non-linearly related to tree height, and linearly related to crown radius. Tree biomass generally increased with increasing dbh. The relationship between stem biomass and dbh was stand-independent, but the relationship between crown biomass and dbh clearly differed between the stands. Best results were obtained after two-sided logarithmic transformations. The ratio between needle biomass and branch biomass significantly decreased with increasing tree size. Dry matter distribution differed between trees from different crown classes: suppressed trees had relatively less crown biomass. Specific needle area decreased with needle ageing and increased from tree top to crown base. SLA strongly varied within trees, but not between trees: needle biomass was strongly linearly related to needle area. Needle area was linearly correlated with sapwood cross-sectional area at breast height: ratio differences could be ascribed to differences in crown base height. Vertical locations of the maximum needle area density (m 2 m −3) and branch biomass density (kg m −3) differed, reflecting the increase of the needle biomass/branch biomass ratio when moving upward in the crown. Location of the maximum density depended on canopy closure, but was generally below the middle of the crown.