Allometric relationships for below- and aboveground biomass of young Scots pines

For 10-year-old Scots pine (Pinus sylvestris L.) trees allometric relationships describing branch and needle biomass at the branch level, as well as biomass of stems, branches, needles, coarse roots, small roots and total biomass at the tree level, were developed and compared. Height profiles of branch and needle biomass as well as biomass allocation were also analyzed. At the branch level, the relationships of branch diameter, branch length and whorl position were the best to predict branch and needle biomass. They were able to explain 96% of the observed variation for branches and needles. Simple allometric relationships of whorl height accurately predicted vertical distribution of branch and needle biomass as well as of their total, and explained more than 96% of the observed variation. The vertical distributions of biomass of branches, of needles and of their total, were very similar and were skewed vertically downward. At the tree level stem diameter at breast height (DBH) and tree height were significant determinants of biomass of stems, coarse roots and small roots. Similarly DBH, tree height and crown length were the predominant variables of biomass of branches and needles, and of the entire tree biomass. All together, allometric relationships with DBH were the best to estimate biomass of all above- and belowground compartments. These relationships were able to explain more than 98% of the observed variation. For 4.5–5.6 m tall trees with an average DBH of 7.16 cm, the entire tree biomass was 13.38 kg. On average 33.9% of the biomass was allocated to the stem, 25% to the branches, 22% to the needles, 17.8% to the coarse roots and 1.3% to small roots. The ratio of belowground biomass to aboveground biomass amounted to 0.26.